Safety & identification
The four rules that matter more than any profile: identify the plant, know the part, check the interactions, and keep the harvest clean.
A garden is a good place to meet a medicinal plant and a bad place to guess. This page collects the safety rules that apply across the whole index, with the plant-specific details kept on each profile.
Four rules before any harvest
- Identify the plant, not the label. A seed packet is a good start. A plant you inherited, found or bought unlabelled is not identified until you have checked the leaves, flowers, stems and root against a reliable description.
- Know which part is covered. Edible and toxic parts often sit on the same plant. Ginkgo seeds are toxic. Sweet violet roots and seeds are not edible. Rhubarb leaves are not the stalk. The profile names the part; do not improvise.
- Check the interaction list. Herbs can affect clotting, blood pressure, blood sugar, liver enzymes and sedation. If you take prescription medicine, ask a pharmacist before regular use.
- Keep the harvest clean. Avoid roadsides, sprayed lawns, dog routes and ground that may contain lead. Wash produce, dry it properly and label the jar with the plant name and date.
Lookalikes that matter
The highest-risk groups in this index are the carrot family (Apiaceae) and the daisy family (Asteraceae). The carrot family includes poison hemlock and water hemlock, both deadly. The daisy family includes many plants that cause contact dermatitis and some that are toxic to the liver.
| Group | Risk | Rule |
|---|---|---|
| Carrot family — dong quai, fennel | Poison hemlock and water hemlock share lacy leaves and umbel flowers | Grow from named seed. Never wild-collect a root or umbel. |
| Daisy family — calendula, chamomile, chrysanthemum, yarrow, elecampane, burdock, milk thistle | Allergy is common; some family members are toxic | Patch-test handling. Do not substitute one daisy for another. |
| Nightshade family — goji | Unripe fruit and other family members can be toxic | Eat only fully ripe fruit from a named plant. |
| Ginkgo | Seeds contain ginkgotoxin | Do not eat the seeds, ever. |
| Red berries generally | Many ornamental berries are toxic, especially to children | Do not harvest a red berry from an unidentified shrub or vine. |
Medication and pregnancy
Several herbs in this index have documented or theoretical interactions. The most important are:
- Bleeding risk: ginger, turmeric, ginkgo, licorice, peony, motherwort, red clover, chamomile, yarrow and others. Caution with warfarin, aspirin, clopidogrel and before surgery.
- Blood pressure and potassium: licorice is the clearest example; it can raise blood pressure and lower potassium with prolonged use.
- Blood sugar: burdock, nettle, milk thistle, goji and others may add to diabetes medication.
- Sedation: lemon balm, chamomile, lavender and valerian-type herbs can add to sleep medication or alcohol.
- Liver metabolism: schisandra, milk thistle and ginkgo can affect how some medicines are processed.
- Pregnancy: dong quai, motherwort, licorice, sage and several others carry explicit cautions. When in doubt, do not use a medicinal herb in pregnancy without professional advice.
This list is a prompt to ask a professional, not a complete interaction database. Your pharmacist can check a specific herb against your specific medicines.
Children and pets
Keep dried herbs, seeds and fresh berries out of reach. Children are more vulnerable to poisoning by weight, and pets investigate gardens differently from adults. Ginkgo seeds, unripe goji berries and many ornamental berries are the common garden risks. If a child has swallowed a plant, call poison control immediately.
If you suspect poisoning
Contact your local poison control centre or emergency services immediately. In the United States, call 1-800-222-1222. In the UK, call NHS 111 or 999 in an emergency. Do not wait for symptoms, do not induce vomiting unless told to, and have the plant or a photograph of it available for the clinician.
Garden hygiene and drying
Harvest in dry weather, early in the day, and process promptly. Dry herbs in a single layer with good airflow; mouldy material should be composted, not salvaged. Label every jar with the plant, the part, the date and the garden bed. A jar without a label is an anonymous plant, and an anonymous plant is not a safe one.
For drying methods by plant part, see the field guide How to dry and store herbs. For harvest timing, see Harvesting by plant part.