Yarrow in May: monthly care

Achillea millefolium thrives in full sun but tolerates partial shade, though flowering may be less prolific in shadier spots. It's exceptionally adaptable to soil type, growing happily in sandy soil, loam, or chalky soil, and it actually prefers lean, free-draining conditions over rich, heavy ground. Avoid waterlogged sites; yarrow dislikes wet feet and may rot in poorly drained soil. You can plant yarrow from March to May or in September and October. Spring planting gives plants a full season to establish, while autumn planting works well in milder areas, allowing roots to settle before winter. Prepare the soil by removing weeds and forking it over lightly—there's no need to add compost or manure, as yarrow performs better in less fertile ground. If your soil is heavy clay, work in some grit or sharp sand to improve drainage. Plant at the same depth the plant was growing in its pot, spacing individual plants 40 cm apart to allow for their spreading habit. Yarrow forms clumps that gradually expand via rhizomes, so give them room. After planting, firm the soil gently around the roots and water in well to settle them, even though yarrow has low water needs once established. Apply a light mulch of gravel or grit around the base if your soil is on the heavy side; this keeps the crown dry and discourages rot. Avoid organic mulches like bark or compost, which can make the soil too rich and cause floppy growth. Water occasionally during the first few weeks if the weather is dry, but yarrow establishes quickly and soon becomes drought-tolerant.

Yarrow is a low-maintenance perennial that tolerates neglect once established. Its water needs are low; in fact, overwatering or rich, moist soil often causes weak, floppy stems. Water new plants during dry spells in their first season, but after that, rainfall is usually sufficient. In prolonged summer drought, an occasional deep soak is appreciated, but yarrow copes admirably without it. Feeding should be minimal. In April or May, scatter a light dressing of general-purpose granular fertiliser (such as blood, fish and bone) around the base of the plant, or skip feeding altogether if your soil is reasonably fertile. Too much nitrogen results in lush foliage that flops and is prone to mildew. Yarrow evolved on poor soils and doesn't need pampering. Overwintering is straightforward. Yarrow is fully hardy down to zone 3, so it sails through British and Irish winters without protection. Cut back dead stems in late autumn or early spring, and the plant will reshoot reliably from the base. No mulching or covering is necessary. Pests rarely trouble yarrow—it's actually known for attracting beneficial insects like hoverflies and ladybirds. The main issue to watch for is powdery mildew, which can appear as a white, dusty coating on leaves in humid or crowded conditions, especially in late summer. Improve air circulation by thinning congested clumps every three to four years: lift and divide plants in spring or autumn, replanting only the vigorous outer sections. Good spacing and avoiding overhead watering also help prevent mildew. Otherwise, yarrow looks after itself with minimal fuss.