Botanical name – Achellia millefolium
Family – Asteraceae
Aliases – common yarrow, milfoil, devil’s nettle, carpenter’s weed, bloodwort, nosebleed, old man’ pepper, staunchgrass
Yarrow is a perennial broad-leaf weed that is very common in all types of turf, as well as meadows, roadside verges, hedgerows and other grassy places. It thrives in most conditions, but is particularity happy in nutrient deficient, dry soils.
It is very tolerant of drought conditions and during extremely hot, dry summers, when the turf has turned brown, yarrow often remains a healthy green colour.
Yarrow can grow up to 80 cm tall if it is left undisturbed, however in closely mown turf it adapts to the height of cut and forms as a low growing mat. This weed spreads by underground runners (rhizomes), rooting at intervals. Yarrow roots can penetrate up to 20 cm deep. It will also reproduce via seed.
This plant has a number of medicinal uses, including healing infections, cuts and wounds to name a few. The leaves are also edible and can be used in salad mixes. The leaves have also been used to flavour beer and when mixed with the flowers they make an aromatic herbal tea.
The lanceolate leaves of yarrow have a very fine, feathery and fern like appearance to them, as they are finely cut into linear segments. When crushed the leaves give off a sweet fragrant smell reminiscent of Chrysanthemums . The lower leaves at the base of the rosette typically measure between 10 – 20 cm long.
The flowering period is between June and September as it produces flat, dense clusters of small white or pale yellow flowers. Quite often the flowers do not form if the grass is frequently mown.
Yarrow has a deep and fibrous root system consisting of numerous underground runners. These runners help the weed establish in turf and making it difficult to control and enable it to withstand drought conditions.
Yarrow Images (click image to enlarge)
Prevention and control
Encourage healthy turf with a balanced feed program. A vigorous, thick sward helps prevent weeds from encroaching.
Mow frequently to help prevent the flowers and seed heads from forming.
Irrigate during times of drought to prevent stress to the turf and retain good grass coverage.
Yarrow can be hand weeded taking care to remove the roots.
Yarrow is a difficult weed to control with a selective herbicide, as it is difficult to wet the foliage of the fine waxy leaves with weed. In almost all cases more than one treatment will be needed to control this weed. Even then the weed may still persist and further treatments the following season may be needed.
Recommended products for yarrow control
Professional products (The user requires the appropriate certificate/s to apply these products). These products will prove more effective against yarrow than those available for non-professional use.
Headland Cabadex (Fluroxypyr, Flurosulam)
React Ultra (Mecoprop-p, Dicamba, MCPA)
Everris Praxys (Clopyralid, Fluroxypyr, Fluosulam)
Products available for non-professional use (These products are available from garden centres and DIY stores)
Resolva lawn weed killer (2,4-D, Mecoprop-p, MCPA, Dicamba)