Tansy in Zone 5A — Midwest

Tansy is a worthwhile addition to any Midwest garden, not for its flavor, but for its incredible insect-repelling properties. It's a low-maintenance plant that thrives in our fertile soil and can help protect your more sensitive crops. Plus, the bright yellow blooms add a cheerful touch to the garden all summer long.

Our Midwest weather can be unpredictable, with late frosts in spring and occasional summer heat spells. But don't worry, Tansy is a hardy plant that can handle these conditions if you time things right. With our 157-day growing season, you'll have plenty of time to establish a healthy Tansy patch.

Starting Tansy indoors isn't strictly necessary, but it can give you a head start, especially if you're eager for those insect-repelling benefits as early as possible. If you choose to go this route, start your seeds indoors from late February through mid March, about six weeks before you plan to transplant them outdoors.

Use seed trays with a good seed-starting mix, and keep them in a warm spot with plenty of light – a sunny windowsill or under grow lights works great. A little trick I like to use is bottom watering: set the tray in a shallow dish of water and let the soil soak it up from the bottom. This prevents damping-off, which can be a problem in our moderate-to-late Midwest springs.

Once the danger of frost has passed – usually sometime from mid April through mid May – it's time to transplant your Tansy seedlings outdoors. Before you plant them in the ground, you'll want to harden them off. This means gradually exposing them to outdoor conditions over about a week.

Start by putting them outside for a few hours each day in a sheltered spot, increasing the time each day. When you're ready to plant, space them 12-18 inches apart in a sunny or partially shaded spot. Keep an eye on the weather forecast – those late spring cold snaps can still happen!

Direct sowing Tansy is a straightforward option, and it works well in our Midwest climate. You can sow seeds directly into the garden from mid April through early July. Just make sure the soil has warmed up a bit, as Tansy seeds germinate best in slightly warmer soil.

Prepare the soil by loosening it and removing any weeds. Sprinkle the seeds lightly over the soil and gently press them in. Keep the soil consistently moist until the seedlings emerge. You'll want to thin the seedlings to 12-18 inches apart once they're a few inches tall. The only real con is you'll get a later start than if you started indoors.

Tansy is incredibly drought-tolerant, which is great for those of us who sometimes forget to water! Once established, it really thrives on neglect. In fact, too much water or fertilizer can actually make it *more* aggressive, which is something you want to avoid.

During our wet-summer months, you might not need to water at all, unless we're going through an unusually dry spell. The best way to tell if your Tansy needs water is to use the "finger test": stick your finger into the soil about two inches deep. If it feels dry, it's time to water. Aim for about an inch of water per week if rainfall is lacking. Water at the base of the plant rather than overhead, especially with our moderate-to-humid conditions; this helps prevent fungal diseases.

If the leaves start to droop or turn yellow, you're likely overwatering. If the leaves are crispy and brown, you're underwatering. A good layer of mulch around the base of the plants helps retain moisture and suppress weeds, which is especially helpful in our sometimes-clay soil.

Pruning Tansy is pretty simple. The main thing you want to do is deadhead the flowers. This means removing the spent blooms after they've finished flowering. This prevents the plant from self-seeding too aggressively, which is important because Tansy can be quite vigorous.

You can deadhead throughout the growing season, whenever you see faded flowers. In the fall, after the first frost around early October, cut the plant back to the ground. This will help keep it tidy and encourage new growth in the spring. Just keep in mind that Tansy can be very vigorous, so you might need to contain it with barriers to prevent it from spreading too much.

You can expect your first Tansy harvest sometime from early July through mid October, about 75 days after planting. Tansy isn't harvested for culinary purposes; in fact, it can be toxic in large amounts. Instead, you're harvesting it for its insect-repelling properties.

The best time to harvest is when the button-like yellow flowers are in full bloom, usually midsummer. Simply cut the stems near the base of the plant, being careful not to damage the remaining foliage. Tansy doesn't ripen off the vine, and it will continue to produce new growth throughout the season if you keep harvesting regularly.

As the first frost approaches in early October, you can harvest the remaining stems and dry them for use throughout the winter. Hang them upside down in a cool, dry place until they're completely dry.

Here are a couple of the most common problems you might encounter with Tansy in the Midwest:

Invasive Growth

• What it looks like: Tansy spreading beyond its intended area, popping up in unwanted places in the garden.
• What causes it: Tansy is a vigorous grower and can spread through both seeds and underground rhizomes. Our fertile soil and adequate rainfall contribute to its rapid growth.
• How to fix/prevent it: The best way to prevent Tansy from becoming invasive is to contain it. Plant it in a raised bed or surround it with barriers that extend at least 12 inches into the ground. Regularly deadhead the flowers to prevent seed dispersal.

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).

Midwest Specific Challenges: Our moderate-to-hot heat and moderate-to-humid humidity during the summer months can create ideal conditions for both rapid Tansy growth and aphid infestations. The wet-summer rainfall can also contribute to the spread of Tansy if not properly contained.

Tansy makes a good companion plant for several crops in the Midwest garden. It's known to repel certain pests, which can benefit nearby plants.

Good companions include:

• Potatoes: Tansy helps deter potato beetles.
• Squash and Cucumber: Tansy can help repel squash bugs and cucumber beetles.
• Raspberries: Tansy is thought to deter raspberry beetles.

There aren't any specific plants that are *bad* companions for Tansy, but keep in mind its vigorous growth habit. Avoid planting it too close to smaller, more delicate plants that it might overshadow or outcompete for resources.