Which microgreens are not edible? A guide to toxic seedlings

Over 40% of microgreen varieties belong to the Brassicaceae (cabbage) family, known for their edible and nutritious seedlings. However, not all seedlings are safe to eat, and knowing which microgreens are not edible is crucial for home growers and consumers to prevent accidental poisoning. This guide provides the essential information needed to identify and avoid potentially dangerous microgreens.

Quick Summary

Certain plants contain toxic compounds that make their seedling stage inedible. Key examples include the nightshade family, ornamental plants like foxglove, and the leaves of rhubarb, which can contain harmful alkaloids and cardiac glycosides even in their immature form.

Key Points

• Nightshade family microgreens are toxic: Avoid growing microgreens from tomato, potato, eggplant, and pepper seeds, as they contain harmful alkaloids like solanine and tomatine.

• Ornamental plants can be fatal: Never consume microgreens from ornamental or wild plants like foxglove or castor bean, as they contain lethal toxins.

• Rhubarb leaves are poisonous: Only the stalks of rhubarb are edible; the leaves and microgreen versions are toxic due to high levels of oxalic acid.

• Use untreated, food-grade seeds: Always purchase seeds specifically marketed for microgreens or sprouts to ensure they are free of harmful chemical coatings and pesticides.

• Practice good hygiene: Prevent bacterial contamination by ensuring your seeds are clean, using sterile growing medium, and washing your microgreens properly before consumption.

• When in doubt, throw it out: If you are uncertain about a plant's edibility, do not risk it. Stick to known safe varieties to protect your health.

Understanding Microgreen Safety: What to Avoid

Microgreens have become a popular addition to a healthy diet, celebrated for their concentrated nutritional content and intense flavors. While many varieties, such as broccoli, radish, and sunflower, are perfectly safe and beneficial, the misconception that all young plants are edible can lead to serious health risks. The danger lies in plants that contain toxins at their early growth stages, even if the mature plant or its fruit is safe to eat. Knowing these exceptions is the first step toward safe microgreen consumption.

The Deadly Nightshade Family

The Solanaceae, or nightshade family, is a well-known group of plants that includes many common food items like tomatoes, potatoes, eggplants, and peppers. While the mature fruits of these plants are staple ingredients, their leaves and stems, particularly at the microgreen stage, contain toxic alkaloids.

• Potatoes: Potato sprouts and leaves contain high levels of the glycoalkaloid solanine, which is highly toxic.
• Tomatoes: Tomato seedlings contain tomatine, an alkaloid that can cause digestive and neurological distress.
• Eggplants: Similar to other nightshades, eggplant seedlings possess toxic alkaloids.
• Peppers: All peppers, including bell peppers and chili peppers, are part of this family and should not be grown as microgreens.

Ornamental and Wild Plants

Some beautiful ornamental plants contain powerful toxins that are present throughout their lifecycle, including the seedling phase. Unless you are an expert botanist, it is best to avoid growing any wild seeds or ornamental plants as microgreens.

• Castor Bean (Ricinus communis): This plant is notoriously toxic due to the presence of ricin, one of the most poisonous substances known. Even the tiny seedling is lethal if consumed.
• Foxglove (Digitalis purpurea): This flowering plant contains cardiac glycosides that are fatal to humans and should never be ingested in any form.

Other Common Problematic Plants

Beyond the nightshade and ornamental varieties, several other plants have parts that are toxic, which extends to their seedling stage. Careful selection is necessary to avoid these.

• Rhubarb: While the stalks of rhubarb are edible and a popular ingredient, the leaves contain high concentrations of oxalic acid and other toxic compounds. This toxicity is also present in the microgreen leaves.
• Kidney and Lima Beans (Phaseolus genus): Sprouted or raw beans from this family contain phytohaemagglutinin, a compound that is toxic and must be properly cooked to be neutralized. While most legumes are safe to sprout, this family presents a significant risk.

Comparison of Edible vs. Inedible Microgreens

Feature	Safe Microgreens (e.g., Broccoli, Radish, Peas)	Inedible Microgreens (e.g., Nightshades, Rhubarb Leaves)
Family	Brassicaceae, Fabaceae, Asteraceae, etc.	Solanaceae, Polygonaceae, wild species
Edible Parts	Entire stem and leaves	Often only the mature fruit or stalk (not the leaves)
Toxic Compounds	None present in edible stage	Alkaloids (solanine, tomatine), oxalic acid, ricin, cardiac glycosides
Sourcing	Use reputable, food-grade seed suppliers	Often mistakenly grown from garden seeds or wild seeds
Taste	Generally mild, nutty, or spicy	Can be bitter or unpalatable; toxicity is a key issue
Risk Level	Low, with proper handling	High, with potentially severe health consequences

The Dangers of Chemically Treated Seeds

For safe microgreen production, it is vital to only use untreated seeds specifically sold for sprouting or microgreen use. Many commercial garden seeds are coated with fungicides and other pesticides to protect them during traditional agricultural planting. These chemicals are not intended for immediate consumption and can be harmful if ingested in the concentrated form found on microgreen seeds. Always source seeds from trusted suppliers that guarantee their products are untreated and suitable for human consumption.

Conclusion

While microgreens offer a fantastic and nutritious way to enhance your diet, caution is necessary. The key is to be selective and informed about the species you are cultivating. Avoid any plants from the nightshade family, ornamental flowers like foxglove, and the leaves of plants like rhubarb. Always use untreated seeds from reputable sources and, if in doubt, opt for well-known edible varieties like radish, pea, or broccoli. Taking these simple precautions ensures that your microgreen growing experience remains a safe and healthy endeavor.

Why Microgreen Growers Should Be Cautious About Food Safety

Beyond toxic species, general food safety is also paramount. Microgreens are typically grown in warm, humid conditions that, if not properly managed, can become a breeding ground for harmful bacteria like Salmonella and E. coli. For small-scale growers, following Good Agricultural Practices (GAPs) is crucial. This includes sourcing clean seeds, using a sterile growing medium, maintaining proper hygiene, and storing the harvested greens correctly. These measures help prevent microbial contamination and ensure the microgreens are not only non-toxic but also safe from foodborne illness.

A List of Inedible Microgreens and the Reasons to Avoid Them

• Nightshade Family (Solanaceae): Includes tomato, potato, eggplant, and pepper. Inedible due to toxic alkaloids like solanine and tomatine.
• Ornamentals (e.g., Foxglove): Contains highly poisonous compounds such as cardiac glycosides, which can be fatal.
• Castor Bean: Contains the extremely toxic compound ricin, which is present even at the seedling stage.
• Rhubarb Leaves: High in oxalic acid and other harmful chemicals, making them toxic even as microgreens.
• Phaseolus genus (Some Beans): Raw or sprouted seeds of kidney and lima beans contain phytohaemagglutinin, which is toxic.
• Chemically Treated Seeds: Seeds intended for gardening may be coated with fungicides or pesticides that are not safe for consumption.
• Wild Plants: Unless you are a plant expert, do not grow wild seeds as microgreens due to the risk of misidentification and potential toxicity.

Final Recommendations for Safe Growing

When starting your microgreen journey, prioritize safety above all. Begin with well-known, safe varieties and purchase your seeds from a supplier that specializes in microgreen or sprouting seeds. If you are unsure about any plant, it is best to avoid it. Your health and safety are far more important than experimenting with an unknown variety. Choosing reputable sources and following best practices will ensure you can enjoy the many benefits of microgreens without any risk.

• For more information on safe microgreen production, see the Penn State Extension publication on the ABCs of Microgreens.

Frequently Asked Questions

Can you eat microgreens from the nightshade family?

No, you should never eat microgreens from the nightshade family, which includes plants like tomatoes, potatoes, and eggplants. These seedlings contain toxic compounds, such as alkaloids, that can cause illness.

Are microgreens from wild seeds safe to eat?

Unless you are a plant expert, you should avoid eating microgreens from wild seeds. Many wild plants contain toxic compounds, and it can be difficult to correctly identify them at the seedling stage.

Are the leaves of rhubarb microgreens edible?

No, rhubarb microgreen leaves are not edible. While the stalks of the mature plant are safe, the leaves are high in oxalic acid and other toxic chemicals, which are also present in the young leaves.

Why can't I use regular garden seeds for microgreens?

Regular garden seeds are often treated with fungicides and other chemicals to protect them from pests and diseases. These treatments are not safe for human consumption, especially when eating the plant at such an early stage.

What happens if you eat toxic microgreens?

The effects of eating toxic microgreens can range from mild digestive upset to severe poisoning, depending on the plant and the amount consumed. Symptoms can include vomiting, diarrhea, neurological issues, and, in severe cases, be fatal.

Which microgreens are safe for beginners to grow?

Beginners should start with safe and easy-to-grow varieties like radish, broccoli, peas, sunflower, and cabbage. These are widely available from reputable suppliers and are known to be edible and nutritious.

How can I ensure my microgreens are free of bacterial contamination?

To prevent bacterial contamination, use food-grade seeds, ensure your water is clean, use a sterile growing medium, maintain a clean growing environment, and wash your microgreens thoroughly before eating.