Yarrow in Zone 6B — Midwest

Yarrow is a fantastic addition to any Midwest garden. Its feathery foliage and clusters of blooms add beauty, but it's also a magnet for beneficial insects like ladybugs and pollinators, helping your whole garden thrive. Plus, yarrow is incredibly versatile – use it in fresh bouquets, dried arrangements, or even as a medicinal herb.

While our Midwest weather can be unpredictable with its variable spring and summer heat spells, yarrow is tough enough to handle it. Its long bloom time, from mid-June through late October, means you'll get plenty of enjoyment out of it during our 183-day growing season.

Starting yarrow indoors in the Midwest is an option, especially if you're after specific cultivars or want a head start. Begin in late January through mid February, about eight weeks before you plan to transplant. You'll need seed trays, a good seed-starting mix, and a warm spot – a heat mat can help with germination.

Make sure to provide plenty of light; a grow light is best, as our late start to spring means natural light can be inconsistent. Bottom water your seedlings to prevent damping off and encourage strong root growth. Transplanting gives you a jump on our moderate-to-late spring.

Transplanting yarrow outdoors in the Midwest should be done in early to late April. Before you move your seedlings outside permanently, harden them off for about a week. Gradually expose them to outdoor conditions, starting with an hour or two of shade and increasing the time and sun exposure each day.

Plant your yarrow seedlings 12-18 inches apart in a sunny spot. Keep an eye on the weather forecast, as we can still get a late frost in April. If frost is predicted, cover your young plants with a frost blanket or cloche. Since yarrow is a perennial, buying starts can give you blooms in the first year.

Direct sowing yarrow is a simple option for Midwest gardeners. Wait until mid April through late July when the soil has warmed up a bit. Choose a sunny location with well-drained soil. Yarrow isn't picky about soil fertility, but it does need good drainage, especially in our wet-summer climate.

Prepare the soil by loosening it and removing any weeds. Sow the seeds shallowly and keep the soil consistently moist until germination. Once the seedlings emerge, thin them to 12-18 inches apart. Direct sowing can be slower to establish than transplants, but it's a low-effort way to add yarrow to your garden.

Yarrow is incredibly drought-tolerant once established, which is a huge plus for Midwest gardeners dealing with those summer heat spells. However, it's important to get the watering right, especially in our moderate-to-humid climate. Overwatering can lead to floppy growth and root rot.

During the first few weeks after planting, water regularly to help the plants establish a strong root system. After that, water only when the top two inches of soil feel dry to the touch – use the finger test. In general, established yarrow needs about an inch of water per week, including rainfall.

Water at the base of the plants to avoid wetting the foliage, which can encourage fungal diseases in our humid summers. Mulching around the plants with a layer of compost or shredded bark will help retain moisture and suppress weeds. Watch for signs of under or overwatering: wilting leaves indicate a need for water, while yellowing leaves or mushy stems suggest overwatering.

Pruning yarrow is straightforward and helps keep it looking its best. Deadhead spent flowers regularly throughout the growing season to encourage more blooms. Simply snip off the flower heads just below the lowest set of leaves. This encourages the plant to put its energy into producing new flowers rather than seeds.

In the fall, after the first frost around mid- October, cut the plant back to its basal foliage. This helps tidy up the garden and prepares the plant for winter dormancy. Yarrow can be aggressive, so divide the clumps every 2-3 years to prevent them from taking over.

You can expect your first yarrow harvest in the Midwest from mid June through late October, about 65 days after planting. Harvest flowers for drying when they are fully open and their color is at its peak. Cut the stems long, leaving enough foliage on the plant to continue growing.

To dry yarrow, bundle the stems together and hang them upside down in a cool, dark, and well-ventilated place. Once the flowers are dry, you can use them in dried arrangements, potpourri, or herbal remedies. Regular harvesting encourages continued production of blooms throughout the season.

As the first frost approaches in mid- October, harvest any remaining flowers that are still in good condition. Even if they don't dry perfectly, they can still be used in fresh bouquets or as a colorful addition to your compost pile.

Here are the top 3 problems you might encounter growing yarrow in the Midwest:

Aggressive Spreading

• What it looks like: Yarrow quickly expands beyond its intended area, crowding out other plants.
• What causes it: Yarrow spreads through rhizomes (underground stems), which can be quite vigorous in our fertile soil.
• How to fix/prevent it: Plant yarrow in a contained area, such as a raised bed or surrounded by edging. Divide the plants every 2-3 years to control their spread. Be vigilant about removing unwanted shoots as they appear.

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 – conditions we often experience in the Midwest. Dry leaf surfaces actually favor it.
• How to fix/prevent it: Improve air circulation by spacing plants adequately and pruning. Remove affected leaves promptly. Neem oil or potassium bicarbonate sprays can help. Milk spray (1 part milk to 9 parts water) is also effective. Plant resistant varieties when possible.

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, which we certainly get in the Midwest. Ant colonies may farm them for honeydew.
• How to fix/prevent it: A strong water spray can knock them off. Encourage ladybugs and lacewings (natural predators). Insecticidal soap can be used for heavy infestations. Neem oil works systemically. Avoid excess nitrogen fertilizer, as it attracts them.

Midwest Specific Challenges: The moderate-to-hot heat and moderate-to-humid conditions of our Midwest summers can create a breeding ground for powdery mildew and aphid infestations. Our wet-summer rainfall, combined with clay soil in many areas, can also lead to root rot if drainage isn't adequate. Be sure to provide good air circulation, well-drained soil, and monitor your plants regularly for signs of pests or diseases.

Yarrow makes a great companion plant for many vegetables and herbs in the Midwest garden. Plant it near tomatoes and peppers to attract beneficial insects like ladybugs and lacewings, which will help control pests like aphids. Yarrow also benefits herbs like rosemary and thyme by improving their growth and flavor.

Strawberries also benefit from yarrow nearby, as it helps deter pests and attract pollinators, leading to increased fruit production. Avoid planting yarrow near brassicas (cabbage, broccoli, kale), as it can attract cabbage moths.