Tansy in Zone 5B — Great Plains

Tansy is a hardy perennial that offers both beauty and practicality in our Great Plains gardens. Its fern-like foliage and bright yellow flowers add a cheerful touch, and it’s known for its insect-repelling properties, which can be a real boon in our sometimes buggy summers. Plus, there's a certain satisfaction in growing something that can handle our variable weather.

Our region is known for its extreme temperature swings, occasional hail, and periods of drought. But with a 178-day growing season, you'll find that timing your Tansy planting just right can help it thrive despite these challenges. It’s more forgiving than some of the fussier herbs, making it a good choice for Plains gardeners.

Starting Tansy indoors isn't strictly necessary, but it can give you a head start, especially if you're eager for those first blooms. Begin in mid February through early March, 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 sunny windowsill or under grow lights.

Bottom watering is your friend here. Set the tray in a shallow dish of water and let the soil soak it up from the bottom. This helps prevent damping-off, a common problem with seedlings. Keep in mind that spring in the Plains can be unpredictable, so be prepared to adjust your transplanting schedule if we get a late cold snap.

Transplant your Tansy seedlings outdoors in early April through early May, once the danger of hard frost has passed. Before planting, harden them off by gradually exposing them to outdoor conditions for about a week. Start with an hour or two of shade, increasing the time and sun exposure each day.

Space the plants 12-18 inches apart to give them room to grow. Keep an eye on the weather forecast around transplant time, as we can still get some chilly nights or even a late frost. If frost threatens, cover your seedlings with a frost blanket or overturned pots.

Direct sowing Tansy is a simple and effective method, aligning well with the Plains gardener's practical approach. Sow the seeds directly into the garden in early April through mid July. Choose a sunny spot with well-drained soil.

Prepare the soil by loosening it and removing any weeds. Lightly press the seeds into the soil – they need light to germinate. Keep the soil consistently moist until the seedlings emerge. Thin the seedlings to 12-18 inches apart once they are a few inches tall. Direct sowing works well, but you'll need to be patient and diligent about weeding until the plants get established.

Tansy is remarkably drought-tolerant, making it a good fit for our variable rainfall patterns in the Great Plains. Once established, it thrives on neglect. Overwatering is far more detrimental than underwatering, and can encourage overly aggressive growth.

During the hottest parts of summer, when temperatures climb into the 90s, check the soil moisture with the finger test. Stick your finger about two inches deep into the soil near the base of the plant. If it feels dry, it's time to water. Aim for about an inch of water per week, either from rainfall or irrigation. Water at the base of the plant rather than overhead to minimize the risk of fungal diseases in our low-to-moderate humidity.

Signs of underwatering include wilting or drooping leaves, while overwatering can lead to yellowing leaves and potentially root rot. A layer of mulch, like wood chips or straw, can help retain moisture in the soil and reduce the need for frequent watering.

Pruning Tansy is essential to keep it from taking over your garden and to encourage continued growth. The main goal is to deadhead the spent flowers. This prevents the plant from self-seeding, which it does with enthusiasm.

Throughout the growing season, from midsummer onward, snip off the flower heads as soon as they start to fade. In the fall, after the first frost around mid- October, cut the plant back to the ground. This helps tidy up the garden and prepares the plant for winter dormancy. Because Tansy is so vigorous, consider planting it in a contained area or using barriers to prevent it from spreading into unwanted areas.

You can begin harvesting Tansy leaves as early as mid June, about 75 days after planting, and continue through late October. The plant is typically ready to harvest once it has established a good amount of foliage. Look for the button-like yellow flowers, which usually bloom in midsummer. Tansy is primarily used as an insect repellent, not for culinary purposes, as it can be toxic in large amounts.

To harvest, simply snip off the stems with leaves, using scissors or pruning shears. Avoid taking more than one-third of the plant at any one time to ensure continued production. As the first frost approaches in mid- October, harvest any remaining foliage you want to use. You can dry the leaves for later use as an insect repellent.

Tansy is generally a low-maintenance plant, but there are a couple of common problems to watch out for in the Great Plains.

Can be Invasive

• What it looks like: Tansy spreads rapidly, popping up in unwanted areas of your garden.
• What causes it: Tansy is a vigorous self-seeder and spreads through rhizomes. Our fertile prairie soil and plentiful sunshine contribute to its rapid growth.
• How to fix/prevent it: Deadhead flowers regularly to prevent seed production. Plant Tansy in a contained area or use barriers to prevent it from spreading. Dig up and remove unwanted plants as soon as they appear.

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: 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: Our region's hot summers and variable rainfall can exacerbate these problems. The heat can stress the plants, making them more susceptible to aphids, while alternating periods of drought and heavy rain can encourage invasive spread. Keep a close eye on your Tansy and take action promptly to address any issues.

Tansy can be a beneficial companion plant in the Great Plains garden, offering protection to certain crops. It's a good companion for potatoes, squash, and cucumbers because its insect-repelling properties help deter pests that commonly attack these plants. It also benefits raspberries by repelling raspberry beetles.

Avoid planting Tansy near certain herbs, as it can inhibit their growth. Keep it away from fennel and members of the cabbage family, as these plants do not thrive when grown near Tansy. By choosing the right companions, you can create a thriving and pest-resistant garden, even with our Plains climate challenges.