Growing Yarrow 'Terracotta' in a pot

Once established, Achillea 'Terracotta' is one of the easiest perennials you can grow, with low water and nutrient needs. Water new plants regularly through their first summer, but after that irrigation is rarely necessary except during prolonged drought. Yarrow's deep taproot seeks out moisture, and overwatering or poorly drained soil causes root rot and encourages mildew. In a typical British summer, rainfall is usually sufficient. Feed sparingly. Too much fertiliser, especially nitrogen, produces lush foliage at the expense of flowers and makes stems flop. A single application of a balanced general-purpose granular fertiliser in April or May is plenty—scatter a light handful around the base of each clump and water in if the soil is dry. On fertile soils you can skip feeding altogether. Avoid high-nitrogen lawn feeds or fresh manure. Achillea is fully hardy to zone 3, so overwintering in temperate Europe presents no difficulty. Leave the old stems standing through winter if you wish, or cut back in March as described. No protective mulch or covering is needed. The main enemy is winter wet rather than cold, so ensure drainage remains good. Powdery mildew can appear as a white coating on leaves during humid weather or if plants are crowded or stressed. Improve air circulation by thinning congested clumps and avoid overhead watering. Aphids occasionally cluster on young shoots in spring; a strong jet of water usually dislodges them, or tolerate low numbers as they attract beneficial insects. Slugs and snails generally leave the aromatic foliage alone. Overall, 'Terracotta' is a robust, trouble-free plant that rewards neglect better than fussing.