Tansy in Zone 3B — Great Plains

Tansy is a tough, old-fashioned herb that's right at home in the Great Plains. Its fern-like foliage and sunny yellow blooms add a cheerful touch to your garden, and it's known for repelling insects, which is a welcome benefit with our variable weather patterns. Plus, it's surprisingly drought-tolerant, making it a low-maintenance choice for our region.

Our extreme weather can be a challenge, but Tansy's resilience makes it a rewarding plant to grow. With a growing season of around 118 days, timing is important, but you'll find it's very manageable to get a good harvest. You have a solid window of opportunity to get it established.

Starting Tansy indoors is certainly an option, but honestly, it's not usually necessary here on the Plains. It's so vigorous, direct sowing often works just fine. However, if you're itching to get a head start, or want to ensure a more even stand, starting indoors can be helpful.

If you choose to start indoors, aim for mid-March through early April, about six weeks before you plan to transplant. Use seed trays with a good seed-starting mix and keep them in a warm spot with plenty of light – a south-facing window or under grow lights works well. Bottom watering helps prevent damping off and keeps the seedlings evenly moist. Remember, our spring weather can be variable, so be prepared to adjust your schedule based on how quickly things are warming up outside.

Transplanting Tansy seedlings outdoors is best done in early May through early June, once the danger of a hard frost has passed. Before you plant, you'll want to harden off your seedlings by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the wind and temperature swings that are common here.

Choose a spot with full sun to part shade and space the plants 12-18 inches apart. Our Plains weather can still be unpredictable in May, so keep an eye on the forecast and be ready to protect young plants from late frosts or sudden hail.

Direct sowing Tansy is a straightforward method that suits our Plains climate well. It's a reliable way to get these hardy plants established.

Sow seeds directly into the garden in early May through mid-June. The soil should be workable and the soil temperature consistently above 60°F. Lightly rake the soil to create a fine seedbed, scatter the seeds evenly, and gently press them into the soil. Keep the soil consistently moist until germination, which usually takes about two weeks. Thin seedlings to 12-18 inches apart.

Tansy is incredibly drought-tolerant, which is a huge advantage in our variable Plains climate. Once established, it actually thrives on neglect, so resist the urge to overwater it. Too much water or fertilizer makes it even more aggressive.

During the first few weeks after planting or transplanting, water regularly to help the plants establish strong roots. After that, you'll only need to water during extended dry spells. A good rule of thumb is to check the soil moisture about two inches deep – if it's dry to the touch, it's time to water.

When you do water, aim for about an inch of water per week. Water at the base of the plant to avoid wetting the foliage, which can encourage fungal diseases in our low-to-moderate humidity. Signs of underwatering include wilting or drooping leaves. Overwatering can cause yellowing leaves and root rot.

A layer of mulch around the base of the plants helps conserve moisture and suppress weeds, which is especially helpful during our hot, dry summers. Use something like shredded bark or straw.

Pruning Tansy is mainly about keeping it in check and preventing it from becoming too invasive. Deadheading is key.

Throughout the growing season, deadhead spent flowers to prevent the plant from self-seeding. This is especially important if you're concerned about it spreading too much. In late fall, after the first frost around mid-September, cut the plant back to the ground. This helps tidy up the garden and encourages fresh growth in the spring. If you want to contain it, consider planting it in a pot or using barriers to prevent the roots from spreading.

You can expect your first harvest of Tansy starting in mid-July and continuing through late September, about 75 days after planting. The button-like yellow flowers will be in full bloom by midsummer.

Remember, Tansy is primarily used as an insect repellent and is not recommended for culinary use due to its potential toxicity in large amounts. To harvest, simply cut the stems at the base of the plant, taking what you need. Regular harvesting encourages continued production.

As the first frost approaches in mid-September, you can harvest the remaining foliage and flowers for drying. Hang them upside down in a cool, dark place to dry, then store them in airtight containers for use as an insect repellent.

Tansy is generally a tough plant, but here on the Plains, you might run into a couple of common problems.

Can be invasive

• What it looks like: Tansy spreads aggressively, forming dense clumps and potentially crowding out other plants in your garden.
• What causes it: Tansy spreads through both seeds and underground rhizomes. Our fertile prairie soil and intense sunshine create ideal conditions for its vigorous growth.
• How to fix/prevent it: Contain Tansy by planting it in a pot or using physical barriers to prevent the roots from spreading. Regularly deadhead spent flowers to prevent self-seeding. If it's already spreading, dig up unwanted plants, being sure to remove as much of the root system as possible.

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.
• How to fix/prevent it: A strong spray of water can knock them off. Encourage ladybugs and lacewings (natural predators). Insecticidal soap works well, as does neem oil. Avoid excess nitrogen fertilizer.

Great Plains Specific Challenges: Our hot summers, low-to-moderate humidity, and variable rainfall can stress plants, making them more susceptible to problems. The wind can also spread aphids and seeds, so wind protection is essential. Monitor your plants regularly and take action quickly to address any issues.

Tansy can be a good companion plant in the Great Plains garden, but use it strategically.

Good companions:

• Potatoes: Tansy is said to repel potato beetles, a common pest in our region.
• Squash & Cucumber: Tansy can help deter squash bugs and cucumber beetles.
• Raspberries: Tansy is thought to deter certain raspberry pests.

Avoid planting Tansy near herbs or vegetables that are sensitive to its allelopathic properties. Because it can be invasive, keep it away from delicate plants.