Achillea odorata

Achillea odorata is also called fragrant yarrow due to the strong absinthe aroma that its foliage contains. This vigorous perennial plant from limestone scrubland is capable of forming a wide and dense evergreen and highly decorative feathery carpet. Its foliage is finer and greener than that of its cousin Achillea crithmifolia. In early summer, it is adorned with small dirty white to yellowish umbels. Perfectly hardy and tolerant to summer drought, it can withstand moderate trampling, making it suitable as an alternative to lawns. It can be grown in full sun or partial shade,  in any well-drained soil, alone or in association with other ground cover plants.

Achillea odorata, from the Asteraceae family, is native to southern Europe, Tyrol in Austria, and the Istria region in Croatia. It grows on hillsides and along paths in mostly limestone soil. The plant forms a vigorous natural-looking ground cover, 30 to 50cm (12 to 20in) tall when flowering, sometimes more in moist and fertile soil. It spreads relatively quickly, up to 50cm (20in), through stolons. Its evergreen foliage remains green throughout summer, even in intense drought. Finely dissected, feathery, greyish-green, and slightly hairy, it has a fluffy appearance but a somewhat rough texture. When crushed, the foliage releases a strong smell reminiscent of absinthe. Flowering occurs in June-July, sometimes as early as May in warm climates. The inflorescences are small, slightly globular umbels, 3 to 4cm (1 to 2in) in diameter, composed of tiny flowers with an uncertain white colour and creamy-yellow centre. This plant releases molecules through its roots that inhibit the germination of other plants through allelopathy, which ultimately reduces the need for weeding.

All yarrows thrive in full sun and are excellent in terms of hardiness. Achillea odorata requires very little maintenance and can go without watering in all regions, making it a great substitute for lawns in moderately trafficked areas of the garden. With no soil requirements and being water-efficient, it limits the proliferation of weeds and gives a natural look to the garden while eliminating the need for regular mowing (and watering) required for a lawn, even in dry climates. Only one mowing is required after flowering to encourage new foliage growth. It can be paired with other vigorous ground cover plants with complementary growth cycles, such as Phyla nodiflora: in the middle of summer, phyla dominates with its flowers, and in winter, achillea's green foliage takes over. This lovely combination can also effectively cover the ground in solid perennial beds, with plants such as Geranium sanguineum, Erigeron karvinskianus, and Nepeta x faassenii, etc. Many combinations are possible, including Thymus (hirsutus, ciliatus), other yarrows (millefolium, crithmifolia, coarctata, nobilis), Dichondra repens, and Matricaria tchihatchewii, etc.