Tansy in Zone 7A — Southeast

Tansy is worth growing in your Southeast garden, mainly for its ability to repel insects. While not for the dinner table, it's a powerhouse in the garden, protecting your prized veggies. Plus, those bright yellow button-like flowers add a cheerful touch to the landscape during our long summer.

We all know gardening in the Southeast comes with its share of challenges, namely humidity and pests. But don't let that deter you. With our long growing season (around 225 days) and some smart planning, you can easily grow Tansy.

Starting Tansy indoors gives you a head start, but it's not essential in our climate. If you want to get a jump on the season, start your seeds indoors from late January through mid February, about six weeks before you plan to transplant.

Use seed trays with a good seed-starting mix. Keep them consistently moist, and bottom watering works wonders to prevent damping-off. Place the trays under grow lights or in a very sunny window. Remember our spring weather can be moderate, so starting indoors gives you more control over the environment early on.

Transplant your Tansy seedlings outdoors from mid March through early April, once the threat of frost has passed. Before planting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week. This prepares them for the real world.

Choose a spot with full sun to part shade, and space the plants 12-18 inches apart. Keep an eye on the forecast – those late-season cold snaps can still happen in early spring around here.

Direct sowing Tansy is a perfectly viable option in the Southeast. You can sow seeds directly into the garden from mid March through early August. This gives you a long window of opportunity.

Prepare the soil by loosening it and removing any weeds. Since we have clay soil, amend with compost to improve drainage. Sow the seeds shallowly and keep the soil consistently moist until they germinate. Thin the seedlings to 12-18 inches apart. Direct sowing is easier, but you'll have to be diligent about weed control.

Tansy is incredibly drought-tolerant, which is a blessing during our hot summers. Once established, it thrives on neglect, so don't overdo the watering. Too much water or fertilizer will only make it more aggressive.

During the spring and fall, when rainfall is more consistent, you probably won't need to water at all unless we're experiencing a dry spell. In the heat of the summer, check the soil moisture with the finger test. Stick your finger about two inches deep into the soil. 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 to avoid wetting the foliage, which can encourage fungal diseases in our humid climate. Yellowing leaves can indicate overwatering, while wilting leaves signal underwatering. Mulching around the base of the plant with pine straw or wood chips helps retain moisture and suppress weeds.

Deadheading Tansy is crucial to prevent it from taking over your garden. Remove the spent flowers as soon as they fade to prevent self-seeding. Our long growing season means it will keep producing flowers if you deadhead regularly.

In the fall, after the first frost around early November, cut back the entire plant to the ground. This helps keep it tidy and encourages new growth in the spring. Tansy is vigorous, so consider planting it in a container or using barriers to contain its spread.

You can expect your first harvest of Tansy foliage from late May through mid November, about 75 days after planting. The plant is ready to harvest when it has established foliage and the button-like yellow flowers bloom midsummer. Tansy is valued for its insect-repelling properties, not for culinary use, as it can be toxic in large amounts.

To harvest, simply snip off stems with foliage as needed. Avoid taking more than one-third of the plant at a time to ensure continued production. As the first frost approaches in early November, you can harvest the remaining foliage for drying and use during the winter months.

Tansy is generally a low-maintenance plant, but there are a couple of issues you might encounter in the Southeast: invasiveness and aphids.

Invasiveness

• What it looks like: Tansy spreads aggressively, forming dense clumps and potentially crowding out other plants.
• What causes it: Tansy self-seeds readily and spreads through rhizomes. Our long growing season gives it ample opportunity to reproduce.
• How to fix/prevent it: Deadhead regularly to prevent seed formation. Plant in containers or use underground barriers to contain the spread. Remove any unwanted seedlings promptly.

Aphids

• What it looks like: Clusters of tiny, soft-bodied insects (green, black, or white) on stems and leaf undersides. You might also see a sticky honeydew residue and curled or distorted new growth.
• What causes it: Aphids are sap-sucking insects that thrive in warm weather. Populations can explode quickly. Ants may farm them for honeydew.
• How to fix/prevent it: Knock aphids off with a strong spray of water. Encourage natural predators like ladybugs and lacewings. For heavy infestations, use insecticidal soap or neem oil. Avoid excess nitrogen fertilizer, which attracts them.

Southeast Specific Challenges The hot, humid summers and wet-summer rainfall in the Southeast can exacerbate both of these problems. The humidity encourages aphid populations, and the long growing season allows Tansy to spread more aggressively. Vigilance and proactive measures are key to keeping these issues under control.

Tansy is a great companion plant for several vegetables in the Southeast garden. It repels insects, which benefits plants like potatoes, squash, and cucumbers. Planting Tansy near raspberries can help deter raspberry beetles.

Avoid planting Tansy near brassicas (cabbage, broccoli, kale) as it can attract cabbage moths. Keep it away from herbs like mint, as Tansy can be invasive and outcompete them.