Yarrow in Zone 6B — Great Plains

Yarrow is a workhorse in the Great Plains garden. Its feathery foliage and cheerful flowers add beauty, it attracts beneficial insects like crazy, and you can dry the blooms for long-lasting arrangements. Plus, it's tough enough to handle our intense sunshine and variable rainfall, making it a satisfying choice for any Plains gardener.

Our region's extreme weather—from sudden temperature swings to the constant wind—can be a challenge. But with smart timing and a little extra care, you can absolutely grow Yarrow successfully during our 198-day growing season.

Starting Yarrow indoors in late January through mid-February gives you a head start, especially if you want blooms the first year. This is about 8 weeks before you'd transplant outdoors. It's not essential, but can be useful.

Use seed trays with a good seed-starting mix. Keep them warm (a heat mat helps) and provide plenty of light with grow lights. Bottom watering helps prevent damping off – set the tray in a shallow pan of water until the surface looks moist. Given our variable spring, an indoor start gives young plants a fighting chance.

Transplant your Yarrow seedlings outdoors in late March through late April. Harden them off first! Give them about a week of gradual exposure to outdoor conditions. Start with an hour or two of shade and increase the time each day.

Space them 12-18 inches apart in a sunny spot with well-drained soil. Keep an eye on the weather forecast – those late-season cold snaps can still happen. Mulch around the base to retain moisture and suppress weeds. Buying starts will give you flowers the first year, but if you start from seed, expect blooms in year two.

Direct sowing Yarrow is easy and can be done early April through early August. It’s less work than starting indoors, but you won't get as early of a bloom.

Prepare a well-draining seedbed and sow seeds shallowly. Keep the soil consistently moist until seedlings emerge. Thin them to 12-18 inches apart once they have a few sets of true leaves. Keep in mind that direct-sown Yarrow may not flower in its first year but will take off the following season.

Yarrow is incredibly drought-tolerant once established, which is a huge plus for Plains gardeners dealing with our variable rainfall. The key is getting it through that first season.

During the first few weeks after planting (or after seedlings emerge), water deeply once or twice a week, providing about an inch of water each time. Use the "finger test" – stick your finger about 2 inches into the soil. If it's dry, water. After that initial period, you'll likely only need to water during extended dry spells.

Water at the base of the plant to avoid wetting the foliage, especially with our low-to-moderate humidity. Overwatering can lead to floppy growth and root rot. Yellowing leaves are a sign of overwatering; wilting leaves mean it's thirsty. A layer of mulch will help retain moisture and keep the soil cool.

Deadheading is essential for encouraging repeat blooms on Yarrow. Simply snip off the spent flower heads just below the bloom. This directs the plant's energy into producing more flowers instead of seeds.

Do this throughout the growing season whenever you see faded blooms. In late October, after the first frost, cut the plant back to its basal foliage (the leaves at the base of the plant). This helps tidy up the garden for winter and encourages fresh growth in the spring. Yarrow can be aggressive, so divide clumps every few years to keep it in check.

You can expect your first Yarrow harvest starting in mid-June, and you can continue harvesting all the way through early November. The flowers are ready to harvest when they are fully open and the color is vibrant.

Cut the stems just above a leaf node. Harvest in the morning after the dew has dried for best results. To encourage continued production, keep harvesting regularly. As the first frost approaches in late October, harvest any remaining blooms to dry indoors.

Here are the most common problems you might face with Yarrow in the Great Plains:

Spreads Aggressively

• What it looks like: Yarrow popping up where you didn't plant it, quickly forming large clumps.
• What causes it: Rhizomes (underground stems) spread rapidly, especially in fertile soil. Our long growing season can exacerbate this.
• How to fix/prevent it: Plant in a contained area or use edging to prevent spread. Divide clumps every 2-3 years to control size. Be vigilant about removing unwanted seedlings.

Powdery Mildew

• What it looks like: White or grayish powdery coating on leaves, stems. Leaves curl, yellow, and die.
• What causes it: 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. Plant resistant varieties.

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).

Great Plains Specific Challenges: The hot heat and variable rainfall can stress Yarrow, making it more susceptible to powdery mildew and aphids. The wind can also contribute to the spread of powdery mildew spores. Proper spacing and watering practices are crucial for preventing these problems.

Yarrow makes a great companion plant for many vegetables and herbs in the Great Plains garden.

It's a fantastic companion for tomatoes and peppers because it attracts beneficial insects like ladybugs and hoverflies that prey on aphids and other pests. It also does well planted near herbs like rosemary and thyme, as they share similar needs for well-drained soil and full sun. Yarrow is beneficial to strawberries because it attracts predatory wasps that control strawberry pests.

Avoid planting Yarrow near plants that prefer rich, moist soil, as Yarrow thrives in drier conditions.