- Use a garden fork or tiller to loosen the soil in your garden to about 12 to 15 inches deep, then mix in a 2– to 4–inch layer of compost.
- Plant in the spring in well-drained, average to poor soil. Yarrows thrive in hot, dry conditions; they will not tolerate wet soil. If you grow yarrows in rich soil, the plants may require stalking because the rich soil encourages growth.
- Space the plants 1 to 2 feet apart. They are quick to establish and spread, though some species, like Achillea millefolium, are invasive, so be careful when choosing your plants. Most kinds grow to be about 2 to 4 feet tall.
- Remember to add a thin layer of compost, followed by a 2–inch layer of mulch around your plants each spring.
- If you receive less than 1 inch of rain a week in the summer, remember to water your plants regularly.
- Divide yarrow plants every 3 to 5 years. Lift the clumps of flowers in early spring or fall and remove any dead stems from the center of the clump. You can replant the divisions in well-prepared soil.
- If you plant yarrows from tip cuttings, plant them in spring or early summer.