Achillea millefolium var. occidentalis. This is an important native North American wildflower and pollinator plant. It thrives particularly in recently disturbed soil. Because of this feature, Western Yarrow seeds are especially useful for planting around work sites, septic berms, or roadside areas. This variety grows 25-90cm (10-36" tall, with densely hairy, lacy, fern-like leaves. It has an extended bloom period from May to September, and is very attractive to beneficial insects, including predatory wasps, ladybird beetles, and hover-flies. Western Yarrow is also highly drought-resistant, so it's excellent for xeriscaping and erosion control. It is widely used in New Zealand as pasture.
The scent of yarrow repels aphids, but attracts hoverflies, lady beetles, and wasps that prey on garden grubs. The leaves and stems of yarrow contain enzymes that break down rapidly, so it can be added to the compost raw or as a tea to accelerate the heap. Achillea is a hardy perennial also known as milfoil. Follow along with this handy How to Grow Achillea Guide.
Season & Zone
Exposure: Full sun
Sow indoors 8-10 weeks before planting out, so around mid-March on the coast. Transplant or direct sow in early spring or early autumn. Optimal soil temperature for germination: 15-18°C (60-65°F). Seeds can take 10 to as long as 100 days to sprout. Bottom heat speeds germination.
Sow on the surface of the soil, under bright lights if starting indoors. Transplants can go out while the soil is still cool and there is still some risk of light frost. Space transplants at 30-60cm (12-24″) apart.
Yarrow is a tough plant that is suitable for xeriscaping, and it will adapt to pretty much any soil. For best results, grow in a loamy, well drained soil with a pH of 5.5 to 7.0. Divide plants every 3-4 years. Cut plants to ground level in autumn.