Is Woad A Weed – How To Kill Woad Plants In Your Garden
By: Bonnie L. Grant, Certified Urban Agriculturist
Without woad plants, the deep indigo blue of ancient history would not have been possible. Who knows who discovered the plant’s coloring properties but it is now known as dyer’s woad. It is rarely used as a dye in the modern textile industry, but woad is now naturalized in much of North America, although it is native to Europe. If you need help getting rid of woad, then this article may help.
Tips on Woad Control
We all seem to have a different notion of what is a weed. Personally, I feel a plant is a weed if it is invasive, choking out other plants or in the wrong location. Other gardeners may feel differently. For instance, a plant may be a weed if it is ugly, too big, or even has a bad odor.
Woad grows wild in roadsides, ditches, pastures, fields, forest edges and almost any other open space. It is a very competitive plant that can colonize rapidly. In cultivated landscapes, controlling dyer’s woad is important or the plant may gradually take over.
If you have decided woad is a weed, it is time to do something about it. Woad propagates itself though seed. An average plant produces 500 seeds (although some can exceed 1,000 seeds), which will disperse in a wide radius, establishing new colonies quickly.
In warm to temperate regions, the plant is a short-lived perennial and can reproduce several times before finally dying back. Manual woad control is difficult due to the plant’s deep taproot. The thick root can grow up to 5 feet (1.5 m.) deep, so controlling dyer’s woad by digging can be difficult.
How to Kill Woad That is Out of Control
Hand pulling can diminish the root’s strength, although the tough plant will usually return. Seed is dispersed by wind, water, animals and machines. Cutting off the blooms before they turn to seed will minimize the spread of woad. Sowing weed-free seed and feeding livestock with weed-free hay can also help reduce the impact of the plant.
In some situations, repeated tilling of an area is an effective way of getting rid of woad. Equipment and tool sanitation after use in a field contaminated with woad also reduces the spread of the plant. A rust fungus, Puccinia thlaspeos, will cause leaf distortion, stunting, and chlorosis, which diminishes woad’s vitality and can eventually control the plant.
Chemicals are a step of last resort, especially in food crops. There are several listed chemicals that are effective against woad plants. These need to be applied when seedlings are young for best control. Remember to follow all instructions when using chemicals and apply sprays when wind is calm and never near plants that can be harmed by the formula.
Most state extension services will have guidelines on what and how to use herbicide chemicals safely for both the applier and the environment.
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Dogs and humans team up to help eradicate Dyer’s woad in Montana
BOZEMAN – A Labrador that’s trained to find cadavers, and a Border collie plucked from a Bozeman animal shelter are now helping rid Montana of noxious weeds.
Demonstrating her abilities on a frosty fall morning, Wibaux the Labrador scrambled up a Montana mountain and soon detected the scent of Dyer’s woad over the smell of hikers, pets, deer, shrubs and other plants. Shaking with excitement but true to her training, Wibaux circled the weed, barked continually and finally sat down until her handler verified that she had, indeed, found Dyer’s woad.
“Good dog. Good girl,” Deb Tirmenstein said as she handed Wibaux a biscuit.
Tirmenstein marked the location on her GPS unit and said she would return alone later to spray the weed. It’s a trip she has made many times since she, Wibaux and a Border collie named Seamus joined the Dyer’s woad project in 2011.
The project grew out of research conducted at Montana State University and has multiple goals, according to weed experts at MSU, the University of Montana and Beaverhead County.
One goal is to completely eradicate Dyer’s woad from Montana by using dogs and humans together. Amber Burch, assistant weed coordinator for Beaverhead County and coordinator of a statewide effort to fight Dyer’s woad, said the weed is native to southeast Russia and used to be cultivated in England as a source of blue dye and medicine. It was first identified in Montana in 1934. It is now classified as a Priority 1B Noxious Weed in Montana.
One Dyer’s woad plant can grow four inches in a week and produce as many as many as 10,000 seeds, Burch said. UM Natural Areas Specialist Marilyn Marler said the roots sometimes go down for more than five feet. When blooming, the plant can grow waist high. Noxious weeds compete with native plants and can overrun pastures and wildlife habitat.
Dyer’s woad experts said the weed is extremely widespread in Utah and eastern Idaho, but it is a good candidate for eradication in Montana because it is far less widespread in this state. Once found in 17 Montana counties, Dyer’s woad is now active in only seven because of the Montana Dyer’s Woad Cooperative Project started in 1984. The Montana counties with active Dyer’s woad are Beaverhead, Silver Bow, Carbon, Flathead, Gallatin, Missoula and Park County.
Dyer’s woad in Montana has decreased 87.1 percent since 2005, Burch said. At last count for 2012, the total number of plants in the state was 997. A site is considered eradicated if no Dyer’s woad plants are found in eight years. If a single plant is found during that time, the site is deemed eradicated as long as the plant doesn’t produce seeds.
Another goal of the weed-dog project is to spread the word that that dogs and humans can find more weeds together than alone.
Kim Goodwin, a research associate in the Department of Land Resources and Environmental Sciences in MSU’s College of Agriculture, started investigating the possibility of using dogs to detect noxious weeds when she was a master’s degree student at MSU. She started her master’s degree in 2005 and finished in 2010. Before that, in the 1980s, former MSU Extension Noxious Weed Specialist Pete Fay researched herbicides that might be used on Dyer’s woad. He had MSU students, personnel and county weed crews pulling Dyer’s woad. He started the Montana Dyer’s Woad Cooperative Project.
Goodwin’s research showed that dogs and people complement each other when looking for noxious weeds. People are good at finding large flowering plants and large patches of noxious weeds, but they can overlook individual weeds. Dogs work best in areas of low-density, high-priority weeds. They can smell Dyer’s woad even when the weed is a tiny rosette hidden by other types of plants. They can smell Dyer’s woad when it’s underground and a mere fragment of a root.
“Through our research, we found they are able to detect twice as many small plants as the surveyors do,” Goodwin said.
The third goal of the weed experts is to find more locations for their applied weed-dog research.
“We are interested in determining how to turn this discovery into something useful for land managers,” Goodwin said.
The effort that involves Wibaux and Seamus is based on Mount Sentinel at the east edge of Missoula. Marler, the natural areas specialist for UM, said it has been hard to control noxious weeds there because the mountain is steep and the study area covers 200 acres. Major progress has occurred in the past 12 years, however, because of city, county and UM cooperation.
Wibaux and Seamus joined the Mount Sentinel effort in 2011 and continued in 2012. MSU provided funding the first year. Goodwin is still a collaborator on the project, which is headed by Marler.
This year on Mount Sentinel, the dogs detected about 40 locations that humans missed, Goodwin said. The researchers discovered that by having humans look for Dyer’s woad first. A day or more later, the dogs covered the same area. By comparing those numbers, they measured the dogs’ usefulness.
“It showed the dogs do have utility,” Goodwin said.
Goodwin said she got the idea for using dogs to detect noxious weeds after reading about the federal “Beagle Brigade.” In it, the USDA’s Animal and Plant Health Inspection Service (APHIS) uses beagles to inspect luggage and boxes at U.S. airports and ports of entry. Since dogs also detect land mines and have been used for thousands of years to hunt, she wanted to see if dogs could detect noxious weeds, too.
Goodwin used German shepherds in her master’s degree research because of their intelligence and scent-work experience, Goodwin said. The Mount Sentinel project shows that a Labrador and Border collie can also detect noxious weeds. In this case, the weeds are Dyer’s woad. Goodwin’s earlier research focused on spotted knapweed.
Wibaux was already trained to find human remains when she was recruited to detect Dyer’s woad, said her owner, Tirmenstein. She has searched for cadavers and has assisted law enforcement in Montana, Washington, Idaho, Arkansas and elsewhere.
Aimee Hurt, director of operations for Working Dogs for Conservation, said the Montana-based organization that uses Wibaux for noxious weeds, sends dogs all over the world to detect such smells as gorilla dung, cheetahs, and emerald ash borer beetles. The training to detect cadavers, noxious weeds, narcotics and scat is all very similar, she added.
Trainers introduced Wibaux to Dyer’s woad by hiding the weed inside a box with holes in the lid and placing the box next to boxes containing other weeds. When Wibaux realized she would receive a treat or get to retrieve a ball every time she detected Dyer’s woad, she started honing in on it. Her training became longer and more complex until she was able to detect Dyer’s woad outdoors in a larger environment without getting distracted or confused.
Seamus came to Working Dogs for Conservation from Heart of the Valley Animal Shelter in Gallatin County, Hurt said. Noting that only one or two dogs in a thousand make good detection dogs, she said Seamus stood out from the others because he was playful even when surrounded by chaos. A closer look showed that he had other qualities that could be developed to make him into a successful detection dog.
“These dogs tend to be highly energetic and easy to motivate with food or toys,” Hurt explained.
They also don’t mind seeking the same thing over and over. They love working with a handler. They love rewards no matter if they receive them 60 times a day or once. They aren’t confused by competing scents. They aren’t distracted.
“We are asking a lot of them, but they really love it,” Hurt said. “We work with dogs that need a job to be happy.”
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BOTANICAL AND ECOLOGICAL CHARACTERISTICS
GENERAL BOTANICAL CHARACTERISTICS:
Botanical description: Dyer's woad is typically a biennial [21,27,28,31,32,33,36,40] or a short-lived, usually monocarpic, perennial [21,28,31,32,33,36,40]. A review by Callihan and others  and a laboratory study by Asghari  suggest that buds on Dyer's woad root crowns sometimes survive after the plant has flowered, allowing the plants to persist and possibly produce additional flower and seed crops (see Vegetative regeneration). Dyer's woad is sometimes described as a winter annual [36,54,69]. A field study on northern Utah rangeland found that most Dyer's woad individuals were biennial or monocarpic perennials, but none displayed winter annual life histories. All Dyer's woad plants that set seed died [20,21]. A second study in the same area found that 1% of Dyer's woad individuals studied flowered during the first growing season .
Aboveground description: Dyer's woad begins as a rosette with several long-petioled basal leaves [23,27,31,32,33,40] about 1.6 to 4 inches (4-10 cm) long on average [23,40] but reaching up to 7 inches (18 cm) long [31,32,33,82] and 0.3 to 1.6 inches (0.8-4 cm) wide . Basal leaves are usually covered with simple hairs [31,82]. According to Varga and Evans , approximately 20 stalks begin to develop from each rosette, but usually 7 or fewer mature. Other sources indicate that Dyer's woad usually has 1 main stem [27,31,32,33] that is simple below and branched above [31,32,33]. Stems are erect and may range from about 14 inches (35 cm)  to 47 inches (120 cm) tall [27,31,32,33], with several authors describing a typical range of 20 to 35 inches (50-90 cm) tall [23,40,74]. Plants are typically glabrous throughout [23,27,33,40,82] or hirsute with long, simple hairs at the base . Stem leaves are narrower than basal leaves, mostly about 1 to 4 inches (2-10 cm) long , and are gradually reduced upwards .
Dyer's woad flowers are about 6 mm wide  with petals about 3.5 mm long [31,32,33]. Flowers are borne in numerous, compound racemes forming a large, terminal panicle [27,31,32,33,36]. Dyer's woad fruits are samaroid, indehiscent silicles ranging from 8 to 18 mm long and 2.5 to 7 mm wide with a single, median seed [27,28,31,32,33,36,40,74]. Silicles have strongly flattened valves [27,28,32,33] and are sometimes described as winged (, review by ). Fruits are dark to black at maturity [31,36,74] and droop from a short, slender pedicel  that is ascending to reflexed  or recurved . According to Weber , Dyer's woad is the only crucifer that produces hanging, indehiscent fruit resembling samaras of Fraxinus.
A 1983 field survey of Dyer's woad in Idaho revealed some morphological variation: Some Dyer's woad plants in Bear Lake County had very long basal leaves and were more pubescent than others described elsewhere. One specimen of Dyer's woad along North Canyon in Caribou County was almost 5 feet (150 cm) tall. At Border Summit on dry and gravelly soils at 6,300 feet (1,920 m), Dyer's woad was generally shorter (16 to 24 inches (40-60 cm) tall) and denser than those observed in other areas. A rust fungus was observed on some Dyer's woad plants in Caribou and Bear Lake counties: Infected plants appeared severely stunted, though the disease was not of epidemic proportions on these sites . The fungus was later identified as Puccinia thlaspeos, and has been recorded on other weedy members of the Brassicaceae in North America ( and references therein). See Biological control for more information on this rust fungus.
Belowground description: The root system of Dyer's woad is dominated by a taproot [20,21] that is variously described as "robust" , "thick" , "fleshy" , or "woody" . Dyer's woad taproots can reach or exceed 5 feet (1.5 m) in depth (, review by ). Smaller lateral roots are concentrated in the upper 8 to 12 inches (20-30 cm) of the soil profile (, review by ) and spread laterally about 16 inches (40 cm) . The root system of Dyer's woad in a foothill rangeland pasture in northern Utah that had been continuously grazed by domestic sheep for over a decade had a mean taproot length of about 35 inches (90 cm) for rosettes and about 39 inches (100 cm) for mature plants. Mean total root length was about 85 inches (217 cm) for rosettes and 102 inches (258 cm) for mature plants, although the measurement method used (trench profile method) underestimates total root length because most of the fine roots are lost. Mature Dyer's woad plants had 43% of total mapped root length in the upper 8 inches (20 cm) of the soil profile, while rosettes had 31% of total mapped root length at this depth, suggesting that lateral branching of Dyer's woad roots occurs predominantly in the second year of growth. The authors note that this 2-layered rooting pattern is similar to that of sagebrush (Artemisia spp.), which may confer an advantage in semidesert steppe in the Intermountain West [20,21].
Dyer's woad plants collected from disturbed sites in Utah were nonmycorrhizal this was expected because members of the Brassicaceae family are predominantly nonmycorrhizal .
Dyer's woad is characterized by rapid vegetative growth during spring that typically enables it to produce seed by late spring or early summer on midelevation sites. The period of rapid growth by Dyer's woad may overlap with the period of peak water extraction by bluebunch wheatgrass on some sites in some years, suggesting there may be belowground interference between these co-occurring species  (see Successional Status). Dyer's woad plants were studied on northern Utah foothill sites at 4,850 to 5,000 feet (1,480-1,525 m) elevation during 2 studies: one from May 1982 to November 1983, and the other during the 1984 growing season. See Seedling establishment and plant growth for similar information from an experimentally established Dyer's woad population in the same area. Young Dyer's woad plants were marked and phenologically categorized between May 1982 and November 1983. Phenological stages were as follows: dormant, leaf growth, stem growth, floral buds developing, flowering, seed development, seed ripening, seed dissemination, and dead. Leaf growth occurred in both fall and spring, and flowering occurred in late spring. Time between stem growth and seed development was about 8 weeks. Mean stem growth was about 4 inches (10 cm) per week from mid-April until the end of May. Plants were dormant in both summer and winter, corresponding with hot, dry conditions or cold temperatures, respectively. Sixty-five percent of marked plants died and 1% flowered during the 1st growing season. Of the 35% that survived to the 2nd year, about half flowered and produced fruit. All plants that set seeds died about 12% remained vegetative and may have produced fruit in the 3rd year .
Dyer's woad plants observed on Utah foothill sites during the 1984 growing season started vegetative growth by 16 April 1984, less than 1 week after snowmelt. Basal diameter increased between 16 April and 7 May and thereafter remained fairly constant. Likewise, rosette diameter increased during the same period, leveled off by 23 May, and then declined as basal leaves withered and flowering stems developed. Stem growth began during the last week of April, and flowering began the second week of May, reaching its peak about 23 May. Height of flowering stalks increased rapidly between 7 May and 11 June. Seed developed between 9 June and 15 June. By the end of June, most of the seeds had ripened .
Root crown buds on Dyer's woad plants that have flowered sometimes survive, allowing plants to persist and flower again. The growth of the flowering shoot reduces carbohydrates stored in the taproot during the previous season (review by ).
Typical flowering dates by geographic area are given in the following table:
|Dyer's woad flowering dates by geographic area|
|California||April to June |
|Illinois||May to June |
|Nevada||April to July |
|Utah (Uinta Basin)||May to July |
|Virginia||May to June |
|Intermountain West||May to June |
|Northeast and adjacent Canada||May to July |
|Pacific Northwest||April to August |
Dyer's woad fruits ripen between June and October throughout its range . Dyer's woad seeds become viable relatively early during seed production .
A survey in Idaho in 1983 found that timing of flowering and seed dispersal were related to elevation. Flowering and dispersal dates observed in that survey were as follows :
|Phenology of Dyer's woad in several counties at different elevations in Idaho |
|County||Elevation (m)||Phenological stage||Dates|
|Northern Bannock||1,829||Rosette and bolting||3 June|
|Northern Bannock||up to 1,402||Flowering||23 May|
|Jefferson and Bonneville||1,341-1,463||Flowering||26 May|
|Bear Lake||2,256||Flowering||as late as 14 July|
|Caribou||below 1,981||Full bloom||17 June|
|Bear Lake||2,256||Full bloom||29 June|
|Central and southern Bannock and Franklin||--||Full bloom||7 June|
|Franklin county||1,585||Full to late bloom||10 June|
|Eastern Oneida||1,067||Late bloom to seed set||15 June|
|Clark||1,707-2,012||Late bloom to ripe fruit||22 July|
|Adams||899||Dispersing ripe fruit||26-28 July|
|Blaine||1,295||Dispersing ripe fruit||26-28 July|
|Southwestern Oneida||1,492-1,463||Dispersing ripe fruit||20 July|
Dyer's woad reproduces by seed. It may sprout following damage to aboveground parts, and sometimes after flowering (see Vegetative regeneration) however, persistence and spread of Dyer's woad populations is dependent on viable seed production.
Pollination and breeding system: Results from laboratory studies in Italy showed an outcrossing breeding system in Dyer's woad. The effects of selfing and crossing on seed production, germinability, and progeny growth were assessed. Self-pollinated plants produced fewer siliques (7.1 g/plant) with lower weight (6.0 mg) and lower seed germinability (8.2%) than outcrossed plants (44.1 g, 8.0 mg, and 46% for each character, respectively). Self-pollinated progenies generally showed lower height growth than outcrossed progenies .
Flower and seed production: Dyer's woad requires a cold vernalization period to induce flowering. A greenhouse study in Utah found that both 1-year old Dyer's woad plants that had previously flowered (crown rosettes) and 4-month old seedling rosettes required exposure to cold temperatures (39 °F (4 °C) or less) for a minimum of 23 to 47 days to induce flowering [3,4]. The 2 types of rosette responded differently to cold treatments, which ranged from 0 to 93 days at 39 °F (4 °C), suggesting that cold tolerance is dependent not only on length of cold exposure but also on plant age. No seedling rosettes died during any length of cold exposure, while 50% of crown rosettes died after 93 days of cold exposure, and 30% died after 47 days of cold exposure. There was no difference in survival of crown rosettes after 23 days of cold exposure and that of controls . Continual disturbance, such as defoliation, delays flowering of Dyer's woad  (see Physical or mechanical control).
Reviews describe "prolific" or "abundant" seed production in Dyer's woad [12,19,54]. A review by McConnell and others  suggests that some plants produced more than 10,000 seeds in 1 year, although the source of this information is not given. Dyer's woad plants studied on Utah rangelands produced about 350 to 500 seeds each [20,21].
Seed production may vary among plants established in different seasons and on different microsites. A field study in Utah found that Dyer's woad plants that established in fall had slightly larger rosettes, taller flowering stalks, and produced more fruit (563 fruits/plant) than those that established in spring (345 fruits/plant). Mean fruit production of plants established in spring was similar among plants growing near sagebrush (293 fruits/plant) and those growing in interspace microsites (317 fruits/plant). Fruit weights were similar among all groups (3.9 mg/fruit) [20,21]. In a related study in the same area, average fruit production was 383 fruits/plant .
Seed dispersal: Dyer's woad fruits do not release the seed at maturity, but fall to the ground intact . The majority of Dyer's woad fruits disperse within a few meters of parent plants. Long-distance dispersal may occur with the aid of humans, livestock, wildlife, and water .
Most Dyer's woad fruits shed soon after reaching maturity, although some remain on the plants until winter. Fruits are firmly attached to plants, and some abrasive force such as wind or rain is needed to detach them. A field study in Utah recorded daily Dyer's woad fruit dispersal from 25 June 1985 until 27 August 1985. Most of the fruits were shed in the first 10 days of the study thereafter, the dispersal rate declined substantially, leveling off after 4.5 weeks. Ninety-five percent of all trapped fruits fell within 21 inches (54 cm) of parent plants, and mean dispersal distance was positively correlated with the height at which seeds were released (r²=0.85). The greatest distance that fruits traveled via wind was about 8 feet (2.4 m). The relationship between windspeed and number of fruits dispersed was "poor" however, most fruits scattered in the direction of prevailing winds. Dyer's woad fruits remaining on plants until winter may disperse much greater distances when blown over the surface of crusted snow [20,21]. Fruits may be further transported by ants, as was observed during studies on Utah rangelands .
Long-distance spread of Dyer's woad fruits and seeds must be aided by vectors such as humans, livestock, wildlife, and water. Humans may disperse fruits in their clothing, vehicles, tools or machinery [20,21,80]. Roadsides and railways are effective avenues of seed dispersal . Long-distance dispersal is likely when Dyer's woad seed is a contaminant in alfalfa or other crop seed (review by ) or when mature, seed-bearing Dyer's woad plants are cut and baled with alfalfa in infested fields, and this baled hay is shipped to where it is used as livestock feed [19,20,21]. Contaminated hay is one of the major causes of Dyer's woad spread .
Livestock and wildlife may carry fruits in mud on their hooves or in their fur . The curved pedicel of Dyer's woad fruits may act as a hook to aid in dispersal by animals. Dyer's woad fruits remaining on plants past the first snowfall may be dispersed by herds of deer and elk in the winter months, when herd use of foothill sites is highest . Farah  speculates that a high incidence of Dyer's woad infestations on south-facing slopes on Utah rangeland may be related to deer and elk use of these sites in winter. Birds and rodents may also contribute to long-range dispersal of Dyer's woad .
Downhill and downstream dispersal of Dyer's woad fruits may be aided by water flattened wings facilitate this mode of dispersal. Dyer's woad populations along the banks of drainage systems in Utah may have established after this type of dispersal [20,21].
Seed banking: Information on seed banking in Dyer's woad was lacking, and it had not been determined how long seeds are viable in the soil, as of 2009. Anecdotal accounts from Europe suggest that Dyer's woad sometimes appears after grasslands are tilled authors contend that these are sites of former woad crops where the seeds have remained dormant in the soil, presumably for many years (King 1966 as cited by ).
While Dyer's woad seeds may have no dormancy, they are contained in fruits that have water soluble germination inhibitors such that few seeds germinate immediately in the field, presumably until the inhibitors are leached from the fruit . The inhibitors in the fruit may allow Dyer's woad seed to persist in the soil seed bank . Because the inhibitors are removed by leaching, they do not seem likely to contribute to long-term persistence of seed in the soil, because they would be leached by precipitation, allowing germination under favorable conditions .
Evidence from field studies indicates that some Dyer's woad seeds remain viable in the soil for at least 10 to 12 months. Dyer's woad fruits (1,200 total) were harvested from a Utah study site on 8 July 1982 and buried under about 0.4 inch (1 cm) of soil. Each month, 120 fruits were removed from the field, and seeds were removed from fruits and tested for germination and viability. Germination tests were conducted at 77 °F (25 °C) with 12 hours each of alternating light and darkness, and germinated and viable seeds were counted after 14 days. Germination rates of Dyer's woad seed stored in the field ranged from 99% in September 1982 (after 1 month of burial) to 44% in May 1983 (after 9 months of burial). Seed viability remained high, fluctuating between 73% and 100%, and did not decrease over time. Whether Dyer's woad seed can germinate after being stored in the soil longer than 10 months is not known. In a related study on the same site, Germination: Dyer's woad seeds separated from the fruits do not exhibit dormancy and readily germinate under a variety of conditions, though they do not readily germinate when they remain intact within the fruit. Dyer's woad seeds do not usually dehisce from the fruits under field conditions thus, the intact fruit imposes dormancy . The majority of Dyer's woad seeds collected in August 1969 and separated from the fruits germinated after incubation for 168 hours at temperatures from 37 to 77 °F (3-25 °C). Conversely, when intact fruits were incubated, germination was low and erratic. Seedlings elongated much more slowly from fruits than from seeds .
Reduced germination and seedling elongation from intact fruits were likely due to chemistry rather than due to a physical obstruction. In a laboratory study, not only were germination and seedling emergence reduced from intact Dyer's woad fruits, but the presence of intact fruits or fruit leachate also reduced germination and seedling emergence in both threshed Dyer's woad seed and in seeds of several other species (see Successional Status for details). Washing Dyer's woad fruits in tap water for 48 hours increased germination, and washing fruits for 96 hours almost eliminated germination inhibition. In the field, some Dyer's woad seedlings established from fruits that overwintered .
Germination inhibitors present in freshly sown seed are likely leached over winter, thereby allowing greater germination of overwintered seeds. In a field study in Utah, germination of Dyer's woad seeds sown in October 1984 was 10 times higher in spring 1985 than fall 1984. The author speculates that seeds that germinated shortly after being sown may have been in damaged fruits .
Dyer's woad seed germination is likely inhibited by shade. High percentages (>85%) of Dyer's woad seed germinated under red, yellow, and white light within 4 days. Significantly lower percentages germinated under far red and blue light (15% and 37%, respectively) (P Seedling establishment and plant growth: Seedling establishment, survivorship, growth, and eventual reproductive output (see Seed production) may vary among Dyer's woad seedlings established in the fall versus those established in spring, and among microsites. Dyer's woad population demographics were studied over a 2-year period on a Utah rangeland where 100,000 Dyer's woad fruits were collected during the summer of 1984 and sown on 8 September 1984 in a "well-vegetated" area lacking Dyer's woad. During the study period precipitation was 18% above the estimated long-term average, and mean monthly temperatures were slightly below the long-term average [20,21]. The following information comes primarily from this single study and is therefore limited in scope Dyer's woad may display different population dynamics on other sites. See Seasonal development for more precise phenological information from Dyer's woad populations in the same area.
Seedling establishment: For freshly shed seeds, establishment rates were lower 1 month after sowing in the fall (0.3%) than during the following spring (2.7%) [20,21], which is consistent with findings of Young and Evans  that Dyer's woad fruits contain water-soluble germination-inhibiting substances that would have leached over winter. Germination in fall 1985 was twice that in fall 1984 these differences were not associated with differences in either precipitation or mean monthly temperatures. Germination from the original seed input ceased after fall 1985 [20,21] (see Seed banking).
Microsites near sagebrush plants seem to provide a more favorable microenvironment for Dyer's woad seedling establishment than interspace microsites. Seedling densities were 170 and 26 Dyer's woad plants/m² on sagebrush and interspace microsites, respectively [20,21].
Survival: Survivorship patterns were similar in fall- and spring-established Dyer's woad populations, with peak mortality in summer. Cohorts of Dyer's woad that established in October 1984 (n=285) experienced little mortality during the following winter, slight mortality in early spring 1985, and peak mortality during the summer. Thirty-six of these plants survived the summer drought, overwintered again, flowered, and set seed in spring of 1986. None of the Dyer's woad seedlings that established during the spring of 1985 (n=2,664) flowered in the same year. Of the spring-established cohort, 371 individuals survived the summer drought and overwintered. Eighty-seven percent of these plants flowered and produced seeds in spring of 1986, and the other 13% remained vegetative. Peak mortality in both Dyer's woad populations occurred during a period with high temperatures and negligible precipitation, suggesting that the main source of mortality was water stress there was no evidence of predation or pathogens. The authors note that the developing roots of young rosettes of Dyer's woad are unlikely to access soil moisture from deep soil layers, where moisture occurs during hot and dry conditions above ground but they caution that a causal relationship between seedling mortality and soil moisture deficit was not established because soil water content was not measured [20,21].
A life table analysis for Dyer's woad showed constriction of population growth at 2 transitions: seed to seedling (establishment) and young rosettes to mature rosettes. The establishment rate was 3% and only 23% of young rosettes survived to mature rosettes. Once plants became mature rosettes, the probability of surviving to reproduce was 81%. All flowering individuals set seed, with an average fruit production of 496 fruits/plant [20,21].
Neither microsite characteristics nor seedling density appeared to impact mortality rates in Dyer's woad populations. Mortality of Dyer's woad plants growing near sagebrush and those in the interspaces were similar (73% and 74% respectively), despite a 7-fold difference in seedling density [20,21].
Growth and reproductive output: Fall germination of Dyer's woad favors both vegetative growth and reproductive output (see Seed production) however, spring germination was more important than fall germination in terms of overall population growth: Higher germination rates in spring resulted in more individual plants and higher total fruit production from spring-germinated cohorts than fall-germinated cohorts. Fall-germinated individuals had nominally greater rosette sizes than spring-germinated individuals during most of the study period, and differences were most pronounced at the start of the spring 1986 growing season. Stem growth was initiated in both cohorts during the last week of March 1986, and rapid stem growth occurred up to 18 May 1986. By 20 April, the fall cohort was taller. The fall cohort had significantly greater fruit production/plant (P Vegetative regeneration: Several sources indicate that Dyer's woad plants may sprout when the top growth is removed at ground level [19,20,21,36,67]. Sprouting seems to originate from buds on Dyer's woad root crowns (, review by , personal communication ). Numerous vague references to vegetative or asexual regeneration in Dyer's woad were found in the literature: "Clonal growth has been observed but is not common"  "Asexual reproduction may occur from this underground root system"  ". the weed can spread from underground portions of the root system. "  "It has a large fleshy taproot from which it may reproduce asexually"  and "Damaged plants often resprout from buds located on the root crown and, less frequently, from the roots" . However, vegetative regeneration in Dyer's woad seems to be restricted to sprouting from the root crown following aboveground damage.
Dyer's woad is likely to survive and sprout following aboveground damage and defoliation [19,20,21,36,67], depending on timing, frequency, and severity of damage. A review by Evans  states that while undisturbed Dyer's woad plants typically behave as biennials or winter annuals, perennial behavior can be elicited by mowing, hand-pulling, or breaking the bolting stalk above ground. This is supported by evidence from a field study where plants were clipped at varying intensities, frequencies, and dates: Significant mortality and reduction in reproductive performance occurred when at least 60% of the aboveground phytomass had been removed on or after 23 May (P SITE CHARACTERISTICS:
In the western United States, Dyer's woad most commonly establishes and persists on rangelands and disturbed sites such as roadsides, rights-of-way, fence rows, uncultivated croplands (e.g., alfalfa and small grain fields, orchards), pastures, old fields, and "waste places" ([17,28,31,32,36,82], reviews by [19,54]). Characteristics of sites supporting Dyer's woad in eastern North America were not described in available literature (2009). A Virginia flora describes Dyer's woad as infrequent and occurring on disturbed sites .
Climate: Dyer's woad is native to parts of Russia, where the climate may be similar to that of the Intermountain West (review by ). Few studies of Dyer's woad report climate data. On study sites where Dyer's woad occurred on coarse, well-drained soils at 2 foothill locations on the western slope of the Wellsville Mountains in northern Utah, mean annual precipitation is 16 inches (400 mm), and mean annual air temperature is °F (9 °C) [21,84]. A review by Parker  suggests that Dyer's woad has a moisture requirement of 14 to 18 inches (356-457 mm) per year. Specimens of Dyer's woad were collected at 40 xeric to mesic sites in Idaho .
Elevation : Elevations ranges for Dyer's woad were given for the following areas:
Although many sources suggest that Dyer's woad is well suited to coarse, rocky soils with low water-holding capacity (reviews by [2,19,59,80]), Dyer's woad grew larger and had greater nitrate aquisition on a relatively moist site with fine soil textures than on a drier, coarse textured soil in a Utah field study (see table below) . Differences in these variables were not related to proximity, life form, or diversity of neighboring plants (see Successional Status).
Establishment in early succession: In a small-plot (1.5 × 1.5 m) experiment Dyer's woad seedling establishment was consistently higher in disturbed than undisturbed plots regardless of growth form composition of plots. Plots were composed of 24 plants of either crested wheatgrass (Agropyron cristatum × A. desertorum), western yarrow (Achillea millefolium) or Wyoming big sagebrush (Artemisia tridentata var. wyomingensis), and were either left intact or disturbed by removing 4 plants from the center and lightly scarifying with a rake. Four hundred Dyer's woad seeds were sown in each plot. Dyer's woad seedling density was 52% to 66% higher in disturbed plots than intact plots (P Persistence: Dyer's woad can establish and persist on many types of anthropogenically disturbed sites (see Site Characteristics), and commonly occurs on semi-arid rangelands with a long history of livestock grazing (e.g., ). A review by DiTomaso  lists Dyer's woad among nonnative plants that tend to be avoided by livestock, which can favor a rapid shift in dominant species in grazed rangeland plant communities where these unpalatable plants occur. Another review by Parker  classified Dyer's woad as an "invader" in terms of its response to grazing. Field studies in northern Utah [20,84] indicate that Dyer's woad is readily grazed by domestic sheep prior to flowering however, little damage is done to the plants (see Biological control).
Competition experiments on old fields in Utah suggest traits in Dyer's woad that facilitate its persistence in disturbed, semiarid shrub-steppe ecosystems. In a greenhouse experiment, Dyer's woad exhibited low plasticity in response to nitrogen availability, suggesting a low nitrogen requirement, low nitrogen productivity, or both. The authors note that these qualities are associated with the ability of a species to survive and persist under stressed, nutrient-poor conditions . In a similar experiment, nitrate acquisition of Dyer's woad was less than that of crested wheatgrass, greater than that of big sagebrush (P Establishment and persistence in late succession: Evidence of Dyer's woad's ability to invade established vegetation comes from field studies in Utah [20,21] and California . In a "well-vegetated" area on a Utah rangeland that had not been grazed by livestock for several decades, Dyer's woad established from seed sown by researchers [20,21]. In a study in northern California , Dyer's woad established in annual grass communities considered "ecologically closed" . These annual grasslands, dominated by medusahead or cheatgrass, were thought to represent a culmination of plant succession, and invasion and dominance by Dyer's woad prompted an investigation into the mechanism allowing its establishment (see Allelopathy).
Results from small-plot experiments in Utah suggest that sites supporting a diversity of species or life forms may be more resistant to Dyer's woad establishment than those dominated by single species or life form. Species used were a combination of native sagebrush-steppe species and nonnative species widely used for revegetation within sagebrush-steppe communities. Dyer's woad seedling establishment was consistently higher in single-species (western yarrow) forb plots than in 4-species forb plots, mixed life form plots (consisting of grasses, forbs and shrubs), or single-species shrub (Wyoming big sagebrush) plots. Dyer's woad establishment was consistently higher in 4-species shrub plots than 4-species forb plots. Dyer's woad establishment in single-species grass plots (crested wheatgrass) and 4-species grass plots was inconsistent between years .
Shade tolerance: While Dyer's woad tends to occur on open, sunny sites (see Habitat Types and Plant Communities and Site Characteristics), it exhibits some degree of shade tolerance. Callihan and others  note Dyer's woad occurrence in many types of plant communities in Idaho, including those dominated by trees and large shrubs. In the greenhouse, Dyer's woad responded to increased shade through morphological modifications (increased leaf area, specific leaf area, and shoot:root ratio) to improve its light-harvesting ability. These responses may favor the ability to establish and persist on harsh, nutrient-poor sites as well as shaded, undisturbed sites. Dyer's woad also demonstrated morphological plasticity in response to variable water conditions, especially under shaded conditions. The authors suggest that high plasticity in heterogeneous environments may allow Dyer's woad to establish and spread into new sites without the lag time required for local adaptation . However, germination of Dyer's woad seeds may be inhibited by shade .
Allelopathy: Laboratory studies suggest that Dyer's woad fruits probably contain allelopathic substances , although the allelopathic chemicals have not been identified. In the laboratory, the presence of Dyer's woad fruits inhibited germination of Dyer's woad, tumble mustard (Sisymbrium altissimum), and alfalfa seeds reduced root length in seedlings of Dyer's woad, tumble mustard, medusahead, cheatgrass, and alfalfa and reduced shoot length in seedlings of Dyer's woad and tumble mustard. Germination and root length were also reduced for several species incubated on substrates treated with Dyer's woad fruit leachate, as shown in the table below. Medusahead responded similarly, although data were not provided .
Because Dyer's woad produces a large number of fruits, and these fruits seem to suppress germination of associated species, successional trajectories may be altered in communities dominated by Dyer's woad, with Dyer's woad maintaining dominance by reducing establishment of other species. As a biennial or short-lived perennial, Dyer's woad does not have to establish seedlings every year to maintain dominance in annual communities. The researchers noted, however, that some annual grasses established in Dyer's woad stands in the field .
My idea of a good day
My idea of a really good day is getting things done. Winter solstice has passed and we are finally getting more daytime light. This weekend I managed my usual weekend laundry, garden weeding and did a small woad vat.
[left to right: yellow #2 exhaust bath, cactus fruit, woad, woad over-dyed with fennel.]
I’ve been working on onion baths, first one for the darker color – tangerine-orange – and exhaust the remaining dye for lighter yellow. [The pinkish-orange was my previously mentioned cactus fruit attempt.
[upper left clockwise: onion with a 15 min copper after-bath, onion #1 bath, cactus fruit, onion #2 exhaust bath.]
I’ve tried 1:1 (fiber:dye stuff) but have found that 1:.5) works well too even if I have to let it sit longer. First bath simmers for an hour, sits over night and then the 2nd exhaust bath is another hour of simmering and again cooling over night.
More Adventures with Woad and Weld or where have all the Dicots gone
gone to Eudicots every one…
Since I spend a lot of my so-called spare time working with or around plants – dye plants especially – I decided it was time to understand how they work. This fall I signed up for “Botany for Gardeners” at my local university extension program. (Brian Capon’s Botany for Gardeners – a very good read.)
Possible conversation starter: apparently with all the DNA sequencing there has been a shakeup up in botanical classification. The dicots (two-leaf seedling thing vs the one-leaf monocot thing) some of us grew up with (and had a couple of semesters ago) are now eudicots (new two-leaf seedling thing). Who knew.
My standard dye plants are often categorized as “weeds” so I end up babying along other people’s unwanted garden invaders, Wood Sorrel/Oxalis, Fennel, etc. Recently I’ve been nursing along (what better be) the next batch Woad and Weld.
End of summer, Woad vat, cotton, corn and beans
I don’t know how official this is but most people I know consider “Labor Day” – which in the US falls on the first monday of September – as the end of summer. I ended my summer with a Woad vat. The wool is my SCHG challenge recycling/upcycling project.
Starting from the left: Woad overdye Hibiscus (yellow) Woad overdye onion peel (orange-yellow) Woad multi-dipped Woad one dip.
I had hoped to grow my own Woad but as it turned out I was growing Weld. (Oh don’t ask, so much for my plant identification skills…)
This Woad was purchased in powder from from Woad Inc in the UK. The All About Woad site has really excellent directions and also sells Woad dye and kits.
Besides the dye plants (my project) there is the family vegetable garden. Most years we get a supply of dried tomatoes and soup beans. This year we tried growing corn. Besides what was eaten fresh and given away we have dried corn (soup, cornbread, etc.).
[dried -> ground -> corn bread]
And the first boll on my cotton shrub just started opening.
Eat corn bread, contemplate the Woad vat, not a bad ending for the summer.
Summer and Fennel
In some areas Fennel is considered a noxious and/or invasive weed. But for me, Fennel has always been a nice, well-behaved multi-use plant. It even smells good in the dye pot. (And I can identify it correctly : see post about the Woad that turned out to be Weld.)
Fennel has also become one of of my seasonal markers. Wood Sorrel runs through half of the year and as it dies off the Fennel starts up. And visa versa. So I am always stocked with yellow dye.
Quick note: Fennel by my experience works only well with protein fiber (i.e. wool), I’ve never successfully dyed plant fiber such as cotton. Wood Sorrel on the other hand dyes anything I’ve tried. The only exception has been corn fiber.
The Woad that is actually (Dyers) Weld
This is embarrassing. It’s what happens when you grow a plant that you have never actually observed from seed to dye pot. The Woad I thought I was growing is really Dyer’s Weld. Yellow not blue. More yellow. A really good, clear Lemon yellow but still more yellow.
Before it began to bloom it could have been either.
However, as it blossomed it became obvious that the plant I had was not what I thought it was. Checked every image I could find including the Druid Plant Oracle and I definitely was not growing Woad.
So I’ve got Weld, Dyer’s Weld. Nice looking plant. The bees seem to like it. Works on wool (protine fibers – so not cotton).
Southern California is experiencing the usual drought conditions and never having liked or wanted a lawn I’ve been slowly extending the kitchen herb garden out from the front of the porch and over what would be lawn. This eliminates lawn and leaves more room for Lavendar and Basil to run rampant. For watering I’ve been dumping my dish water and any reasonable gray water so the lavendar, sage, basil, woad and sundry odd herbs are thriving inspite of the dry spells.
Obviously one Woad plant won’t dye too much but I plan to save some seeds for next season. It’s also been interesting seeing how it grows. Nice looking plant.
I have however purchased some powderd Woad from http://www.woad.org.uk/. Seems like a good informative site.
Another site I’ve been reading through is the Woad Page.
In the meantime my Woad plant seems to be thriving on a combination of drought, Santa Ana winds, dish water and Trader Joe’s Next to Godliness non-phosphate dish soap.
Woad and more Fennel (or return of the Fennel)
The surviving Woad plant from last year. It really started growing this spring and looks about ready to bloom.
If you haven’t hear the Woad Song here is at least one version: http://www.youtube.com/watch?v=KK5-F9mLp4Y
The Oxalis has died off for the season and the Fennel is blooming. (Sorry there isn’t a Fennel song..)
Woad: woad and ‘volunteer’ basil
The woad continues growing out and now up. In one of the pots some volunteer basil appeard, which means Pesto sauce as well as blue dye.
I wasn’t sure how the particular plant would manage in a hot, dry (Southern California) climate. It seemed to start out slow last fall and really took off around the beginning of summer.
Should anyone else be interested, here are a couple of Woad sites:
Rowan’s Woad Page
Yahoo Group: woadgrowers
Woad and fennel
Around the time that the Oxalis was dying off the Fennel seemed to take off. It looks like I won’t be scavenging the Smart-&-Final parking lot or sides of freeways for Fennel this year. The backyard stand – now too large to be called a shrub – is producing enough to keep me in dye and local insects in food.
Also here, my first attempt at growing Woad. There are 2 plants, still in pots. One seems to have some Sweet Basil growing along side – probably from some other planting. They are about 6” across right now. I’m not sure how fast these grow but it is unlikely there will be blue dye until next season.