Yarrow is an invasive perennial weed with feathery, fern like leaves. It also known as common yarrow, nosebleed plant, devils nettle, thousand leaf and milfoil. This weed can quickly colonise a lawn as it spreads via underground runners known as ‘rhizomes’. Yarrow can tolerate close mowing as it adapts to the mowing height. Once it gets a foot hold it can spread quickly and be a major nuisance, as it is not easy to control yarrow.
The distinct leaves have a fern like appearance (see pictures) and give off a strong, fragrant smell when they are rubbed or crushed. The feathery leaves can grow between 25mm and 150mm in length depending on the conditions.
Yarrow flowers are bourne in umbrella shaped clusters, flowering from June to October. They may attract bees, as they provide a valuable source of nectar for them.
The weed will grow on most types of soil, however it is happiest on dry, chalky soils, especially those that are lacking in nutrition. Yarrow can easily tolerate drought conditions in the dry summer months.
Be vigilant and once yarrow has been identified, take immediate action by hand weeding, takeing care to remove the whole plant.
Regulary raking the weed prior to mowing will help weaken and remove the weed from the lawn.
Ensure good lawn health is maintained. The lawn should be fed with a suitable fertiliser to help maintain good grass coverage.
During periods of drought, periodically water the lawn to maintain good grass coverage. Avoid letting the grass stress out too much, when it is exceptionally dry.
Avoid mowing the lawn too short, especially during periods of drought.
Yarrow is resistant to most chemicals and success in removing it with a selective weed killer may be limited. A further application, about 6 weeks later will be needed. In an ideal world, deal with yarrow before it has chance to invade the lawn.