Yarrow in Zone 7A — Midwest

Yarrow is a workhorse in the Midwest garden. Its feathery foliage and clusters of blooms add beauty, and the flowers are fantastic dried. Plus, it's a magnet for beneficial insects, which is a win for the whole garden! The fertile soil and adequate rainfall we often get here in Zone 7A means yarrow thrives.

Midwest weather can be unpredictable, with cold winters and variable springs. But yarrow is hardy and adaptable. Our 193-day growing season gives you plenty of time to get a good harvest. With a little planning, you can enjoy its beauty and benefits.

Starting yarrow indoors gives you a head start, but it's not essential, since you can direct sow. If you want blooms the first year, especially with named varieties, starting indoors is a good idea. Start seeds late January through mid February, about 8 weeks before you want to transplant.

Use seed trays or small pots with a good seed-starting mix. Keep them warm (around 70°F) and provide plenty of light with grow lights. Bottom watering helps prevent damping off. Given our moderate-to-late spring here in the Midwest, this timing gives you strong transplants ready to go out after the last frost.

Transplant your yarrow seedlings outdoors late March through late April. Before planting, harden them off by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the Midwest weather.

Choose a sunny spot with well-drained soil. Space the plants 12-18 inches apart to give them room to spread. Keep an eye on the weather forecast – we can still get a late frost in the Midwest, so be ready to cover your seedlings if needed. Buying starts is also an option, especially to ensure flowers in the first year, as yarrow is a perennial.

Direct sowing yarrow is a simple option, especially if you're growing it as a ground cover or for its foliage. Sow seeds early April through early August. Yarrow needs light to germinate, so don't bury the seeds too deeply – just press them lightly into the soil.

Make sure the soil is relatively warm, at least 60°F, for best germination. Keep the soil consistently moist until the seedlings emerge. Thin the seedlings to 12-18 inches apart once they're a few inches tall. The downside to direct sowing is that you likely won't get flowers until the second year.

Yarrow is very drought-tolerant once established, which is great for those summer heat spells we get in the Midwest. In its first year, however, it will need more regular watering. A good rule of thumb is to water deeply when the top 2 inches of soil feel dry to the touch – the "finger test."

During the hotter, drier parts of summer, aim for about 1 inch of water per week, either from rainfall or irrigation. Water at the base of the plant to avoid wetting the foliage, which can encourage fungal diseases in our moderate-to-humid summers. Signs of underwatering include wilting or yellowing leaves. Overwatering can lead to floppy growth and root rot.

A layer of mulch around the base of the plants helps retain moisture and suppress weeds, but be sure to keep it away from the stems to prevent rot. Given our wet-summer rainfall patterns, make sure your yarrow is planted in well-draining soil to avoid problems.

Deadheading is key to keeping your yarrow blooming throughout the season. Simply snip off the spent flower heads as they fade. This encourages the plant to produce more flowers.

You can deadhead anytime from mid June through late October as the flowers fade. In the fall, after the first frost around mid- October, cut the plant back to its basal foliage (the leaves at the base of the plant). This helps keep it tidy over the winter. Yarrow can be aggressive, so divide the clumps every 2-3 years to keep it under control.

You can expect your first yarrow harvest starting mid June through late October, about 65 days after planting. Harvest the flowers for drying when they are fully open and their color is at its peak. These make excellent dried flowers.

Cut the stems just above a leaf node, using sharp scissors or pruners. Hang the stems upside down in a cool, dark, dry place to dry them. Regular harvesting encourages the plant to produce more flowers throughout the season. As the first frost approaches in mid- October, harvest any remaining flowers you want to dry.

Here are three common problems you might encounter growing yarrow in the Midwest:

Spreads Aggressively

• What it looks like: Yarrow can spread quickly via rhizomes (underground stems), forming dense clumps and potentially overtaking other plants.
• What causes it: Our fertile soil and adequate rainfall help yarrow thrive, but also contribute to its aggressive growth habit.
• How to fix/prevent it: Plant yarrow in a contained area, such as a raised bed or surrounded by edging. Divide the plant every 2-3 years to control its spread. Be vigilant about removing unwanted shoots.

Powdery Mildew

• What it looks like: White or grayish powdery coating on leaves, stems, and sometimes flower heads. Leaves may curl, yellow, and die.
• What causes it: Powdery mildew thrives in warm days, cool nights, and moderate humidity, which we often experience in the Midwest. It's also favored by dry leaf surfaces.
• How to fix/prevent it: Improve air circulation by spacing plants adequately and pruning as needed. Remove affected leaves promptly. Neem oil or potassium bicarbonate sprays can help. A milk spray (1 part milk to 9 parts water) can also be effective.

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: Aphids are sap-sucking insects that reproduce rapidly, especially in warm weather. Ant colonies often farm them for their honeydew.
• How to fix/prevent it: Knock aphids off plants with a strong spray of water. Encourage ladybugs and lacewings, which are natural predators. Use insecticidal soap for heavy infestations. Neem oil also works. Avoid excess nitrogen fertilizer, as it attracts aphids.

Midwest Specific Challenges: The moderate-to-hot heat and moderate-to-humid humidity in the Midwest can create favorable conditions for powdery mildew and aphid infestations. Regular monitoring and proactive measures are key to keeping your yarrow healthy. Be sure to provide good air circulation and avoid overwatering.

Yarrow makes a great companion plant for many vegetables and herbs in the Midwest garden. It attracts beneficial insects like ladybugs and hoverflies, which prey on pests like aphids and caterpillars.

Good companions include tomatoes and peppers, as the beneficial insects yarrow attracts will help protect these crops from pests. Yarrow also pairs well with herbs like rosemary and thyme. It's also said to improve the flavor of strawberries when planted nearby. Avoid planting yarrow near brassicas like cabbage and broccoli, as it can attract cabbage moths.