What is yarrow?
Yarrow is a rhizomatous, mat-forming and often invasive perennial plant with aromatic ferny grey-green foliage. It produces white or pinky-white daisy-like flattened flowerheads from early summer to late autumn.
Able to grow in any soil, yarrow survives dry, infertile conditions and close mowing. It will vigorously regrow from creeping underground stems and seed, outcompeting lawn grass to produce large drought-resistant patches.
Why is yarrow a problem?
Yarrow is often abundant on gravelly or chalky soils where plant nutrients are deficient, as it is very drought resistant. When grass is weakened by long periods of drought and lack of plant nutrients, yarrow thrives and can quickly establish in a lawn.
Control
Yarrow is a difficult weed to control once it is established in lawn grasses or turf so good lawn care is an effective preventative measure.
Non chemical control
A number of practical approaches can be taken;
- Encourage vigorous grass growth by applying a proprietary top-dressing in early spring at 1-4kg per sq m (2-7.5lb per sq yd) working in well with a rake or broom
- Over-application may impede mowing so a trial application is advisable
- Apply a further dressing in September at a heavier rate
- Feed the grass when it is growing actively with proprietary spring and summer lawn fertilisers, taking care to follow manufacturers instructions
- During the growing season the grass should be cut regularly and lightly raked, then after two or three days, cut again, removing the long growth
- Repetition of this treatment weakens the weed and strengthens the grass
- Regular watering at seven or eight day intervals during dry periods is essential to maintain vigour in the turf
Note: Avoid feeding a lawn when it is drought-stressed.
Chemical control
Use of chemicals may eventually eliminate the weed. However, feeding and regular top-dressing will encourage better grass growth, and make conditions less favourable for the weed seedlings to re-establish.
Yarrow is fairly resistant to many selective weedkillers used for weed control in turf but it may be worth trying;
- Repeated applications of weedkillers containing 2,4D, plus mecoprop-P or dicamba (e.g. SBM Job Done Lawn Weedkiller, Garden Direct Lawn Weed, Feed & Mosskiller (also contains fertiliser and mosskiller) or Scotts Lawn Builder Lawn Food Plus Weed Control (also contains fertiliser)) can be affective
Treated clippings
Do not add the first lawn clippings after application of a lawn weedkiller to the compost heap. To avoid possible contamination of compost, do not collect the clippings at all but mow frequently and allow the short clippings to remain on the surface of the lawn. These will quickly disperse to leave an acceptable finish.
New lawns
Weedkillers often cause severe damage if applied to lawns within six months of sowing or turf-laying.
Inclusion of a weedkiller product does not indicate a recommendation or endorsement by the RHS. It is a list of products currently available to the home gardener.
Download
Weedkillers for gardeners (Adobe Acrobat pdf document outlining weedkillers available to gardeners; see sections 1b, c and d)
Links
Chemicals: using a sprayer
Chemicals: using safely and effectivelyChemicals: using spot and broad-scale weedkillers Weeds: non-chemical control
Problems
Contact with yarrow foliage may aggravate skin allergies.
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