Tansy in Zone 6B — Pacific Northwest

Tansy is a fantastic addition to any Pacific Northwest garden, offering more than just a pretty face. Its strong scent makes it an excellent natural insect repellent, protecting your other plants. Plus, its cheerful yellow blooms add a pop of color to your garden even during our mild summers.

Our 162-day growing season in the PNW means we need to be smart about timing. While Tansy is hardy, getting it established at the right time will ensure it thrives. Don't worry about late blight or our cool spring soils; Tansy is pretty resilient once it gets going.

Starting Tansy indoors isn't strictly necessary, but it can give you a head start, especially if you're aiming for earlier blooms. Sow seeds indoors from late February through mid 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.

Bottom watering is ideal to prevent damping off, which can be a problem during our overcast spring days. Remember, our springs are often slow to warm up, so indoor starting helps overcome that.

Transplant your Tansy seedlings outdoors from mid April through mid May, after the danger of hard frost has passed. Before transplanting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the temperature swings we sometimes experience in spring.

Space your Tansy plants 12-18 inches apart to allow for their clumping growth habit. Even in late spring, our soil can still be cool, so be gentle when transplanting to avoid shocking the roots.

Direct sowing Tansy is a straightforward method, especially if you're not in a rush for early blooms. Sow seeds directly into your garden beds from mid April through mid July. Choose a spot with full sun to part shade.

Prepare the soil by loosening it and removing any weeds. Tansy isn't too picky about soil, but good drainage is always a plus in our wet springs. Space the seeds 12-18 inches apart. Keep the soil consistently moist until the seedlings emerge.

Tansy is incredibly drought-tolerant and thrives on neglect, which is great news for PNW gardeners who often have less time to water during our dry summer months. Once established, you'll rarely need to water it. In fact, overwatering can make it even more aggressive.

During the dry summer months, check the soil moisture with the "finger test." Stick your finger about 2 inches deep into the soil near the base of the plant. If it feels dry, give it a good watering, aiming for about 1 inch of water per week. Water at the base of the plant rather than overhead. Our dry-summer humidity means foliar diseases aren't usually a big concern, but it's still best to avoid wetting the leaves unnecessarily.

Signs of underwatering include wilting or drooping leaves. Overwatering can lead to yellowing leaves and potentially root rot, especially in our heavier clay soils. A layer of mulch around the base of the plant can help retain moisture during the summer and suppress weeds.

Pruning Tansy is mainly about deadheading and controlling its spread. Deadhead spent flowers throughout the growing season to prevent aggressive self-seeding. This will help keep it from taking over your garden, which it's fully capable of doing!

In the fall, after the first frost around early October, cut the plant back to the ground. This helps tidy up the garden and prepares the plant for winter dormancy. Don't worry, it'll bounce back vigorously in the spring.

You can expect your first Tansy harvest starting in early July and continuing through mid October. Tansy is primarily grown for its insect-repelling properties and attractive blooms, rather than culinary use. The button-like yellow flowers bloom midsummer and are a good indicator that the plant is mature.

To harvest, simply cut the stems with flowers. Harvest regularly to encourage continued production and prevent the plant from going to seed. As the first frost approaches in early October, you can harvest the remaining stems for use as dried insect repellent.

Tansy is generally a low-maintenance plant, but here are a couple of common problems you might encounter in the Pacific Northwest:

Can be Invasive:

• What it looks like: Tansy spreads quickly via rhizomes and seeds, potentially taking over garden beds and crowding out other plants.
• What causes it: Its vigorous growth habit combined with our mild climate allows it to thrive and spread rapidly.
• How to fix/prevent it: Plant Tansy in containers or use barriers to contain its roots. Deadhead spent flowers regularly to prevent self-seeding. Be vigilant about removing any unwanted seedlings that pop up.

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).

Pacific Northwest Specific Challenges: Tansy is well-suited to our mild heat, dry-summer humidity, and dry-summer rainfall. Late blight isn't a major concern for Tansy. Our cool spring soils might slow its initial growth, but once established, it's quite resilient. Slugs are not typically a problem for mature tansy plants.

Tansy makes a great companion plant in the Pacific Northwest garden. It's particularly beneficial when planted near potatoes, squash, and cucumbers, as its strong scent repels many common pests that bother these crops. The insect repellent benefits also extend to raspberries, keeping away raspberry beetles.

There aren't any significant plants to avoid planting near Tansy, but be mindful of its aggressive growth habit. Avoid planting it too close to delicate or slow-growing plants that it might outcompete.