Tansy in Zone 6B — Great Plains

Tansy is worth growing here in the Great Plains, even if you don't plan to ingest it. The intensely fragrant foliage is a natural insect repellent, which is always welcome with our variable weather patterns and the pests they can bring. Plus, the bright yellow flowers offer a cheerful pop of color, even in the face of our sometimes relentless sunshine.

Our region's extreme temperature swings and occasional hail can be tough on plants. But Tansy is surprisingly hardy, and with a good start within our 198-day growing season, you'll find it a low-maintenance addition to your garden.

Starting Tansy indoors is an option, particularly if you're further north in the Plains where the growing season can feel even shorter. Starting seeds indoors from early to late February gives you a head start.

Use seed trays with a good seed-starting mix, and keep them warm (around 70°F) and under grow lights. Bottom watering will help prevent damping off – just set the tray in a shallow pan of water and let the soil soak it up. Keep in mind that our variable spring weather can make transplanting tricky, so watch the forecast closely.

Transplanting your Tansy seedlings outdoors from late March through late April allows them to get established before the heat of summer kicks in. Before transplanting, harden them off for about a week by gradually exposing them to outdoor conditions.

Choose a spot with full sun to partial shade, and space the plants 12-18 inches apart. Keep an eye on the weather forecast – a late frost or a bout of strong winds can set them back.

Direct sowing Tansy is a perfectly viable option, especially if you prefer a more hands-off approach. Sow seeds from late March through late July, once the soil has warmed up a bit.

Prepare the soil by loosening it and removing any rocks or debris. Sprinkle the seeds lightly on the surface and gently press them in. The main drawback to direct sowing is that you'll need to stay on top of weeding until the seedlings are established. Space plants 12-18 inches apart.

Tansy is exceptionally drought-tolerant, making it a perfect fit for our variable rainfall patterns here in the Great Plains. Once established, it practically thrives on neglect. Overwatering or over-fertilizing can actually make it too aggressive.

During the spring, while the plants are getting established, water them deeply but infrequently – about once a week, or when the top two inches of soil feel dry to the touch (use the "finger test"). In the heat of summer, you might need to water them every week or two, depending on rainfall. 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, especially with our occasional humidity spikes. Signs of underwatering include wilting or drooping leaves. Overwatering can lead to yellowing leaves and root rot. A light layer of mulch around the base of the plants can help retain moisture and suppress weeds.

Deadheading is key to keeping Tansy from taking over your garden. Once the button-like yellow flowers start to fade, snip them off to prevent self-seeding. You can do this throughout the growing season, from early June through late October.

In the fall, after the first frost, cut the plants back to the ground. This will help keep them tidy and prevent them from becoming too woody. Given how vigorous Tansy can be, you might want to consider growing it in a container or using barriers to contain its spread.

You can start harvesting Tansy as soon as the plants are large enough, typically from early June through late November. The peak harvest time is when the button-like yellow flowers are in full bloom, usually midsummer.

Harvest the foliage by cutting the stems with sharp scissors or pruners. Avoid harvesting more than a third of the plant at a time to ensure continued production. As first frost approaches in late October, harvest any remaining foliage for drying or other uses.

Two common problems with Tansy in the Great Plains are its invasive nature and aphid infestations.

Invasive Spread

• What it looks like: Tansy spreads quickly via rhizomes (underground stems), popping up in unwanted areas of the garden.
• What causes it: Its vigorous growth habit and ability to tolerate a wide range of conditions make it prone to spreading. Our fertile prairie soil only encourages this.
• How to fix/prevent it: Plant Tansy in containers or use physical barriers (like edging) to contain its roots. Regularly remove any unwanted shoots that pop up.

Aphids

• What it looks like: Clusters of tiny (green, black, or white) insects 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 fluctuating temperatures in spring and fall can lead to population booms.
• 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).

Great Plains Specific Challenges: The hot summers and variable rainfall in the Great Plains can stress Tansy, making it more susceptible to pests and diseases if not properly managed. However, its drought tolerance means it can generally withstand our dry spells better than many other plants.

Tansy makes a good companion plant for several crops in the Great Plains garden. It repels many insects, benefiting:

• Potatoes: Tansy helps deter potato beetles.
• Squash & Cucumbers: Tansy can deter squash bugs and cucumber beetles.
• Raspberries: Tansy can help repel raspberry beetles.