---
title: "What Seeds Should Not Be Used for Microgreens"
description: "Wondering what seeds should not be used for microgreens? Nightshades, raw kidney beans, treated seed, buckwheat, alfalfa and borage, each with its reason."
url: "https://microgreensguru.com/blog/seeds-not-to-grow-as-microgreens/"
lang: "en"
published: "2026-10-15"
modified: "2026-11-09"
author: "Cal Hewitt"
image: "https://microgreensguru.com/og/blog-seeds-not-to-grow-as-microgreens.jpg"
alternates:
  es: "https://microgreensguru.com/es/blog/semillas-no-usar-microgreens.md"
---

# What Seeds Should Not Be Used for Microgreens

[Cal Hewitt](https://microgreensguru.com/about/cal-hewitt/) Published October 15, 2026 Checked November 9, 2026

- growing
- seeds
- food safety

![Potting bench with a blank paper seed packet leaning against a clay pot beside a tray of young tomato seedlings showing first true leaves](https://microgreensguru.com/images/blog/seeds-not-to-grow-as-microgreens.jpg)

Nightshade shoots, raw legume shoots such as kidney beans, three named crops (buckwheat, alfalfa and borage) and treated seed are the four groups to check before you sow anything.

Each group has a different reason behind it, and each has a different action for you to take with the packet in your hand. Some you leave out of the tray entirely. For others you read the label, or check the crop entry first.

If you already have a tray sown, the same checks apply. Find the packet, match it to the group below, and decide before the tray goes any further.

## Nightshade seeds: tomato, potato, eggplant, pepper, tomatillo and ground cherry

Leave these out of the tray. The nightshade family (Solanaceae) is the first group to check, and the reason comes down to plant stage. Edible mature fruit does not make the seedling or the foliage edible. You eat a ripe tomato or a roasted eggplant, but the shoots and young leaves of those plants are a different part of the plant with different chemistry. [NC State University Extension](https://stem.plantsforhumanhealth.ncsu.edu/school-gardens/microgreens/) defines microgreens as seedlings harvested at about 1 to 3 inches tall, and it specifically excludes tomato, eggplant, pepper and potato shoots because the nightshade family can be toxic.

![Sunny raised vegetable bed with staked tomato plants carrying green fruit and a row of pepper plants beside them over mulched soil](https://microgreensguru.com/images/blog/seeds-not-to-grow-as-microgreens/staked-tomato-and-pepper-plants-in-a-sunny-garden-bed.jpg)

Here is each plant with its compound and the part of the plant the source describes:

- **Tomato.** The green tissues, including leaves, stems and unripe fruit, contain the glycoalkaloids alpha-tomatine and dehydrotomatine. [Health Canada](https://www.canada.ca/en/health-canada/services/food-nutrition/reports-publications/food-safety/glycoalkaloids-foods.html) identifies those green parts as unsuitable to eat, and [University of Wisconsin Extension](https://hort.extension.wisc.edu/files/2014/11/A3687.pdf) names tomatine in the foliage.
- **Potato.** Leaves, flowers, eyes, green skin and sprouts carry alpha-solanine and alpha-chaconine. [Poison Control](https://www.poison.org/articles/are-green-potatoes-safe-to-eat-191) reports gastrointestinal and neurological toxicity. A potato microgreen includes the shoot and young leaves, so do not eat it.
- **Eggplant.** [NC State's Plant Toolbox](https://plants.ces.ncsu.edu/plants/solanum-melongena/common-name/eggplant/) lists the flowers, leaves, stems and roots as toxic.
- **Pepper.** [Ask Extension](https://ask.extension.org/kb/faq.php?id=333029) says solanaceous plants carry high concentrations of alkaloids and that their leaves should not be eaten. Capsaicin is what makes the fruit hot, but it is not the basis for treating a pepper seedling as safe food.
- **Tomatillo and ground cherry.** Both are nightshade family plants, so keep them out of the tray too.

These findings concern the plants' green tissues, and the guidance is not to eat them. The guidance for these plants is not to eat the green tissues, so keep the seed out of the tray. The packet is for the garden bed, not the microgreen tray.

Today's action: if a packet says tomato, potato, eggplant, pepper, tomatillo or ground cherry, set it aside for the garden.

## Raw legume shoots, including kidney beans

Kidney beans and several other legumes should not be eaten as raw shoots or raw microgreens. The compound is phytohaemagglutinin, also spelled phytohemagglutinin and shortened to PHA. It is a lectin, a plant protein, concentrated in raw beans.

![Large clear glass bowl of dark red kidney beans covered in water on a kitchen counter, a few beans swollen, with a wooden spoon beside it](https://microgreensguru.com/images/blog/seeds-not-to-grow-as-microgreens/dry-red-kidney-beans-soaking-in-a-glass-bowl-of-water.jpg)

The FDA's [Bad Bug Book entry on phytohaemagglutinin](https://www.fda.gov/media/83271/download) puts numbers on it. Raw kidney beans measure 20,000 to 70,000 hemagglutinating units. Fully cooked kidney beans measure 200 to 400. White kidney beans carry about one-third the level of red kidney beans, and broad (fava) beans carry about 5% to 10% of the red kidney bean level. The FDA's page on [natural toxins in food](https://www.fda.gov/food/chemical-contaminants-pesticides/natural-toxins-food) reports nausea, severe vomiting and diarrhea at high levels from raw or undercooked beans, and says adequate cooking destroys PHA. Boiling for at least 30 minutes is the FDA's recommendation.

Those figures come from the beans themselves, so read them as a measure of how concentrated the lectin is in the seed. The point for your tray is that soaking alone, sprouting or low-temperature cooking should not be treated as making a kidney bean shoot safe to eat raw. The caution is strongest for red kidney beans, but PHA occurs in many bean species, and the FDA lists kidney beans, green beans and fava beans as examples. [Health Canada's page on lectins in dry legumes](https://www.canada.ca/en/health-canada/services/food-nutrition/food-safety/chemical-contaminants/natural-toxins/lectins-legumes.html) covers the same family of compounds. For soybean, lima bean and other legumes you might be tempted to sprout, do not assume the raw shoot is safe to eat.

Today's action: if the packet is a dry bean meant for the soup pot, leave it out of the tray, and cook beans the way the FDA describes.

## Buckwheat, alfalfa and borage

Three crops sell as microgreen seed and carry a caution of their own. Each gets one line here and a link to its crop entry, where you can check the details before sowing.

![Three small shallow black trays in a row on a table holding buckwheat seedlings, fine thread like alfalfa sprouts and fuzzy leaved borage seedlings](https://microgreensguru.com/images/blog/seeds-not-to-grow-as-microgreens/three-shallow-trays-of-buckwheat-alfalfa-and-borage-seedlings.jpg)

**Buckwheat** carries fagopyrins, photosensitive compounds associated with fagopyrism, a phototoxic reaction that follows exposure to light. Published reviews, including one on [the nutritional and bioactive characteristics of buckwheat](https://pmc.ncbi.nlm.nih.gov/articles/PMC10171551/), describe fagopyrin as a toxic photoreactive compound found mainly in green tissues such as leaves and flowers. That makes the green parts of the plant a different food from cooked buckwheat grain, so treat buckwheat microgreens as a caution crop: avoid large raw servings, especially before you go out into the sun. Read the [buckwheat entry](https://microgreensguru.com/microgreen-types/buckwheat/) before you sow.

**Alfalfa** carries L-canavanine, a non-protein amino acid that resembles arginine. A peer-reviewed study of [the natural abundance of L-canavanine in alfalfa](https://pubmed.ncbi.nlm.nih.gov/21214431/) measured it at 1.3% to 2.4% of dry matter in commercial alfalfa sprouts and 1.4% to 1.8% in the seeds it tested. That study looked at sprouts and seeds, so it does not give a safe dose for alfalfa microgreens. Alfalfa also carries the ordinary raw-sprout risk of microbial contamination, so handle it with the care raw sprouts need. Do not treat it as an unlimited raw salad green, and look at the [alfalfa entry](https://microgreensguru.com/microgreen-types/alfalfa/) first.

**Borage** carries unsaturated pyrrolizidine alkaloids, including amabiline, supinine, lycopsamine, intermedine, acetyllycopsamine and acetylintermedine. [Memorial Sloan Kettering Cancer Center](https://www.mskcc.org/cancer-care/integrative-medicine/herbs/borage) identifies these compounds as hepatotoxic, and its page covers borage plant material, including the leaves and other aerial parts. Do not use borage as a routine edible microgreen. The [borage entry](https://microgreensguru.com/microgreen-types/borage/) has the crop details.

Rhubarb belongs in this same mental pile even though few people think of sowing it as a microgreen. Its leaves contain high levels of oxalic acid and soluble oxalate salts, and [University of Minnesota Extension](https://extension.umn.edu/garden-and-home/yard-and-garden/gardening-in-minnesota/growing-rhubarb) and [Oregon State University Extension](https://extension.oregonstate.edu/catalog/pub/ec797?reference=catalog) treat only the mature leaf stalk as edible.

Today's action: for buckwheat, alfalfa or borage, open the crop entry before you sow, and read what it says about serving and handling.

## Treated seed: read the dye and the label

Treated seed is coated with a pesticide, such as a fungicide or an insecticide, and then dyed. The dye is the warning. The [National Pesticide Information Center](https://npic.orst.edu/ingred/ptype/treated-seed.html) says treated seed is commonly coated in a brightly colored dust, mist or clay, that the unnatural color is there to signal the treatment, and that treated seed must never be eaten or used as animal feed. The EPA's rule for seed-treatment products, [40 CFR 153.155](https://www.law.cornell.edu/cfr/text/40/153.155), generally requires an approved dye that gives the seed an unnatural color, with listed exceptions.

![Two small white dishes side by side on a counter, one holding bright pink dyed seed and the other plain tan seed of the same kind, with a small spoon between them](https://microgreensguru.com/images/blog/seeds-not-to-grow-as-microgreens/pink-dyed-seed-in-a-dish-beside-plain-seed.jpg)

The label tells you the rest. Under the Federal Seed Act, as the [USDA Agricultural Marketing Service explains](https://www.ams.usda.gov/sites/default/files/media/LabelingRequirementsforChemicallyTreatedSeed.pdf), the label has to name the treatment, for example "Treated with Thiram" or "Thiram Treated." If the chemical left on the seed is harmful to people or vertebrate animals, the regulation requires one of these statements: "Do not use for food," "Do not use for feed," "Do not use for oil purposes," or "Do not use for food, feed, or oil purposes." Seed treated with a mercurial or similarly toxic substance must carry a skull-and-crossbones symbol and the word "Poison" in red letters. The EPA's [Label Review Manual](https://www.epa.gov/sites/default/files/2015-08/documents/lrm-chap1-18-aug-2015.pdf) carries the same food, feed and oil wording.

Microgreens are food, so the wording "Do not use for food, feed, or oil purposes" disqualifies the seed. It does so whether the color has faded or the seedling looks healthy. A clean-looking tray from treated seed is still a tray from treated seed.

Today's action: turn the packet over, look for a treatment name and a "Do not use for food" line, and if either is there, do not sow it for eating. [Seed that is untreated and bought for eating](https://microgreensguru.com/blog/best-microgreen-seeds-for-beginners/) is the better starting point, and the guide to [buying microgreen seed](https://microgreensguru.com/grow-microgreens/buying-microgreen-seed/) walks through what to look for on the packet.

## What about ordinary garden seed?

Garden seed is not automatically off the list, and "microgreen seed" is not a guarantee by itself. The deciding checks are the plant's identity and the treatment status. Ordinary garden seed can generally go in a tray when:

- The plant is edible at the seedling stage.
- The seed is untreated and has no pesticide coating.
- The packet does not say "treated," name a fungicide or insecticide, or carry a food or feed prohibition.
- You know what the seed is, and it has not been mixed with excluded species.

Extension guidance supports this. Penn State Extension says seed not sold specifically for microgreens can be used when it is organic or untreated, Clemson Extension recommends seed labeled for microgreens or marked untreated, and [University of Vermont Extension](https://www.uvm.edu/extension/news/brighten-winter-microgreens) says untreated seed works and organic is preferred. Colorado State Extension and South Dakota State Extension both point to untreated seed as well. If you want the longer comparison, the post on [microgreen seeds versus regular seeds](https://microgreensguru.com/blog/microgreen-seeds-vs-regular-seeds/) covers it.

Organic labeling helps because certified organic seed is not treated with prohibited synthetic pesticides, but read the packet anyway.

## Hold the packet up against the four groups

Run through these in order, with the packet in your hand:

1.  **Does the name say tomato, potato, eggplant, pepper, tomatillo or ground cherry?** Leave it out.
2.  **Is it a raw bean, such as a kidney bean?** Leave it out.
3.  **Is it buckwheat, alfalfa or borage?** Check the crop entry before sowing.
4.  **Is the seed brightly dyed, or does the label name a treatment or say "Do not use for food"?** Do not sow it for eating.

If none of those apply, you have a seed that is untreated and identified, and the next question is whether the crop itself is a good microgreen, which the crop entries answer one at a time.

## Frequently asked questions

**Can I eat the microgreens if the seed was treated but I rinse them well?** The Federal Seed Act wording says the seed is not to be used for food, feed or oil purposes, and the National Pesticide Information Center says treated seed must never be eaten. Rinsing does not change what the label says, so keep treated seed for planting in the ground, not in a tray for eating.

**Do tomato or pepper seeds need to be dyed to be a problem?** No. The nightshade concern is about the plant's shoots and young leaves, not about the seed coat or a dye. Plain, untreated tomato or pepper seed still gives you a seedling you should not eat.

**Does cooking make nightshade shoots or buckwheat greens safe?** Cooking is the fix for raw kidney beans, because the FDA says adequate cooking destroys PHA. For nightshade shoots and buckwheat greens, the guidance concerns the plant material itself, so do not rely on cooking; keep both out of the microgreen routine.

**What should I do with a tray I already sowed from a seed on this list?** Do not harvest it for eating. Check the packet against the four groups above, and if it falls in one, dispose of the tray and start again with a seed you have identified and checked.

## Before you sow

Most of what goes wrong here is solved by looking at the packet for thirty seconds. Identify the plant, look for a treatment name and a food prohibition, and open the crop entry if it is buckwheat, alfalfa or borage. Write the seed's name and source on the tray label so you can trace it later.

## Sources

Prices, stock and specifications are as the linked pages showed them on 2026-11-09.

- [NC State University Extension](https://stem.plantsforhumanhealth.ncsu.edu/school-gardens/microgreens/)
- [Health Canada](https://www.canada.ca/en/health-canada/services/food-nutrition/reports-publications/food-safety/glycoalkaloids-foods.html)
- [University of Wisconsin Extension](https://hort.extension.wisc.edu/files/2014/11/A3687.pdf)
- [Poison Control](https://www.poison.org/articles/are-green-potatoes-safe-to-eat-191)
- [NC State's Plant Toolbox](https://plants.ces.ncsu.edu/plants/solanum-melongena/common-name/eggplant/)
- [Ask Extension](https://ask.extension.org/kb/faq.php?id=333029)
- [Bad Bug Book entry on phytohaemagglutinin](https://www.fda.gov/media/83271/download)
- [natural toxins in food](https://www.fda.gov/food/chemical-contaminants-pesticides/natural-toxins-food)
- [Health Canada's page on lectins in dry legumes](https://www.canada.ca/en/health-canada/services/food-nutrition/food-safety/chemical-contaminants/natural-toxins/lectins-legumes.html)
- [the nutritional and bioactive characteristics of buckwheat](https://pmc.ncbi.nlm.nih.gov/articles/PMC10171551/)
- [the natural abundance of L-canavanine in alfalfa](https://pubmed.ncbi.nlm.nih.gov/21214431/)
- [Memorial Sloan Kettering Cancer Center](https://www.mskcc.org/cancer-care/integrative-medicine/herbs/borage)
- [University of Minnesota Extension](https://extension.umn.edu/garden-and-home/yard-and-garden/gardening-in-minnesota/growing-rhubarb)
- [Oregon State University Extension](https://extension.oregonstate.edu/catalog/pub/ec797?reference=catalog)
- [National Pesticide Information Center](https://npic.orst.edu/ingred/ptype/treated-seed.html)
- [40 CFR 153.155](https://www.law.cornell.edu/cfr/text/40/153.155)
- [USDA Agricultural Marketing Service explains](https://www.ams.usda.gov/sites/default/files/media/LabelingRequirementsforChemicallyTreatedSeed.pdf)
- [Label Review Manual](https://www.epa.gov/sites/default/files/2015-08/documents/lrm-chap1-18-aug-2015.pdf)
- [University of Vermont Extension](https://www.uvm.edu/extension/news/brighten-winter-microgreens)

## Keep reading

- The journal

    ### Best Microgreen Seeds for Beginners: Which Crops to Order First

    Compare the best microgreen seeds for beginners by seed per tray and harvest days. Radish, broccoli, kale and arugula need no soaking; pea and sunflower do.

    [Read Best Microgreen Seeds for Beginners: Which Crops to Order First](https://microgreensguru.com/blog/best-microgreen-seeds-for-beginners/)
- The journal

    ### Using your own seeds in a LetPot: sponges, seed count and light

    Using your own seeds in a LetPot instead of pods? See the seed count per sponge, the light height for germination, and the failures owners have reported.

    [Read Using your own seeds in a LetPot: sponges, seed count and light](https://microgreensguru.com/blog/use-your-own-seeds-in-a-letpot/)
- The journal

    ### How to Grow Sprouts at Home: Steps, Timing and Safety

    Follow the full jar method for how to grow sprouts at home, with soak and rinse timing, harvest day, storage rules, and who should avoid eating them raw.

    [Read How to Grow Sprouts at Home: Steps, Timing and Safety](https://microgreensguru.com/blog/how-to-grow-sprouts-at-home/)
- The journal

    ### Is Homegrown Safer? What the Produce Recalls Actually Change

    Partly, and not for the reason people think. Growing your own does not remove contamination risk, it moves it onto seed, substrate and water, which are three things you can act on. And one tray is one to two days of one adult's vegetables, not a replacement.

    [Read Is Homegrown Safer? What the Produce Recalls Actually Change](https://microgreensguru.com/blog/produce-recalls-and-growing-your-own/)