Hot Water Seed Treatment: Should I Treat My Seeds With Hot Water
By: Tonya Barnett, (Author of FRESHCUTKY)
Proper garden maintenance and sanitation practices areparamount in the garden. Unfortunately, many diseases that occur are often theresult of factors beyond the control of home gardeners, such as in the case ofseed-borne diseases, where infection may be especially frustrating to growers.There are, however, some steps that can be taken to help prevent thecontamination of certain diseases in crops.
Many forms of blight, leaf spot, and mildew occur throughthe planting of contaminated seed. This is especially true of crops like tomatoes,peppers,and various brassicas. In recent years, many growers have turned to the processof hot water seed treatment as a means of prevention for these crop diseases.
Should I Treat My Seed with Hot Water?
Many organic and conventional gardeners may be left to ask,“Why soak seeds in hot water?” As it stands, hot water treatment of seedsallows water to pass into the seed and kill possible seed-borne pathogens. Whenthe process of hot water seed soaking occurs, the seeds are able to be plantedinto the garden without the risk of the pathogens building in the soil andinfecting plants.
The decision to treat seeds with hot water varies greatly.While many types of seeds do benefit from soaking in hot water, others maysuffer from the process. For example, large seeds like cornand pumpkinsshould not be soaked, as the process will damage and drastically reducegermination of the seed.
The process of treating seeds with hot water will alsorequire knowledge, as well as the proper equipment to ensure success. Differentvarieties of seed will require varying temperatures and varying time periods inwhich the seeds are soaked. Soaking seeds for too long or at incorrecttemperatures will damage the seeds, rather than help create a healthy growthclimate.
While buying the necessary tools to properly treat seedswith hot water may be somewhat expensive, many large scale organic farmers findthe investment worthwhile. Hot water treatment may not be a viable option for allhome gardeners, but many seed suppliers now offer hot water treated seeds forpurchase online.
This article was last updated on
Seed Scarification: How, When and Why to Scarify SeedsSteph Coelho
Steph is a certified Square Food Gardening Instructor who has been gardening for more than 10 years in Canada where the winters are long and cold, and the summers are unpredictable. She is a volunteer for her community's Incredible Edible project. In the past she created an educational gardening space for seniors and taught classes at a local community center where she created her own curriculum and activities. She participated in several local municipal garden days where she set up a booth to educate citizens about the joy of gardening.
Have you ever read on a packet that a seed needs scarification before planting? While it’s not a common instruction, it’s a handy trick to know because it speeds up and improves germination rates.
So what in the world is scarification?
Seed scarification involves weakening the coating of a seed to encourage sprouting. This can be done in a number of ways, but most common is mechanically breaking a seed’s shell.
So when do you need it and how do you make it happen? Here’s what to know.
Some plant pathogens, including specific fungal, oomycete, and viral pathogens, can be carried on seed some can only infest the seed surface, but others are able to penetrate the seed coat and survive within the seed. In both cases, the pathogen can then grow with the seed when it is planted, resulting in an infected plant. Therefore, starting with disease-free seed is an important step towards growing disease-free crops. Seeds can be treated with chlorine or pesticides to eliminate pathogens that are associated with the surface of seeds. However, these treatments cannot penetrate the seed coat, and therefore leave internal pathogens untouched. Hot water can penetrate the seed coat and can also kill pathogens, making it a useful tool for managing seed-borne pathogens.
Treating your seeds with hot water can help prevent the establishment of seed-borne diseases on your farm, or prevent their reintroduction year after year. However, it’s important to note that while hot water seed treatment will kill pathogens on and within your seeds, it does not protect crops from disease and does not guarantee disease-free crops. Crop rotation and field sanitation are key for preventing diseases that overwinter on crop debris, and crops need to be scouted regularly for wind-, water-, and insect-borne diseases.
Hot water seed treatment has the beneficial effect of priming seeds, resulting in faster germination than untreated seed. However, the treatment can decrease germination rates, especially of older seed (more than 1 year old) or seeds that were grown under stressful environmental conditions. Treated seed does not remain viable for as long as untreated seed and should be planted during the growing season immediately following treatment.
Deciding which seeds to treat
To decide whether to use hot water treatment, first determine the likelihood that seed-borne pathogens could be present based on the crop (see Table 1 for reference). Tomato, pepper, and brassicas are good candidates for hot water seed treatment because there are common bacterial and fungal diseases of these small-seeded crops that can be easily killed through treatment. Next, ask your seed supplier if the seed was produced in a way to minimize exposure to seed-borne pathogens and if the seed was tested for their presence. Find out if the seed has already been treated with hot water or if it has been primed (pre-soaked to promote earlier and more uniform germination), as treating again could adversely affect the seed. You should also not treat seed that has a fungicide or insecticide treatment coating, as it will wash off during treatment. Only a few companies routinely hot-water treat seeds—many are reluctant because there is a risk that germination rate will drop if the water is too hot or if the seeds were already exposed to stressful environmental conditions.
Large-seeded crops (beans, cucurbits, peas, corn etc.) are usually not effectively disinfested with hot water treatment because the temperature required to heat the whole seed would kill the outer seed tissue and the seed will not germinate. In some cases, hot water has been used to disinfect just the surface of larger seeds, for example, treating anthracnose on beans.
Alternaria leaf spot, Bacterial leaf spot, Black leg, Black rot
Phoma/Canker, Downy Mildew, Cercospora leaf spot
Alternaria leaf blight, Bacterial leaf blight, Cercospora leaf spot, Crater rot/foliar blight
Bacterial leaf spot, Cercospora leaf spot, Septoria leaf spot, Phoma crown and root rot
Anthracnose, Early blight, Phomopsis, Verticillium wilt
Anthracnose, Bacterial leaf spot, Lettuce mosaic virus, Septoria leaf spot, Verticillium wilt
Purple blotch, Stemphylium leaf blight, Basal Rot, Botrytis blight, Smudge, Black mold
Anthracnose, Bacterial leaf spot, Cucumber mosaic virus, Pepper mild mosaic virus, Tobacco mosaic virus, Tomato mosaic virus
Bacterial leaf blight, Alternaria leaf blight, Black rot, Cercosporoid leaf blight, Septoria blight
Anthracnose, Cladosporium leaf spot, Cucumber mosaic virus, Downy mildew, Fusarium wilt, Stemphylium leaf spot,Verticillium wilt
Alfalfa mosaic virus, Anthracnose, Bacterial canker, Bacterial speck, Bacterial spot, Cucumber mosaic virus, Early blight, Fusarium wilt, Leaf mold, Septoria leaf spot, Tomato mosaic virus, Verticillium wilt, Double virus streak
How to Help Pepper Plants Germinate
Peppers, available in a variety of shapes and colors, add a zesty, earthy flavor to meals. Aside from their culinary uses, many peppers make attractive ornamental plants. Pepper seeds need very warm temperatures to germinate, grow and set fruit. The seeds may also take a long time to germinate. For example, some hot pepper varieties, such as "Bhut Jolokia" and "Tepin," take one month or more to sprout. Providing high-quality soil, warmth and nonchlorinated water speeds up this process and results in a higher germination rate.
Mix 1 tablespoon of bloom-boosting flower food with 1 gallon of distilled, nonchlorinated water.
Lay the pepper seeds in a bowl. Cover the seeds with hydrogen peroxide and allow them to soak for one minute. Put the seeds in a fine-mesh strainer or sieve to drain off the peroxide. This treatment kills mold spores.
Fill a seed-starting tray with potting soil. Sprinkle the diluted flower food solution on the surface of the soil.
Plant pepper seeds 1/2 inch apart and 1/8 inch deep. Water the seeds with the diluted flower food solution.
Punch a hole in a clear plastic sheet or lid. Cover the seed-starting tray with the lid. Remove the lid for a few hours each day.
Place the seed-starting tray on a heating mat. Keep temperatures between 80 and 85 degrees Fahrenheit in the daytime and 60 and 70 degrees Fahrenheit at night.
Fill a shallow bowl halfway with the diluted flower food solution. Set the tray in the bowl and allow the soil to soak up the solution. Alternatively, water the seeds with the solution using a spray bottle or watering can.
Watch for germination. Germination times vary depending on the pepper variety. Sweet peppers germinate in six to eight days. Hot peppers take at least 15 days to germinate.
- When seedlings appear, remove the lid from the tray. Hang grow lights about two to four inches above the tray. Leave the lights on for 12 to 16 hours a day. Set pepper plants out in the garden when they are 4 to 5 inches tall. Give each plant 1/2 tablespoon of nitrogen fertilizer when peppers start to appear.
- Do not plant pepper seeds in peat pots or potting soil consisting of mostly peat. Peat may inhibit germination.
Melissa King began writing in 2001. She spent three years writing for her local newspaper, "The Colt," writing editorials, news stories, product reviews and entertainment pieces. She is also the owner and operator of Howbert Freelance Writing. King holds an Associate of Arts in communications from Tarrant County College.