Tansy in Zone 6B — Midwest

Tansy is a worthwhile addition to any Midwest garden. It's incredibly easy to grow, offers beautiful button-like yellow flowers, and acts as a natural insect repellent. Plus, it's a perennial, meaning it will come back year after year, even after our cold winters.

While Midwest weather can be unpredictable, with late frosts in spring and summer heat spells, Tansy is quite hardy. Our 183-day growing season gives you plenty of time to get a good harvest, and Tansy's adaptability makes it a forgiving plant for beginners.

Starting Tansy indoors isn't strictly necessary, but it can give you a head start, especially if you're eager to see those yellow blooms as early as possible. If you choose to start indoors, aim for mid February through early March, about six weeks before you plan to transplant.

Use seed trays with a good seed-starting mix and provide warmth and light. Bottom watering is a great way to keep the soil consistently moist without disturbing the delicate seedlings. Keep in mind that our springs in the Midwest can be quite variable, so starting indoors gives you some control over the plant's environment before it faces the unpredictable weather.

Transplant your Tansy seedlings outdoors in early to late April, after the risk of a hard frost has passed. Before transplanting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the sun and wind.

Space the plants 12-18 inches apart in well-drained soil. Keep an eye on the weather forecast; a late frost can still happen in the Midwest, so be prepared to cover your transplants if necessary.

Direct sowing Tansy is a simple and effective method, especially if you don't want to fuss with starting seeds indoors. Sow seeds directly into the garden from early April through mid July. Choose a location with full sun to part shade.

Prepare the soil by loosening it and removing any weeds. Tansy isn't too picky about soil, but good drainage is essential. Space the seeds 12-18 inches apart. Direct sowing is convenient, but keep in mind that the plants will take longer to mature compared to transplants.

Tansy is incredibly drought-tolerant, making it a great choice for Midwest gardens, even during summer heat spells. Once established, it thrives on neglect, so resist the urge to overwater. Too much water can actually make it more aggressive.

During the spring, when rainfall is more frequent, you likely won't need to water Tansy at all unless we're experiencing a particularly dry spell. In the summer, when temperatures rise and humidity is moderate-to-humid, check the soil before watering. Use the "finger test" – stick your finger about 2 inches deep into the soil. If it feels dry, it's time to water. Aim for about 1 inch of water per week, either from rainfall or supplemental watering.

Water at the base of the plant to avoid wetting the foliage, especially given our moderate-to-humid summers, which can promote fungal diseases. Yellowing leaves can be a sign of overwatering, while wilting can indicate underwatering. Adding a layer of mulch around the base of the plant helps retain moisture and suppress weeds, which is especially useful in our sometimes wet-summer climate.

Pruning Tansy is essential to keep it under control and prevent it from becoming too invasive in your Midwest garden. Deadhead the flowers regularly throughout the growing season to prevent self-seeding. Simply snip off the spent flower heads as they fade.

In late fall, after the first frost (around mid- October in the Midwest), cut the plants back to the ground. This helps tidy up the garden and prepares the plants for winter dormancy. Remember, Tansy is vigorous, so don't be afraid to prune it back hard if necessary.

You can expect your first harvest of Tansy from mid June through late October, about 75 days after planting. The best time to harvest is when the button-like yellow flowers are in full bloom, usually midsummer. While Tansy is used as an insect repellent, it's important to note that it's not for culinary use and can be toxic in large amounts.

To harvest, simply cut the stems with flowers using pruning shears or scissors. Be careful not to damage the surrounding plant. Regular harvesting encourages continued production of flowers throughout the growing season. As the first frost approaches in mid- October, you can harvest the remaining stems to dry for later use as an insect repellent.

Tansy is relatively low-maintenance, but there are a couple of common problems that Midwest gardeners might encounter: it can be invasive, and it can attract aphids.

Invasive Spread

• What it looks like: Tansy spreads quickly through both seeds and rhizomes, potentially taking over garden beds and crowding out other plants.
• What causes it: Tansy is a vigorous grower and readily self-seeds. Our fertile soil in the Midwest provides ideal conditions for its spread.
• How to fix/prevent it: Contain Tansy by planting it in a raised bed or using underground barriers to prevent rhizome spread. Deadhead flowers regularly to prevent seed production. Be vigilant about removing unwanted seedlings.

Aphids

• What it looks like: Clusters of tiny soft-bodied insects (green, black, or white) on stems and leaf undersides. Sticky honeydew residue. Curled or distorted new growth.
• What causes it: Rapid-reproducing sap-sucking insects. Populations explode in warm weather. Ant colonies may farm them for honeydew. Our moderate-to-humid summers can create favorable conditions for aphid infestations.
• How to fix/prevent it: Strong water spray knocks them off. Encourage ladybugs and lacewings (natural predators). Insecticidal soap for heavy infestations. Neem oil works systemically. Avoid excess nitrogen fertilizer (it attracts them).

Midwest Specific Challenges: Our moderate-to-hot heat, moderate-to-humid humidity, and wet-summer rainfall can exacerbate both of these issues. The warm, humid conditions encourage aphid populations, while the ample rainfall and fertile soil contribute to Tansy's aggressive growth. Vigilance and proactive measures are key to keeping these problems under control.

Tansy makes a good companion plant for several vegetables in the Midwest garden. It repels certain pests, benefiting nearby plants.

Good companions include potatoes, squash, and cucumbers. Tansy repels potato beetles, squash bugs, and cucumber beetles, protecting these crops from damage. It's also a good companion for raspberries, as it can deter certain raspberry pests. Avoid planting Tansy near Brassicas like cabbage and broccoli, as it can inhibit their growth.