Tansy in Zone 6A — Pacific Northwest

Tansy is a fantastic addition to any Pacific Northwest garden. Its insect-repelling properties make it a valuable companion plant. Plus, the vibrant yellow flowers are a welcome sight in our mild summers, adding brightness even on overcast spring days.

While we might struggle with heat-loving plants due to our relatively short summers, Tansy thrives here. Our 148-day growing season gives you plenty of time to establish a healthy, productive plant. Timing is key in our climate, but with a little planning, you'll have no problem growing Tansy.

Starting Tansy indoors isn't strictly necessary in our climate, but it can give you a head start. If you're aiming for the earliest possible blooms, start seeds indoors from early to late March, about six weeks before you plan to transplant. Use seed trays with a good seed-starting mix, and provide warmth and light.

Bottom watering is especially helpful at this stage to prevent damping off. Place the tray in a shallow dish of water and let the soil absorb moisture from the bottom. Remember that our springs can be slow to warm up, so giving your seedlings a head start indoors can be beneficial.

Transplant your Tansy seedlings outdoors from late April through late 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 sun and wind.

Space plants 12-18 inches apart to allow for their clumping growth habit. Keep an eye on the weather forecast, as we can still get unexpected cold snaps during this period. Protect young plants with row covers if necessary.

Direct sowing Tansy is an easy option in our climate. Sow seeds directly into the garden from late April through early July. Choose a spot with full sun to part shade.

Prepare the soil by loosening it and removing any weeds. Tansy isn't fussy about soil, but good drainage is always a plus. Space seeds 12-18 inches apart, or thin seedlings to that spacing once they emerge.

Tansy is very drought-tolerant and thrives on neglect, which is great for our dry summer months in the Pacific Northwest. In fact, too much water or fertilizer can make it even more aggressive.

During our wet springs, you likely won't need to water at all. Once the dry summer months arrive, check the soil moisture with the "finger test." Stick your finger about two inches into the soil. If it feels dry, it's time to water. Aim for about an inch of water per week during dry spells. Watering at the base of the plant is preferable to overhead watering, especially during our dry summers, as it helps prevent fungal diseases.

Signs of underwatering include wilting leaves, while overwatering can lead to yellowing leaves and root rot. A layer of mulch around the base of the plant can help retain moisture and suppress weeds, especially during our drier months.

Deadheading is key to managing Tansy, as it helps prevent aggressive self-seeding. Snip off spent flower heads regularly throughout the growing season. This encourages more blooms and keeps the plant tidy.

In the fall, after the first frost around early October, cut back the entire plant to near ground level. This helps it overwinter successfully and promotes vigorous growth in the spring. Because Tansy is vigorous, consider containing it with barriers to prevent it from spreading too much.

You can expect your first harvest of Tansy from early July through mid-October, about 75 days after planting. The button-like yellow flowers will be in full bloom midsummer, indicating they're ready for harvest. Tansy is primarily used as an insect repellent, not for culinary purposes, as it can be toxic in large amounts.

To harvest, simply cut the stems with flowers. Harvest regularly to encourage continued production. As the first frost approaches in early October, you can harvest the remaining stems and dry them for later use. Hang them upside down in a cool, dry place until they are completely dry.

Here are a couple of common problems you might encounter with Tansy in the Pacific Northwest:

Invasive Tendencies *What it looks like:* Tansy spreads rapidly, forming dense clumps and potentially overtaking other plants in your garden. *What causes it:* Tansy is a vigorous grower and readily self-seeds. Our mild summers and long growing season allow it to thrive and spread quickly. *How to fix/prevent it:* Contain Tansy by planting it in a pot or surrounding it with barriers buried at least 12 inches deep. Deadhead regularly to prevent seed formation. Remove unwanted seedlings promptly.

Aphids *What it looks like:* Clusters of tiny soft-bodied insects (green, black, or white) on stems and leaf undersides. You may also see a sticky honeydew residue and curled or distorted new growth. *What causes it:* Aphids are rapid-reproducing sap-sucking insects. Populations explode in warm weather. Ant colonies may farm them for honeydew. *How to fix/prevent it:* A strong spray of water can knock them off. Encourage ladybugs and lacewings (natural predators). Use insecticidal soap for heavy infestations, or neem oil for a systemic approach. Avoid excess nitrogen fertilizer, as it attracts them.

Pacific Northwest Specific Challenges: Our mild heat and dry-summer rainfall actually benefit Tansy, making it less susceptible to fungal diseases that thrive in humid climates. However, its vigor means you need to be vigilant about containing it.

Tansy makes a great companion plant for several crops in the Pacific Northwest. It repels certain pests, benefiting nearby plants.

Good companions include:

• Potato: Tansy repels potato beetles, a common pest in our region.
• Squash & Cucumber: Tansy can deter squash bugs and cucumber beetles.
• Raspberry: Tansy deters raspberry beetles.

There are no known bad companions for Tansy.