Tansy in Zone 8B — Northern California

Tansy is a fantastic, low-maintenance addition to any Northern California garden. It thrives in our Mediterranean climate and offers a natural way to deter pests from your precious veggies. Plus, those cheerful yellow button flowers add a pop of color to your landscape.

While we face challenges like drought and increasingly dry summers, Tansy is well-suited to handle them. Our long growing season (around 269 days!) gives you plenty of time to get it established and enjoy its benefits.

Starting Tansy indoors is an option, but honestly, it's not really necessary in our climate. If you're itching to get a head start, you can start seeds indoors from late December through mid January, about six weeks before our typical transplanting window.

Use seed trays with a good seed-starting mix, and keep them warm (around 70°F) and under grow lights. Bottom watering helps prevent damping-off, so set the tray in a shallow dish of water and let the soil soak it up from the bottom. In Northern California, with our early springs, you might find direct sowing is easier and just as effective.

If you started your Tansy indoors, transplant it outdoors from mid February through mid March. Before you do, harden off the seedlings by gradually exposing them to outdoor conditions for about a week. This prevents shock.

Space the plants 12-18 inches apart in a sunny spot. Keep an eye on the weather forecast – even though our winters are mild, we can still get late frosts around this time, so be ready to cover your seedlings if needed.

Direct sowing Tansy is a breeze here in Northern California, and honestly, my preferred method. You can sow seeds directly into the garden from mid February through late August.

Choose a sunny spot with well-drained soil. Lightly rake the soil, scatter the seeds, and gently press them in. Keep the soil consistently moist until the seedlings emerge. Thin the seedlings to 12-18 inches apart once they're a few inches tall.

Tansy is a champ when it comes to drought tolerance, which is a huge plus in our Northern California climate! Once established, it really thrives on neglect. Overwatering is a bigger problem than underwatering.

During our dry summers, water deeply but infrequently – about once every 2-3 weeks. Use the finger test: stick your finger about 2 inches into the soil. If it's dry, it's time to water. Aim for about 1 inch of water per week when you do water. Given our low humidity, watering at the base of the plant is fine, but overhead watering in the morning is okay too.

Yellowing leaves are a sign of overwatering, while drooping leaves mean it's thirsty. A good layer of mulch around the base of the plants helps retain moisture and suppress weeds, which is especially helpful during our dry summers and fire season.

To keep your Tansy plant tidy and prevent it from taking over your garden, regular pruning is key. Deadhead the flowers as they fade to prevent self-seeding. This is especially important if you don't want it spreading everywhere!

Throughout the growing season, you can trim back any stems that get too leggy or unruly. After the first frost, usually around late November in Northern California, cut the plant back to a few inches above the ground. It will bounce back in the spring.

You can start harvesting Tansy from early May through early December. The best time to harvest is when the button-like yellow flowers are in full bloom, usually in midsummer.

Cut the stems close to the base of the plant, using sharp pruners or scissors. Remember, Tansy is primarily used as an insect repellent, not for culinary purposes, as it can be toxic in large amounts. Harvesting regularly encourages continued production throughout our long growing season. Even as the first frost approaches in late November, you can still harvest stems for use indoors.

Here are a couple of common problems you might encounter with Tansy in Northern California:

Invasive Spread *What it looks like:* Seedlings popping up everywhere you don't want them. *What causes it:* Tansy is a vigorous self-seeder, and the seeds can spread easily. Our mild winters mean more seeds survive to germinate. *How to fix/prevent it:* Deadhead flowers religiously before they go to seed. Consider planting Tansy in a container to restrict its spread. You can also use barriers in the ground to contain the roots.

Aphids *What it looks like:* Clusters of tiny green, black, or white insects on stems and undersides of leaves. Sticky honeydew residue. Curled or distorted new growth. *What causes it:* Aphids are rapid-reproducing sap-sucking insects. Populations explode during warm spells. Ant colonies may farm them for honeydew. *How to fix/prevent it:* A strong spray of water from the hose can knock them off. Encourage beneficial insects like ladybugs and lacewings. Insecticidal soap works well, and neem oil can be used for heavier infestations. Avoid over-fertilizing with nitrogen, as this attracts aphids.

Northern California Specific Challenges: Our moderate-to-hot summers, combined with low humidity and dry conditions, can stress plants, making them more susceptible to pests. Be vigilant about watering and providing adequate shade during the hottest part of the day to keep your Tansy healthy.

Tansy makes a great companion plant for several crops in your Northern California garden. It's known to repel certain pests, benefiting plants like potatoes, squash, and cucumbers. Plant it near raspberries to deter raspberry beetles.

Avoid planting Tansy near brassicas like cabbage or broccoli, as it can attract cabbage moths. Keep it away from herbs like mint, as they can compete for resources.