Achillea ageratifolia

The Achillea ageratifolia, also known as Ageratum-leaved yarrow, is a small yarrow plant that resembles Achillea umbellata. This small perennial plant forms dense, silvery cushions that are as pleasing to the eye as they are to the touch. Its aromatic and slightly fuzzy foliage remains evergreen throughout the winter. Its white flowers with pale yellow centres create a very bright combination with the cushion of leaves in late spring. This excellent rock garden perennial requires little maintenance. It can be grown in full sun, in any well-drained soil, alone or in combination with other ground cover plants.

The Achillea ageratifolia, from the Asteraceae family, is native to the Balkans. The Royal Horticultural Society has awarded this perennial for its ornamental qualities and performance in the garden. The plant forms a cushion 15 cm (6in) tall when flowering 5 to 10 cm (2 to 4in) for the foliage, depending on the growing conditions. It spreads slowly on the ground for up to 30 cm through short stolons. Its foliage remains evergreen throughout winter in mild climates. Linear in shape, it is finely toothed and covered with a fine greyish-silver fuzz that becomes lighter in July-August, giving it a velvety appearance that is pleasant to the touch. When crushed, it releases a pleasant fragrance on the skin. Flowering occurs from May-June to July-August, depending on the climate. The flower heads are pure white with a creamy yellow centre.

All yarrows thrive in the sun and are extremely hardy. The Achillea ageratifolia, requiring very little maintenance, is a small ground cover that can be used in a rock garden, of course, along the edge of a flower bed if the soil is well-drained. It is an excellent solution for dry slopes as it is water-efficient and non-invasive. It also helps to prevent the spread of unwanted plants, giving the garden a pristine, silver appearance. It can be paired with other low-growing or cushion-forming plants such as Geranium sanguineum, Erigeron karvinskianus, Nepeta x faassenii, etc. Many combinations are possible, including dwarf Teucrium, Aphyllantes monspeliensis, Artemisia lanata, Centaurea bella, Thymus (hirsutus, ciliatus, lanigerus), or other yarrows (millefolium, coarctata, nobilis).