Tansy in Zone 7A — Desert Southwest

Tansy is a fantastic addition to your Desert Southwest garden, not for the dinner table, but for its potent insect-repelling properties. Imagine strolling through your garden, knowing this plant is helping to keep unwanted pests away from your precious veggies, all while adding a touch of old-world charm. It's a low-water, low-maintenance champion.

Our extreme heat and alkaline soil can be tough on some plants, but Tansy is surprisingly resilient. With smart timing that makes the most of our two growing seasons and 230-day growing season, you can easily cultivate this beneficial herb.

Starting Tansy indoors in our Zone 7A Desert Southwest climate isn't essential, but it can give you a head start. If you're eager to get your plants going, sow 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 and provide warmth and bright light – a grow light is ideal. Don't forget to water from the bottom to prevent damping-off, especially important in our arid climate where seedlings can dry out quickly. Remember, our spring comes very-early, so get those seeds started!

Transplant your Tansy seedlings outdoors from mid March through early April. Before transplanting, harden them off by gradually exposing them to the outdoor environment for about a week.

Space the plants 12-18 inches apart. Keep an eye out for late frosts or unexpected temperature swings – cover your seedlings if necessary.

Direct sowing Tansy is a simple and effective method in the Desert Southwest. You can sow seeds directly into the garden from mid March through mid August.

Prepare the soil by loosening it and removing any rocks or debris. Tansy isn't picky, but well-draining soil is always best. Sow the seeds shallowly and keep the soil consistently moist until they germinate. Remember to thin seedlings to 12-18 inches apart.

Tansy thrives on neglect, which is great news for us Desert Southwest gardeners dealing with water scarcity. During the intense heat of summer, water deeply but infrequently, usually about once every 1-2 weeks, giving them about 1 inch of water. Let the top 2 inches of soil dry out between waterings – use the finger test to check.

During the monsoon season, rely on the rainfall to do most of the work. Water at the base of the plant to avoid wetting the foliage, which can encourage fungal diseases in our arid environment. Yellowing leaves can indicate overwatering, while wilting suggests underwatering.

A layer of gravel mulch can help retain moisture and protect the soil from the intense sun.

Pruning Tansy is crucial for maintaining its vigor and preventing it from becoming too aggressive in your Desert Southwest garden. Deadhead spent flowers regularly throughout the growing season to prevent self-seeding.

In late fall, after the first frost around early November, cut the plant back to a few inches above the ground. This encourages new growth in the spring.

You can expect your first harvest of Tansy starting late May through mid November, about 75 days after planting. While Tansy isn't for eating, it's used for its insect-repelling properties.

Harvest the leaves and flowers when the button-like yellow flowers are in full bloom during midsummer. Cut the stems carefully to avoid damaging the plant.

Harvesting regularly encourages continued production. As the first frost approaches in early November, you can still harvest the remaining foliage for use in pest control.

Here are a couple of common problems you might encounter with Tansy in our Desert Southwest gardens:

Invasive Nature

• What it looks like: Tansy spreading rapidly beyond its intended area, crowding out other plants.
• What causes it: Tansy is a vigorous grower and self-seeder. In our long growing season, it can quickly become invasive if not managed.
• How to fix/prevent it: Plant Tansy in containers or use underground barriers to contain its roots. Deadhead flowers regularly to prevent seed dispersal. Remove unwanted seedlings promptly.

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).

Desert Southwest Specific Challenges: The extreme heat and arid humidity of the Desert Southwest can stress Tansy, making it more susceptible to pests like aphids. Monitor your plants regularly and provide adequate water to keep them healthy and resilient.

Tansy makes a great companion plant for several vegetables in the Desert Southwest. It helps repel pests from potatoes, squash, and cucumbers, protecting them from common garden invaders.

Raspberries also benefit from Tansy's presence as a pest deterrent. Avoid planting Tansy near brassicas like cabbage and broccoli, as it can inhibit their growth.