Yarrow in Zone 5B — Midwest

Yarrow is a fantastic addition to any Midwest garden. Its feathery foliage and clusters of bright flowers add beauty and attract beneficial insects. Plus, it's incredibly versatile – use it in dried arrangements, as a medicinal herb, or simply enjoy its beauty in your borders. The satisfaction of growing a plant that thrives despite our variable Midwest weather is hard to beat!

While our region offers fertile soil and adequate rainfall, we also face cold winters, temperature swings in spring, and the occasional summer heat spells. Luckily, Yarrow is a tough plant, and with a little planning, you can easily incorporate it into your 168-day growing season. Timing is key for success in our 5B zone.

Starting Yarrow indoors is definitely an option, especially if you're after a specific variety or want blooms the first year. You'll want to sow those tiny seeds sometime in early to late February, about 8 weeks before you plan to transplant. Use seed trays with a good seed-starting mix, and keep them warm (around 70°F) under grow lights.

Bottom watering is your friend here – it helps prevent damping-off and keeps the soil evenly moist. Remember that our spring can be moderate-to-late in the Midwest, so be prepared to adjust your transplanting schedule if we get a late cold snap.

Once the danger of frost has passed – typically mid April through early May around here – it's time to get your Yarrow seedlings into the ground. Before you do, harden them off by gradually exposing them to outdoor conditions for about a week. This helps them adjust to the sun and wind.

Plant them 12-18 inches apart in a sunny spot with well-drained soil. Keep an eye on the weather forecast; we sometimes get unexpected cold snaps even in late spring. If you're after flowers the first year, you may want to consider buying starts from a local nursery.

Direct sowing Yarrow is a perfectly viable option, and it saves you the hassle of starting seeds indoors. Wait until the soil has warmed up a bit, usually late April through late July. Prepare the soil by loosening it and removing any weeds.

Sprinkle the seeds lightly on the surface and gently press them into the soil. Keep the soil consistently moist until the seedlings emerge. Once they're a few inches tall, thin them to 12-18 inches apart.

Yarrow is incredibly drought-tolerant once established, which is great news for us Midwest gardeners! Our summers can bring moderate-to-hot heat and moderate-to-humid humidity, but we also get our fair share of wet-summer rainfall (30-40 inches annually). So, it's all about finding the right balance.

In the spring, water regularly until the plants are established. Once they're growing well, you can ease up on the watering. A good rule of thumb is to check the soil about 2 inches deep – if it's dry, it's time to water. Usually, about an inch of water per week is plenty, even during our summer heat spells. Water at the base of the plant to avoid wetting the foliage, especially with our moderate-to-humid conditions; this helps prevent fungal diseases.

Signs of underwatering include wilting leaves and stunted growth. Overwatering, on the other hand, can lead to floppy growth and root rot. Adding a layer of mulch around your plants helps retain moisture and suppress weeds, which is always a bonus in the Midwest!

Pruning Yarrow is pretty straightforward. The main thing you'll want to do is deadhead the spent flowers. This encourages the plant to produce more blooms throughout the season. Simply snip off the faded flower heads just below the next set of leaves.

You can deadhead anytime from late June through mid October. In the fall, after the first frost around early October, cut the plant back to its basal foliage (the leaves at the base of the plant). Yarrow can be a bit aggressive, so you might need to divide it every 2-3 years to keep it in check.

You can expect your first harvest of Yarrow flowers sometime in late June through mid October, about 65 days after planting. The best time to harvest is when the flowers are fully open and at their peak color. These make excellent dried flowers!

To harvest, simply cut the stems just above a set of leaves. You can bunch them together and hang them upside down in a cool, dark, and dry place to dry. Regular harvesting encourages the plant to produce more flowers, so keep at it throughout the season.

As the first frost approaches in early October, harvest any remaining flowers you want to dry. Even after a light frost, the foliage still looks attractive.

Yarrow is generally a tough plant, but here are a few common problems you might encounter in the Midwest:

Aggressive Spreading

• What it looks like: Yarrow can spread quickly via rhizomes, potentially taking over garden beds.
• What causes it: Our fertile soil and adequate rainfall can fuel its growth.
• How to fix/prevent it: Plant in contained beds or use root barriers. Divide clumps every few years to manage size. Remove unwanted shoots promptly.

Powdery Mildew

• What it looks like: White or grayish powdery coating on leaves, stems, and sometimes fruit. Leaves curl, yellow, and die.
• What causes it: Various fungi that thrive in warm days, cool nights, and moderate humidity – common conditions in the Midwest. Dry leaf surfaces 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).

Midwest Specific Challenges: Our moderate-to-hot heat and moderate-to-humid humidity during the summer months can create favorable conditions for powdery mildew and aphid infestations. Be vigilant about monitoring your plants and take action promptly to prevent these problems from getting out of hand. And be sure to manage the spread if you don't want Yarrow taking over.

Yarrow is a great companion plant for many vegetables and herbs in the Midwest garden. It attracts beneficial insects like ladybugs and lacewings, which prey on aphids and other pests that can plague our crops.

Good companions include tomatoes and peppers, as Yarrow helps repel common pests that target these plants. It also works well with herbs like rosemary and thyme, enhancing their growth and flavor. Strawberries also benefit from Yarrow's presence, as it attracts pollinators and deters pests. Avoid planting Yarrow near plants in the Brassica family (cabbage, broccoli, kale), as it can attract cabbage moths.