Tansy in Zone 6B — Northeast

Tansy is worth growing in your Northeast garden for its potent insect-repelling properties, a valuable asset with our sometimes-humid summers that can bring out all sorts of pests. Plus, the bright yellow blooms add a cheerful touch to the landscape. It's a low-maintenance perennial that can handle our cool nights and even thrives on a little neglect, which is perfect for busy gardeners.

We know our short growing season (about 183 days) and potential for late spring frosts can be a challenge. But don't worry, Tansy is quite hardy and with a little planning, you can easily fit it into your garden schedule. You'll be enjoying its benefits from mid-June all the way through late October.

Starting Tansy indoors in the Northeast is an option, but not always necessary since it direct sows so easily. If you want a head start, aim to sow seeds indoors from 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 (a heat mat helps) and plenty of light.

Bottom watering is a great way to keep the soil consistently moist without overwatering, which can be an issue with seedlings. Place the tray in a shallow dish of water and let the soil soak it up. Remember that our spring weather can be unpredictable, so indoor starting gives you some flexibility if we have a late cold snap.

Transplant your Tansy seedlings outdoors in early to late April, once the risk of hard frost has passed. Before planting, be sure to harden them off by gradually exposing them to outdoor conditions for about a week. This will help them adjust to the cooler temperatures and stronger sunlight.

Space the plants 12-18 inches apart in well-drained soil. Keep an eye on the weather forecast around transplant time. If a late frost threatens, be prepared to cover the seedlings with row covers or blankets.

Direct sowing Tansy is a straightforward method, especially if you're not in a rush. Sow the seeds directly into the garden from early April through mid-July. Tansy seeds need light to germinate, so don't bury them too deeply – just press them lightly into the soil.

Make sure the soil is relatively warm before sowing. While Tansy is hardy, germination is better when the soil temperature is consistently above 50°F. Space the seeds about 12-18 inches apart. Direct sowing is easy, but keep in mind that the plants will take longer to mature compared to transplants.

Tansy is very drought-tolerant, making it a great choice for our sometimes-unpredictable Northeast summers. Once established, it thrives on neglect. Overwatering can actually make it more aggressive, which you definitely want to avoid.

During the spring, when the plants are getting established, water them regularly – about once a week if we're not getting much rain. Once they're mature, you'll only need to water during extended dry periods. Use the "finger test" – stick your finger about two inches into the soil. If it feels dry, it's time to water. In general, aim for about an inch of water per week during dry spells.

Water at the base of the plant to avoid getting the foliage wet, especially in our moderate-to-humid climate. Overhead watering can increase the risk of fungal diseases. Signs of underwatering include wilting leaves, while overwatering can cause yellowing leaves and root rot. Applying a layer of mulch around the base of the plants helps retain moisture in the soil and suppress weeds.

Pruning Tansy is mainly about managing its spread. Deadhead the flowers regularly throughout the season to prevent aggressive self-seeding. This is especially important if you're trying to contain it within a specific area of your garden.

Simply snip off the spent flower heads with garden shears. In late fall, after the first frost around mid- October, cut the plant back to the ground. This will help tidy up the garden and prepare the plant for winter dormancy.

You can expect your first Tansy harvest starting around mid-June, and continuing through late October. Tansy is not for culinary use. It's used as an insect repellent. The button-like yellow flowers bloom in midsummer and are a good indicator that the plant is mature.

To harvest, simply cut the stems with garden shears or scissors. You can hang the stems upside down to dry them for later use. Regular harvesting will encourage continued production throughout the season. As the first frost approaches in mid- October, you can harvest the remaining stems for drying.

Here are two common problems you might encounter with Tansy in the Northeast:

Invasive Spread

• What it looks like: Tansy can quickly spread beyond its intended area, popping up in unwanted locations throughout your garden.
• What causes it: Tansy is a vigorous grower and readily self-seeds. Our moderate heat and even rainfall during the summer provide ideal conditions for seed germination and plant growth.
• How to fix/prevent it: The best way to prevent Tansy from becoming invasive is to contain it with physical barriers, such as edging or planting it in a raised bed. Deadheading the flowers before they go to seed is also crucial. If it does spread, promptly remove unwanted plants, being sure to dig up the roots.

Aphids

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

Northeast Specific Challenges: Our moderate heat, moderate-to-humid humidity, and even rainfall can create ideal conditions for both Tansy growth and potential pest problems like aphids. Regular monitoring and proactive measures are key to keeping your Tansy healthy and contained.

Tansy can be a helpful companion plant in the Northeast garden:

• Potato, Squash, Cucumber: Tansy repels potato beetles, squash bugs, and cucumber beetles, all common pests in our region.
• Raspberry: Tansy helps deter raspberry beetles.

Avoid planting Tansy near brassicas (cabbage, broccoli, kale) as it can attract cabbage moths. It's also best to keep it away from herbs like mint and basil, as its strong scent can overpower their flavors.