Flat yellow button flowers and camphor-scented blooms draw hoverflies and ladybirds, while flies, ants and aphids keep well away. Tansy (Tanacetum vulgare) gives repellent and fungicidal sprays as well as feeding pollinators, and it asks little in return: good drainage, and it is one of the easiest plants to grow.
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Some insects flee it, while others love to nestle right in its center.
On the other hand, wasps and predator wasps, ladybugs and hoverflies love it for the pollen and nourishment it offers. It is even noted to inhibit the laying of eggs and feeding of larvae for some insect species that typically cause heavy damage in the vegetable patch, such as the colorado potato beetle and the cabbage moth.
Tansy spreads by creeping rhizomes and will march into neighbouring beds.
Sinking a bottomless pot or a buried edging strip around the clump keeps those runners where you want them.
Keep tansy out of paddocks and pasture edges, because grazing horses and cattle can be poisoned by it.
Tansy can be fermented, infused or macerated, and each preparation asks for a different quantity of plant material, a different waiting time and a different dilution. This table sets the three side by side so you can pick the one that matches the problem you are treating.
| Preparation | Plant material per volume of water | Waiting time | Dilution before spraying | Best used against |
|---|---|---|---|---|
| Fermented tansy tea | 1 lb fresh (or 1½ oz dried) for 5 quarts / 1 kg for 10 l | Until the mix stops bubbling, stirred daily | Thin to 5 or 10% (1 volume in 9 or 19 of water) | Preventive spray against vegetable patch pests, rust and mildew |
| Infusion of the whole plant | About 10 oz (300 g) of stem, roots, leaves and flowers per quart or litre | Steep, covered, for an entire day | Dilute 1:9 (10%) | Ants, owlet moths, flies and sawflies |
| Flower maceration | 1 oz dried flowers (30 g), or about 10 oz fresh (300 g), per quart or litre | Three days outdoors in full sun | None, use it directly | Rust and mildew |
Fermenting draws out the most from the plant, while the infusion and the maceration are quicker to have ready.
Fermenting will extract nutrients and active compounds best, but the other methods are faster and easier to prepare. Pair it with
First step in preparing a fermented extract is to harvest your tansy! You’ll need about 1 pound fresh material for 5 quarts water (more or less 1 kg for 10 liters). If you use dried material, divide the amount by ten: 1½ oz for 5 quarts, or 100g for 10 l.
Pour your fermented tea in bottles and store these away from light. Take note that, as such, the mix is concentrated: you have to thin it to a 5 or 10% mix before spraying (1 volume mix plus 9 or 19 volumes water). This spray is excellent when used as a preventive treatment to repel vegetable patch pests and keep rust and mildew from appearing.
→ Use or prepare this together with nettle fertilizer to hit two birds with one stone!
Boil a quart or liter of rainwater, and chop up about 10 ounces (300g) of tansy. Use the whole plant: stem, roots, leaves, flowers (if any). Place the tansy in a non-metal bowl or container and cover with the boiling water. Cover it over and let it steep an entire day. Filter your infusion and transfer it to a bottle for storage and keeping. Dilute it 1:9 (10%) before use. Excellent to repel ants, owlet moths, flies and sawflies.
You’ll need 1 ounce of dried flowers (30g), equivalent to around 10 oz of fresh flowers (300g).
Follow recommended doses for each particular use: since tansy contains thujone, a toxic compound, mistakes can be dangerous. When the dosage is small, tansy is beneficial. When doses are too high, or the plant is taken too often, it becomes toxic and even triggers miscarriages. Definitely not a plant extract for pregnant women!
Never swallow tansy essential oil, not even a diluted drop.
Slip dried tansy sprigs among woollens or under a dog’s bed, where the camphor scent helps keep moths and fleas away.
Do not throw tansy clippings onto pasture or into a rabbit hutch: eaten in quantity the plant poisons horses, cattle and small livestock.
Convinced yet? Wouldn’t it be a great idea to have a little tansy at hand? At the very least, pollinators will consider the camphor-scented blooming a real treat! It is a very easy plant to grow, as long as drainage is good. It’ll thrive in poor, and even limestone soil. It does prefer cool soil, and doesn’t really like excess acidity. Better place it in sun or part shade, either in containers or directly in the ground.
Planting is most successful in Spring and Fall, and spacing should be at least 30 inches (50 cm) between plants. If growing in a pot, layer the bottom of the pot with clay marbles for drainage. Outside in the ground, water only upon planting, and then again in case of prolonged dry spells.
Harvest leaves in May-June: cut the entire stem with the leaves still attached. Harvest flowers in September. In Autumn, cut the plant back to a short clump, and you’ll see it bounce back to life in Spring. You can use it fresh, direct from the plant, or you can dry it by hanging a bouquet upside-down.
Wear gloves when cutting tansy, since the sap irritates sensitive skin.
Cut the flower heads while the yellow buttons are fully open and still bright, before their edges start browning.
Wait until the dew has dried off the foliage, because damp stems tend to go mouldy instead of drying in a hanging bundle.
Leave a few flower heads uncut for hoverflies and ladybirds.
