Tansy in Zone 7A — Pacific Northwest

Tansy is a worthwhile addition to your Pacific Northwest garden. Its insect-repelling properties make it a valuable companion plant, helping protect your more vulnerable crops. Plus, the bright yellow flowers add a cheerful touch to your garden through our long, mild fall.

While we PNW gardeners sometimes struggle with cool soil in spring and the occasional late blight, these challenges are easily managed with proper timing and care. With our 183-day growing season, you'll find plenty of time to enjoy a flourishing Tansy patch.

Starting Tansy indoors in the PNW can give you a head start, though it's not essential. If you're eager to get things going, aim to start your seeds from mid-February through early March, roughly six weeks before you plan to transplant.

Use seed trays with a good seed-starting mix and provide consistent warmth and light. Bottom watering is helpful to prevent damping-off, especially with our often overcast spring days.

Transplant your Tansy seedlings outdoors from early April through early May, once the risk of hard frost has passed. Before planting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week.

Space the 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 time.

Direct sowing Tansy is a straightforward method that works well in our climate. Sow seeds directly into the garden from early April through late July.

Ensure the soil is prepared and has warmed up a bit – Tansy isn't a huge fan of cool soil. Space the seeds according to the 12-18 inch recommendation, and keep the soil consistently moist until germination.

Tansy is very drought-tolerant and thrives on neglect, making it an excellent choice for our dry summer months in the Pacific Northwest. Once established, it needs very little supplemental watering.

During our wet springs, you likely won't need to water at all. In the drier summer months, check the soil moisture by using the finger test: stick your finger about 2 inches deep into the soil. If it feels dry, give the plants a good soak, aiming for about 1 inch of water per week. Water at the base of the plant to avoid creating overly humid conditions, which can encourage fungal diseases.

Signs of underwatering include wilting or drooping leaves, while yellowing leaves can indicate overwatering. A layer of mulch around the base of the plants can help retain moisture and reduce the need for frequent watering.

Pruning Tansy is fairly simple and mostly involves deadheading. Remove the spent flowers regularly throughout the growing season to prevent aggressive self-seeding – this plant can be quite vigorous!

You can cut back the entire plant in the fall after the first frost around mid-October to tidy up the garden. Be mindful of its vigorous nature and consider containing it if you don't want it spreading.

You can expect your first harvest of Tansy from mid-June through late October, about 75 days after planting. The plant is ready when the button-like yellow flowers are in full bloom.

Harvest by snipping off the flower heads or stems as needed. Keep in mind that Tansy is primarily used as an insect repellent and not for culinary purposes, as it can be toxic in large amounts. Regular harvesting encourages continued production throughout our long, mild fall. As the first frost approaches, you can harvest the remaining foliage and dry it for winter use.

Tansy is generally a low-maintenance plant, but here are a couple of potential problems to watch out for in the Pacific Northwest:

Invasive tendencies

• What it looks like: Tansy spreading beyond its intended area, popping up in unwanted parts of the garden.
• What causes it: Tansy is a vigorous self-seeder and can quickly become invasive if not properly managed.
• How to fix/prevent it: Deadhead spent flowers regularly to prevent seed formation. Consider planting Tansy in containers or using barriers to contain its spread.

Aphids

• What it looks like: Clusters of tiny green, black, or white insects on stems and leaf undersides. You might also see sticky honeydew residue or curled, distorted new growth.
• What causes it: Aphids are sap-sucking insects that thrive in warm weather. Ant colonies may farm them for honeydew.
• How to fix/prevent it: A strong spray of water can knock aphids off the plant. Encourage natural predators like ladybugs and lacewings. For heavy infestations, use insecticidal soap or neem oil. Avoid over-fertilizing with nitrogen, which attracts aphids.

Pacific Northwest Specific Challenges: Our mild heat and dry-summer rainfall actually benefit Tansy, as it prefers drier conditions and isn't as susceptible to fungal diseases that plague other plants in wetter climates. However, keep an eye out for aphids, especially during warmer spells.

Tansy makes a great companion plant for several crops in the Pacific Northwest garden. It's known to repel certain insects, benefiting plants like:

• Potatoes: Tansy can help deter potato beetles.
• Squash: It may repel squash bugs and vine borers.
• Cucumbers: Tansy can help keep cucumber beetles away.
• Raspberries: It can deter certain raspberry pests.

Avoid planting Tansy near plants that might be negatively affected by its strong aroma or allelopathic properties. As a general rule, observe how your plants interact and adjust accordingly.