What Are Treated Seeds?

Written By Lara Wadsworth

At True Leaf Market you may notice some seeds are labeled as “Treated” in their titles. This means that it has been coated in a light fungicide. The purpose of this is to reduce seed rot in wet or cool soils. Very few of the seeds we sell are treated, and if a seed is treated, it will be clearly labeled in the title. If you’re buying from True Leaf Market, you will never need to wonder if the seed is treated with something or not. If it does not say “treated,” it is a pure seed and has not been coated with any sort of chemical.

Why Would I Want Treated Seeds For My Garden?

Treated seeds can be a fantastic tool for gardeners who struggle with wet, cool soils. These conditions often prompt damping off diseases such as Pythium, Rhizoctonia, and Fusarium. Treated seeds also prevent seed rot and other early-stage root infections. Treated seeds often show higher and more consistent germination rates. The early protection that treated seeds provide allows seedlings to establish more quickly and vigorously, improving their chances of surviving stressful conditions throughout their life.

All of these benefits culminate in allowing gardeners to plant earlier in the season than otherwise possible. Treated seeds can handle cooler soils better, giving you a head start on the growing season. Therefore, they are ideal for regions with short growing seasons or wet or rainy planting-season weather. Lastly, if you use treated seeds, you may reduce the need for additional fungicide applications during early growth stages, saving time, labor, and cost. Therefore, it is often seen as a better alternative to multiple chemical sprays while still protecting plants

When to choose treated seeds:

• You’re planting in cool, damp soil prone to fungal diseases.
• You’ve faced early disease issues in your garden in previous seasons.
• You want higher germination success and faster early growth.
• You’re looking to reduce early-season interventions like spraying.

What Seeds Are Typically Treated?

True Leaf Market offers treated seeds for seed varieties that are most typically reported to suffer from low germination and seedling failure due to fungal diseases. These include peas, corn, beans, squash, and other common vegetable seeds. These are also typically plants that do best when directly planted (as opposed to started indoors ahead of time) and, therefore, are subject to the whims of nature and weather when yourng.

What Fungicides Are Used For Treated Seeds?

The exact fungicide differs from seed to seed and even between individual varieties. Some examples of common fungicides used on treated seeds sold by True Leaf Market include Mefenoxam (Metalaxyl-M), Captan, Carboxin, Difenoconazole, Thiram, Sedaxane, or Safecoat. All of the chemicals we use are fungicides or low-toxicity alternatives, not insecticides.

Do Treated Seeds Contain Neonics?

Neonics are never included in the coating of treated seeds from True Leaf Market. Neonicotinoids are insecticides that can sometimes be paired with fungicides and are known to do their magic in the internal system of a plant. While this can be an advantage, they are best to avoid with flowers specifically (which almost all plants have). Neonics have been linked to declines in bee populations and other pollinators due to their persistence and potential to contaminate pollen and nectar. Birds that consume seeds treated with neonics may experience toxicity or population declines due to reduced insect prey. Therefore, you can be assured that all of our treated seeds are neonic-free! Some companies may use them, especially when treating vegetable seeds. So, be sure to do your research before you buy. Transparency is the best policy.

Are Treated Seeds Toxic to Soil Microbes?

Treated seeds that are free of neonicotinoids may still impact soil microbes and overall soil health, depending on the specific fungicides, insecticides, or other chemicals used in the treatment. One unfortunate consideration is that most fungicides cannot differentiate between good and bad fungi. Repeated use may reduce populations of beneficial soil fungi, altering nutrient cycling and organic matter decomposition. Therefore, it is essential to use these tools sparingly if soil health is a concern. You can also combat any potential adverse effects through crop rotation and frequent use of healthy compost in the garden. Unfortunately, treated seeds are not compatible with organic gardening methods, and it is best to seek out other ways to avoid bad fungus when you are aiming for a fully organic garden.

What Is The Difference Between Coated and Treated Seeds?

The most significant difference between coated and treated seeds is that coated (pelleted seeds) are covered with inert materials, while treated seeds are coated with fungicides. Treated seeds are best for gardeners who struggle with early-season fungal issues such as damping off. However, they are not compatible with organic gardening practices. Pelleted seeds are not coated with any chemical. Instead, they are covered with biodegradable clay to make the sowing process easier. This clay is often colored to make small seeds easier to see when planting. Coated/pelleted seeds can also make odd-shaped seeds more manageable to run through a machine for planting.

How Do I Store Treated Seeds?

Proper seed storage is essential to protecting children and pets and ensuring the efficacy of your seeds. Store seeds in their original, labeled packaging to keep important information about the treatment and handling instructions. If the original packaging is damaged, use sealed, airtight containers made of plastic, metal, or glass to prevent exposure to moisture and pests. Ensure the container is clearly labeled with the seed type, the fungicide, and any safety warnings. Store the seeds in a cool, dark, elevated, dry environment away from children, pets, and livestock access. For prolonged storage, add moisture-absorbing packets (e.g., silica gel) to containers to keep seeds dry. Store treated seeds away from untreated seeds to prevent accidental mixing. Do not store treated seeds near food, animal feed, or kitchen supplies to avoid cross-contamination.

In addition to being clearly identified on the packaging, seed treatments are also applied with a brightly colored dye. This is usually a food coloring dye. While the dye itself is harmless and will quickly wash away, it can make treated seeds attractive to children as they can appear like candy. Always keep treated seeds out of reach of children! If a child or animal consumes treated seed, we recommend contacting your poison control center at 800-222-1222 for quick and accurate instructions.

Other Best Practices For Treated Seeds

When handling treated seeds, wear gloves and a mask to avoid skin contact and dust inhalation. While the type and amount of fungicide used to coat our treated seeds are considered very low toxicity to humans, it is always better to be safe than sorry. After handling, wash your hands with soap and water. Treated seeds typically remain viable for 1-2 years, but efficacy decreases over time. Never compost treated seeds, as chemicals may contaminate soil or harm beneficial organisms.

Lara Wadsworth, True Leaf Market Writer

I am a native of Southwestern Michigan, where I also reside, and I love all things plants! I got a Bachelor's Degree in Horticulture and found the first work-from-home job I could get. Now, I spend my days writing for TLM, playing with my dog, eating delicious food with my husband, and plotting my next landscape or gardening move. I believe everyone should get down and dirty in the soil now and then. Happy Gardening!