Yarrow in Zone 6A — Great Plains

Yarrow is a fantastic addition to any Great Plains garden. Its feathery foliage and clusters of vibrant flowers bring beauty and attract beneficial insects. Plus, it’s incredibly drought-tolerant, a huge win given our variable rainfall here.

Our region definitely throws some curveballs—extreme temperature swings, occasional hail, and drying winds. But don't let that deter you. With proper timing and a little planning, you can easily grow yarrow within our 188-day growing season.

Starting yarrow indoors offers a head start, especially if you want blooms the first year. Sow seeds indoors from late January through mid February, about eight weeks before the last expected frost. Use seed trays with a good seed-starting mix, keep them warm (around 70°F), and provide plenty of light.

Bottom watering is key to prevent damping off. Since our springs can be so variable, starting indoors gives you more control over the growing environment.

Transplant your yarrow seedlings outdoors in early to late April. Harden them off for about a week beforehand, gradually exposing them to outdoor conditions. Space them 12-18 inches apart.

Keep an eye on the forecast—a late frost or sudden temperature drop can happen. If frost threatens, cover your transplants. Buying starts from a local nursery is a great way to get flowers the first year.

Direct sowing yarrow is also a viable option. Sow seeds mid April through early August. Yarrow prefers well-drained soil, so amend heavy clay with compost.

Gently press the seeds into the soil—they need light to germinate. Keep the soil consistently moist until seedlings emerge. Thin to 12-18 inches apart. Direct sowing is easier, but you might not get flowers until the second year.

Yarrow is incredibly drought-tolerant once established, making it perfect for our Plains climate. During the first few weeks after transplanting or when seedlings emerge, water regularly to help them establish strong roots. After that, you can significantly cut back.

A good rule of thumb is to check the soil moisture about two inches deep—the "finger test." If it's dry, it's time to water. Aim for about an inch of water per week during dry spells, but avoid overwatering. Water at the base of the plant to prevent fungal diseases, especially since we can get periods of low-to-moderate humidity.

Yellowing leaves can indicate overwatering, while drooping leaves signal underwatering. Mulching around the base of the plant with straw or wood chips helps retain moisture and suppress weeds, which is especially helpful during our hot summers.

Deadheading is essential for encouraging continued blooming. Simply snip off the spent flower heads throughout the growing season. This prevents the plant from putting energy into seed production and encourages more flowers.

In the fall, after the first frost around mid- October, cut the plant back to its basal foliage. Yarrow can be aggressive, so divide the plants every two to three years to prevent them from taking over your garden.

You can start harvesting yarrow flowers from mid June through late October. Harvest when the flowers are fully open and at their peak color. Cut the stems just above a leaf node.

To dry the flowers, hang them upside down in a cool, dark, and well-ventilated place. Yarrow makes an excellent dried flower arrangement. Regularly harvesting flowers encourages continued production throughout the season.

As the first frost approaches in mid- October, harvest any remaining flowers you want to dry. Even after a light frost, you can still harvest, but the quality might be slightly diminished.

Yarrow is relatively easy to grow, but here are a few common problems:

Spreads Aggressively

• What it looks like: Yarrow spreads via rhizomes (underground stems), quickly filling in garden beds and potentially encroaching on other plants.
• What causes it: Yarrow thrives in our fertile prairie soil and can be quite vigorous.
• How to fix/prevent it: Plant yarrow in a contained area or use edging to prevent spreading. Divide the plants every few years to control their size.

Powdery Mildew

• What it looks like: White or grayish powdery coating on leaves, stems. Leaves curl, yellow, and die.
• What causes it: Various fungi that thrive in warm days, cool nights, and moderate humidity. Dry leaf surfaces actually favor it.
• How to fix/prevent it: Improve air circulation through spacing and pruning. Remove affected leaves. Neem oil or potassium bicarbonate sprays help. Milk spray (1 part milk to 9 parts water) is surprisingly 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: 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.

Great Plains Specific Challenges: Our hot summers, low-to-moderate humidity, and variable rainfall can exacerbate these issues. Ensure good air circulation to prevent powdery mildew. Monitor for aphids, especially during hot, dry spells. And remember, consistent watering during establishment is crucial, but avoid overwatering once established.

Yarrow is a great companion plant for many vegetables and herbs. Plant it near tomatoes and peppers; yarrow attracts beneficial insects like ladybugs and lacewings, which prey on aphids and other pests. It also grows well near herbs, as its presence can enhance their essential oils.

Yarrow is also a good companion for strawberries, as it's thought to improve their flavor and vigor. There aren't specific plants that are bad companions for yarrow, but avoid planting it too close to plants that prefer consistently moist soil, as yarrow thrives in drier conditions.