Thigmomorphogenesis Info: Why Should I Tickle My Plants
By: Ilana Goldowitz Jimenez, Plant Scientist & Writer
Have you heard of tickling plants to help them grow? If you saw someone tickling, stroking, or repetitively bending plants, you might assume they were crazy. But these exact practices have been adopted in some commercial greenhouses and nurseries. By tickling plants, these growers are taking advantage of something called thigmomorphogenesis, a little-known phenomenon that affects how plants grow.
“Why should I tickle my plants?” you may wonder. This article will explain the reasons behind this unusual practice.
So, what is thigmomorphogenesis? Plants respond to light, gravity, and moisture levels, and they also respond to touch. In nature, a growing plant encounters rain, wind, and passing animals. Many plants detect and respond to these touch stimuli by slowing their growth rate and developing thicker, shorter stems.
Wind is an important touch stimulus for many plants. Trees sense the wind and respond by changing their growth form and developing greater mechanical strength. Trees growing in very windy spots are short, with strong, thick trunks, and they often take on a windswept shape. This helps them avoid being blown down in windstorms.
Vines and other climbing plants respond differently to touch: they grow toward the object touching them by altering the growth rate of each side of the stem. For example, if you repeatedly stroke a cucumber tendril on the same side every day, it will bend in the direction of the touch. This behavior helps vines locate and climb structures that can support them.
Does Tickling Plants Help Them Grow Stronger?
Seedlings grown indoors are susceptible to etiolation, or excessively tall and spindly growth, especially when they don’t get enough light. Tickling seedlings grown indoors can help prevent etiolation and strengthen their stems. You can also mimic outdoor wind by placing a fan near your seedlings – this touch stimulus can encourage stronger growth.
Tickling your plants is a fun experiment, but of course, it’s very important to provide indoor plants with what they need to ensure they grow properly. Prevent etiolation by giving your plants enough light, and avoid excessive nitrogen fertilizer, which can encourage weak growth.
Be sure to harden off your plants before transplanting them outdoors. Exposure to outdoor wind conditions will strengthen your plants’ stems and ensure they can tolerate the garden environment after they’re transplanted.
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Touching story: cucumber plant seedlings need a little TLC. Photograph: OksanaRadchenko/Getty Images/iStockphoto
Touching story: cucumber plant seedlings need a little TLC. Photograph: OksanaRadchenko/Getty Images/iStockphoto
Last modified on Tue 19 Jun 2018 12.48 BST
I f you are a gardener, in April your windowsills will probably look just like mine: a jumbled mass of tray after tray of tiny seedlings crammed on to every surface available. As they grow they inevitably become increasingly closely packed, shading each other from the precious little light available at this time of year.
Eventually they will start to grow long and leggy, in a process us botanists call etiolation. These etiolated plants will be weak and floppy, far more likely to fail when eventually transplanted out into the garden. That is if fungal diseases don’t pick them off before they ever get to that stage. A nightmare.
Fortunately, there are two simple tricks that can dramatically reduce etiolation in young seedlings, creating stockier, sturdier plants. The best bit? They don’t involve any special kit, cost or chemicals, just five minutes of your time in total.
As etiolation is caused by lack of light, a really easy way to prevent it is by simply improving the amount of sunlight that gets to your seedlings in the first place. Although even scrupulously clean window glass may filter out up to 20% of the wavelengths used by plants, dusty glass can slash the light getting through by half. A quick wipe (especially on the outside of your windows) could make a significant impact – even if they look pretty clean.
Much of the light that is getting through the glass may additionally be bypassing your little army of seedlings so try to arch them towards the window in search of catching the most rays. A simple reflector can also instantly sort this out by bouncing back the rays on to the leaves.
Aluminium foil is perfect for the job. Wrap a piece of cardboard in the stuff and place it on the interior side of the window or simply line the surface of the windowsill and you will see a noticeable improvement in light levels and more balanced growth as a result.
Finally, here is an even simpler trick that requires just 10 seconds of your time a day. It may sound a little mad, but I promise it is based on sound science. A gentle stroking of the surface of your seedlings mimics the action of wind and passing animals and will trigger vibration sensors in the plants, causing them to respond by growing stockier and stouter to resist damage.
It’s a phenomenon called thigmomorphogenesis (I love a good geekspeak word) and it is used by commercial growers employing large fans or even robots to boost seedling resilience as much as 70%. Fortunately a 10-second tickle each day will work just as well for the average home grower. No, this is not an April fools!
Growing potatoes: New fertilizing tricks will boost spud crop
Think the lowly spud is something you put ketchup on and serve as filler? Think again.
Take a close look at the nutrient-packed powerhouse you can grow in your garden. High in potassium, vitamins C and B6 and iron, potatoes got a bad rap when diet gurus declared them off limits, shunning them as just empty calories.
“Anybody who thinks that is full of beans,” says David Holm, a Colorado State University professor and potato breeder.
“Potatoes are important in fighting diseases, like cancer or glaucoma they’re good for you,” he says.
Potatoes are fun and easy to grow, plus they’re beautiful, said Samuel Essah, an agronomy professor who works with Holm at the CSU San Luis Valley Research Station.
Together, the duo research and try out promising spuds, looking for a few that will make it to the market.
“A lot of people like heirlooms, they like the nostalgia. Others want new stuff they’ve never seen before,” says Verlin Rockey, co-owner with Craig Rockey of the Potato Garden in Austin, a potato purveyor for backyard growers.
“We offer those, plus unusual shapes, colors, and European varieties,” says Verlin. The father-son duo purveys an astonishing 85 types of potatoes, including those with a low glycemic index or a high level of antioxidants.
To ensure success they send out seed potatoes with brochure full of growing instructions. The tips are also available at their website, potatogarden.com.
Here are tips from the three experts on spud success.
Choose variety carefully
Let flavor, color and length of growing season guide your picks. Favorite varieties of Holm, Essah and the Rockeys include Colorado Rose, Desiree, or Sangre red potatoes Nicola or Carola yellow potatoes Purple Majesty or Midnight Moon purple potatoes, and all-around great russets Canela or Sierra russets.
Short-season potatoes are excellent for gardeners at altitude.
“Those mountain gardeners have the advantage of warm days and cool nights,” said Holm. “The potato plant is a factory, taking carbon dioxide and sunlight and converting it to sugar. When temperatures drop at night, it stores it in the tubers, giving them higher-quality solids.” What that means in the frying pan is, such potatoes lose less water, so they’ll take up less oil and have a healthier nutrient profile.
Use seed potatoes
Get good, healthy seed stock, not grocery-store potatoes, for the healthiest plants. Let your seed potatoes sit indoors, in medium light, until they develop stocky sprouts from the eyes. Cut the larger potatoes, leaving at least one eye per two-inch square, and let the cuts skin over for a day before planting. If the seed potato is smaller than an egg, plant it whole.
Plant them now
Mid-April through mid-May is ideal potato-planting time. The soil has warmed above 45 degrees, and you’ve got time for the plants to grow plump tubers.
First, it’s good to know what crop was in that spot last. Legumes such as beans or peas leave behind nitrogen that potatoes love. If these veggies were planted in your potato patch last year, go easy on fertilization. It’s a good idea to get a soil test done to determine how much available nitrogen you have.
Build a ridge of loose soil, approximately 6 inches tall, then push the seed 4 to 5 inches deep into the ridge. Space rows 34 inches apart and space the plants 12 to 14 inches apart. Fingerling potatoes can be closer — 9 to 12 inches apart.
As they grow, you’ll hill them up. Just as the potato sprout noses up from the earth, pull the soil up and over the plant, covering it with 7 to 8 inches of soil for a total of 12 inches above the seed. You only need to do this once.
Care and feeding
With potatoes, you need to stay on top of irrigation, checking plants to be sure they aren’t waterlogged. Smaller types take 12 inches of water per season larger spuds will need 16.
Managing nitrogen is crucial to success with potatoes, Essah says. “Too much and you get a lot of top growth at the expense of tubers.” But he also has a secret that makes feeding potatoes easier: It’s all in the timing.
Using his secret involves calculating how much nitrogen your plants need. Each plant only needs a total of one-fifth ounce total nitrogen for the whole season. Go with granular nitrogen to make it easy to measure. For an organic alternative, try Acton, a product the Rockeys developed to provide all the nutrients and beneficial microbes the potato plant needs to thrive.
Essah’s formula is to mix 60 percent of the total amount of nitrogen the plant needs into the soil of the ridge before the seed potato is planted.
Then, about six to seven weeks later, split the remaining nitrogen into two or three applications, approximately two weeks apart. Feeding your plant more nitrogen, too soon, delays tuber set, which means you get a smaller crop of potatoes to enjoy.
To fine-tune the timing on later feedings, check each plant to ensure that tubers have set and and are sizing up by “tickling” them. Reach into the soil and gently feel around the plant’s roots to see if tubers are growing. You want them to be the size of a cherry or larger.
Practice good weed control. The best way is to pluck out weeds by hand, not with a hoe or other weeder, to avoid damaging the baby potatoes.
Get ready to harvest
Potatoes are pretty plants. But to reap your harvest, you’ve got to kill the vines.
To tell if they’re ready, count the days required to maturity of your potato variety (here’s where keeping good garden records helps, but you can also look the variety up online). Then — because plants don’t read websites or labels, tickle up a plant or two to see if the spuds are the size you want. If you’re the impatient sort, see what your records say for your variety about harvesting “new” potatoes. You can always harvest one plant and leave the rest to continue to get bigger.
Chop off vines 14 to 20 days before you want to dig your potatoes, marking the date you did it on the calendar (you’d be surprised what a gardener can forget during the frenzy of harvest). Potato skins toughen up once vines die, which helps them store longer and stand up to a bit of handling.
Prepping for Success
Preplanning and preparation will help ensure a successful outcome when dividing perennial dianthus for propagation. First, water the plant deeply a day or two before digging it up. Run a garden hose on low at the base of the plant for 10 to 15 minutes or until the soil feels very wet in the top few inches. While the water soaks in, prepare your tools and planting site or pots.
Speed is of the essence when propagating plants such as perennial dianthus from divisions. Prepare a planting site with the same growing conditions as the existing plant, providing at least 12 square inches of space for each division. Alternatively, fill a 1-gallon nursery container half full of moist potting soil for each division you intend to make.
Clean, sharp cutting tools are essential when dividing perennial dianthus because dirty tools can spread bacterial and fungal infections that can cause your divisions to fail. Wipe down the blade of a very sharp gardening knife with rubbing alcohol to sanitize it and be sure to wipe it down between cuts to keep it sanitary.
Potting Up or Planting Leggy Seedlings
Can you bury leggy seedlings deeper in the soil?
Generally, yes, you can plant leggy seedlings deeper in the soil to help compensate for the extra-long stems! However, avoid the temptation to plant them deeper right away, when they’re still very young and tender. Weak, thin, small stems may rot once they’re buried in damp soil. Wait at least several weeks, and after taking steps to strengthen and/or harden off the leggy seedlings as described above.
Once the stems are more tough and strong, you should be able to bury a portion of the leggy seedling stem – either by potting them up, or transplanting them outside. Or, you may do both! For instance, we start our tomatoes in small 4” seedling pots. Then after about a month, we pot up the seedlings into larger 8” nursery pots and bury the stem by a couple inches at that time. Then when we transplant them out into the garden, we can bury the stem a few more inches if needed.
Potting up a leggy tomato seedling from a 4″ nursery pot to an 8″ pot. I put a small amount of soil on the bottom of the new pot, but will otherwise keep the root ball deep in the new container so that I can bury the stem a couple of inches. It looks like I also removed a lower branch or two.
How deep can you plant leggy seedlings?
Well, that depends on the type of plant and size of the seedling! The goal is to bury the leggy seedling stem enough so that the plant isn’t too top heavy and can successfully grow. Otherwise, I personally err on the side of caution and avoid burying them more than necessary.
- Most common garden vegetables don’t mind if you bury their stem part way or all the way up to theirfirst set of true leaves (or first set of lateral branches). You can do this with peppers and members of the brassica family: kale, collard greens, broccoli, Brussels sprouts, or cauliflower.
If the vegetable is one that should normally form a head or bulb right at the soil line, then you’ll want to bury it up to that point – where the stem branches and begins to form the main crop, so that its weight will be supported on the soil surface. Consider a head of lettuce, bok choy, cabbage, or kohlrabi for example.
You can plant some seedlings even deeper. Tomatoes and tomatillos are prime examples. Due to their advantageous root systems, it is a common practice to remove the lowest few branches and bury leggy tomato seedlings up past that point (planting up to half of the plant underground). Tomatoes and tomatillos will grow new roots off of the buried portion of the stem! More roots equals a more robust and healthy plant.
It is less necessary to deeply bury seedlings of plants that will continue to grow tall branching stems well above the soil line anyways, such as flowers or herbs.
Planting a slightly leggy cauliflower seedling, burying the stem a couple inches (up to the first set of leaves).
This was a tomatillo seedling that got WAY too tall in our greenhouse. It had ample light, but we started it too soon (I forgot how quickly tomatillos get large!) so I buried the stem a good 6 inches deep when transplanting it into the garden. I still ended up starting a new seedling to replace it because I didn’t like it’s growth structure, so I dug it up about a month later to replace it. All of these new roots grew off the buried portion of the stem in that short time! Tomatoes do something similar, but not quite as vigorously.
And that concludes this lesson on leggy seedlings.
All in all, do not feel bad if your seedlings are a little leggy! Even the most experienced gardeners doing all the “right” things grow some slightly leggy seedlings sometimes – ourselves included. As you saw in this article, all hope is not lost! There are a number of ways to prevent and fix leggy seedlings. Plus, you’ll learn from your mistakes and improve next season. That is one thing I love about gardening: there is always something new to learn, and there is always next year.
Please let me know if you have any questions in the comments below. Also, please pin or share this article if you found it valuable! Cheers to growing happy seedlings!