Yarrow in Zone 7A — Southeast

Yarrow is a fantastic addition to any Zone 7A garden. Its feathery foliage and clusters of blooms add beauty, and it attracts beneficial insects to keep your tomatoes and peppers happy. Plus, yarrow is incredibly easy to dry, so you can enjoy its beauty indoors long after our long summer growing season is over.

Our hot and humid summers can be tough on some plants, but yarrow thrives in these conditions, especially if you give it well-drained soil. With a growing season that stretches from late March to early November, you’ll have plenty of time to enjoy this hardy perennial.

Starting yarrow indoors isn't always necessary here in the Southeast, but it can give you a head start, especially if you want blooms the first year. If you choose to start indoors, do it from early to late January.

Use seed trays with a good seed-starting mix, and provide warmth and light – a heat mat and grow lights work well. Bottom watering can help prevent damping-off, a common problem with seedlings in our humid climate. Our moderate spring gives you plenty of time to get those seedlings ready for transplanting.

Transplant your yarrow seedlings outdoors from mid March through early April, once the danger of frost has passed. Before planting, harden them off for about a week by gradually exposing them to outdoor conditions.

Space them 12-18 inches apart in a sunny spot with well-drained soil. While we often have warm spells in early spring, keep an eye out for late frosts and be prepared to cover your young plants if needed. Buying starts from a local nursery is a great way to ensure you get blooms the first year.

Direct sowing yarrow is a simple and effective method, especially if you’re not in a rush for first-year blooms. Sow seeds from late March through mid August.

Prepare the soil by loosening it and removing any weeds. Yarrow prefers well-drained soil, so amend with compost or sand if you have heavy clay. Lightly press the seeds into the soil, keeping them 12-18 inches apart. Direct sowing is easy, but you'll need to be patient for blooms.

Yarrow is very drought-tolerant once established, which is a blessing during our hot and humid summers. The key is to avoid overwatering, which can lead to floppy growth and fungal issues.

In the spring, water regularly to help young plants establish. During our wet-summer months, you may not need to water at all unless we experience a dry spell. Use the finger test – if the top two inches of soil are dry, it's time to water. Aim for about an inch of water per week during dry periods. Water at the base of the plant to avoid wetting the foliage, which can encourage fungal diseases in our humid climate.

Signs of underwatering include wilting or yellowing leaves. Overwatering can cause yellowing leaves and root rot. A layer of mulch can help retain moisture and suppress weeds, but avoid piling it up against the stems, which can trap moisture and lead to rot.

Deadheading spent flowers will encourage a second flush of blooms and keep your yarrow looking tidy. Simply snip off the faded flower heads just below the bloom. Do this throughout the growing season, from late spring through late summer.

In the fall, after the first frost around early November, cut the plant back to its basal foliage. Yarrow can be aggressive, so divide the clumps every 2-3 years to keep it in check.

You can expect your first harvest of yarrow flowers about 65 days after planting, typically from late May through mid November. Harvest the flowers for drying when they are fully open and the colors are vibrant.

Cut the stems just above a leaf node, leaving plenty of foliage on the plant for continued production. Hang the stems upside down in a cool, dry, and dark place to dry. As the first frost approaches in early November, harvest any remaining flowers to dry indoors.

Yarrow is generally a low-maintenance plant, but here are a few common problems you might encounter in the Southeast:

Spreads aggressively:

• What it looks like: Yarrow can spread quickly via rhizomes, forming dense clumps that can crowd out other plants.
• What causes it: Our long growing season and reliable rainfall provide ideal conditions for yarrow to spread.
• 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 keep it in check. Remove unwanted seedlings promptly.

Powdery mildew:

• What it looks like: White or grayish powdery coating on leaves and stems. Leaves may curl, yellow, and die.
• What causes it: Powdery mildew thrives in warm days, cool nights, and moderate humidity, all of which we experience during certain times of the year in the Southeast.
• How to fix/prevent it: Improve air circulation by spacing plants adequately and pruning overcrowded foliage. Remove affected leaves promptly. Neem oil or potassium bicarbonate sprays can help. A milk spray (1 part milk to 9 parts water) is also effective.

Aphids:

• What it looks like: Clusters of tiny green, black, or white insects on stems and leaf undersides. Sticky honeydew residue. Curled or distorted new growth.
• What causes it: Aphids reproduce rapidly in warm weather, and our long, hot summers provide ample opportunity for populations to explode.
• How to fix/prevent it: Knock aphids off plants with a strong spray of water. Encourage natural predators like ladybugs and lacewings. Insecticidal soap or neem oil can be used for heavy infestations.

Southeast Specific Challenges: Our hot and humid summers create ideal conditions for fungal diseases like powdery mildew. Regular monitoring and good air circulation are key to preventing problems. While deer aren't as attracted to yarrow as they are to other plants, they may still nibble on it, so consider fencing if deer are a major issue in your area.

Yarrow makes a great companion plant in the Southeast garden. It attracts beneficial insects like ladybugs and lacewings, which prey on aphids and other pests that can plague our tomatoes and peppers.

Planting yarrow near herbs like rosemary and thyme can also deter pests. Strawberries benefit from yarrow's presence, as it attracts pollinators and beneficial insects that help control pests. Avoid planting yarrow near plants in the brassica family (cabbage, broccoli, kale), as it can attract cabbage moths.