Yarrow in Zone 5A — Midwest

Yarrow is a fantastic addition to any Midwest garden. Its feathery foliage and cheerful blooms add beauty, and it's incredibly versatile. Plus, Yarrow thrives in our fertile soil and provides a long season of color, attracting beneficial insects to your garden.

While Midwest weather can be unpredictable, especially with those summer heat spells and the occasional tornado, Yarrow is a hardy perennial. With a little planning around our 157-day growing season, you can enjoy its beauty year after year.

Starting Yarrow indoors gives you a head start, but it's not always necessary. If you're aiming for blooms in the first year or want a specific variety, indoor starting is a good option.

Start your seeds indoors from mid February through early March, about eight weeks before you plan to transplant. Use seed trays with a good seed-starting mix, provide warmth, and ensure they get plenty of light. Bottom watering helps prevent damping off and keeps the seedlings happy. Remember our springs can be moderate-to-late, so don't rush the transplanting process.

Transplanting Yarrow outdoors is best done from mid April through mid May, after the danger of hard frost has passed. Before planting, harden off your seedlings by gradually exposing them to outdoor conditions for about a week.

Choose a sunny spot and space your Yarrow plants 12-18 inches apart. Keep an eye on the weather forecast; we sometimes get late frosts in the Midwest, so be prepared to cover your transplants if needed. Since it's a perennial, buying starts can give you flowers the first year, which is a nice bonus.

Direct sowing Yarrow is a simple and effective method, especially if you're not in a hurry for blooms. Sow seeds from early May through mid July, ensuring the soil has warmed up a bit.

Prepare the soil by loosening it and removing any weeds. Sprinkle the seeds lightly on the surface and gently press them in. Keep the soil consistently moist until germination. Thin seedlings to 12-18 inches apart as they grow. The downside is you'll likely wait until the following year for significant flowering.

Yarrow is wonderfully drought-tolerant once established, making it a low-maintenance choice for Midwest gardens. However, proper watering is still important, especially during the first few weeks after planting and during those summer heat spells.

During the initial establishment period, water regularly to keep the soil consistently moist. After that, let the soil dry out between waterings. Use the "finger test" – stick your finger about two inches deep into the soil; if it's dry, it's time to water. Aim for about an inch of water per week, either from rainfall or irrigation. Water at the base of the plant to avoid wetting the foliage, which can increase the risk of fungal diseases in our moderate-to-humid climate.

Signs of underwatering include wilting leaves, while overwatering can lead to floppy growth and root rot. A light layer of mulch around the base of the plant can help retain moisture and suppress weeds, which is helpful given our wet-summer rainfall patterns.

Pruning Yarrow is easy and helps encourage more blooms and maintain its shape. Deadhead spent flowers throughout the growing season to promote a second flush of blooms. Simply snip off the faded flower heads just below the bloom.

In the fall, after the first frost around early October in the Midwest, 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 overcrowding.

You can expect your first Yarrow harvest from early July through mid October, depending on when you planted. The flowers are ready to harvest when they are fully open and the petals are vibrant.

Cut the flower stems in the morning after the dew has dried. To encourage continued production, cut the stems just above a set of leaves. Yarrow is an excellent dried flower, so hang the stems upside down in a cool, dark, and dry place to dry them. As the first frost approaches in early October in the Midwest, harvest any remaining blooms to dry and enjoy indoors. Yarrow also attracts many beneficial insects to your garden, so leaving some flowers for them is a great idea.

Here are three common problems you might encounter with Yarrow in the Midwest:

Aggressive Spreading

• What it looks like: Yarrow spreads via rhizomes (underground stems), quickly forming dense clumps. It can pop up in unwanted areas of your garden.
• What causes it: Our fertile soil and adequate rainfall in the Midwest provide ideal conditions for Yarrow to spread vigorously.
• How to fix/prevent it: Plant Yarrow in a contained area or use edging to prevent it from spreading. Divide the clumps every 2-3 years to control its size. Be diligent about removing unwanted shoots as they appear.

Powdery Mildew

• What it looks like: White or grayish powdery coating on leaves, stems, and sometimes fruit. Leaves curl, yellow, and die. Reduces plant vigor.
• What causes it: Various fungi that thrive in warm days, cool nights, and moderate humidity. Dry leaf surfaces actually favor it (unlike most fungi). Midwest's moderate-to-humid summers can create favorable conditions.
• 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. Midwest's summer heat spells can lead to aphid outbreaks.
• 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: The moderate-to-hot heat and moderate-to-humid humidity in the Midwest can create conditions favorable for powdery mildew and aphid infestations. The wet-summer rainfall can also contribute to the spread of fungal diseases. Regular monitoring and proactive measures are key to keeping your Yarrow healthy and thriving.

Yarrow is a great companion plant in the Midwest garden, attracting beneficial insects that help control pests and improve pollination. It particularly benefits tomatoes and peppers by attracting predatory wasps that feed on tomato hornworms and aphids.

Yarrow also makes a good companion for herbs, enhancing their essential oil production and attracting pollinators. Strawberries also benefit from Yarrow's presence, as it attracts hoverflies that prey on strawberry aphids. I'd avoid planting it near brassicas like cabbage or broccoli, as it might attract cabbage moths.