The Weed That Laughs at Drought
Yarrow stays stubbornly green while your grass turns brown in dry spells, making it impossible to ignore. Its waxy leaves resist most weedkillers, but a healthy, well-fed lawn can outcompete it naturally.
Yarrow is one of the most frustrating lawn weeds in the UK to deal with. Its feathery foliage looks nothing like grass, so it stands out even in a well-maintained lawn. During drought, when your grass goes brown and dormant, yarrow stays conspicuously green, drawing attention to every patch you’d rather not see.
What makes yarrow particularly challenging is its resistance to many selective weedkillers. The waxy coating on its finely divided leaves makes it difficult for herbicides to penetrate, often requiring multiple treatments where other weeds would die after one. Understanding how yarrow grows and spreads is essential if you want to get rid of it.
How to Identify Yarrow
Yarrow (Achillea millefolium) is unmistakable once you know what to look for. The leaves are its defining feature: soft, feathery and fern-like, with a grey-green colour that contrasts with the brighter green of lawn grass. Each leaf is finely divided into countless tiny segments, which is why it’s also called thousand-leaf or milfoil.
The leaves grow from a central rosette and can reach 10-20cm long when undisturbed, though in mowed lawns they stay much shorter. When crushed, they release a distinctive aromatic scent reminiscent of chrysanthemums.
If you let yarrow flower, it produces tall stems topped with flat, umbrella-shaped clusters of small white or cream flowers between June and October. In regularly mowed lawns you rarely see these, but the foliage alone is distinctive enough to identify.
Yarrow is a perennial weed, meaning it survives year after year. It spreads through underground rhizomes that root at intervals, allowing it to colonise large areas and form dense mats that smother the grass beneath.
Why Yarrow Thrives in Struggling Lawns
Yarrow is remarkably tough. It tolerates poor soil, drought and close mowing better than most lawn grasses, which is why it tends to appear in lawns that are already under stress.
The roots can penetrate up to 20cm deep, accessing moisture that shallow-rooted grass can’t reach. During hot, dry summers when your lawn turns brown, yarrow patches remain defiantly green. This drought tolerance is impressive, but it makes the weed extremely visible at exactly the time you’d rather it wasn’t.
Yarrow particularly thrives in nutrient-poor, dry and compacted soils. If you see it appearing in your lawn, it’s often a sign that the soil needs attention. You might also find it growing alongside other weeds that favour similar conditions, like self-heal and clover.
Why Yarrow Resists Weedkiller
The fine, waxy leaves that make yarrow so drought-tolerant also make it resistant to herbicides. Spray lands on the surface but struggles to penetrate and be absorbed by the plant.
This doesn’t mean weedkiller won’t work, but you’ll typically need multiple applications over the growing season rather than the single treatment that kills most lawn weeds. Products containing 2,4-D, MCPA, dicamba or mecoprop-P can control yarrow, but patience is required.
For best results, apply selective lawn weedkiller when yarrow is actively growing, typically between April and September. Choose calm, dry conditions with no rain forecast for at least six hours. Repeat the treatment after four to six weeks if the yarrow persists.
Some professional products containing fluroxypyr or clopyralid are more effective against yarrow, but these aren’t available to home gardeners. If repeated DIY treatments fail, it may be worth calling in a lawn care professional with access to stronger products.
Digging Out Yarrow
Hand removal is possible but demanding. Yarrow’s rhizome system means you need to remove every fragment of root, as any piece left behind will regrow into a new plant.
Use a garden fork rather than a trowel, working down at least 15-20cm to get beneath the root system. Lift out the entire plant including all visible rhizomes, then sift through the soil to remove any broken pieces.
This approach works for isolated plants, but it’s impractical for large infestations. You’ll also leave bare patches that need reseeding, and there’s no guarantee you’ve removed every root fragment. Expect to repeat the process as regrowth appears.
Where yarrow has formed extensive mats, you may need to remove entire sections of lawn and start again with fresh turf or seed. For total clearance before reseeding, glyphosate kills everything including the grass. This is drastic but sometimes the only way to achieve complete removal.
Preventing Yarrow From Returning
The most effective long-term strategy is to create conditions where grass thrives and yarrow struggles. This means addressing the underlying problems that allowed yarrow to establish in the first place.
Feed your lawn regularly with a quality fertiliser in spring and autumn. Yarrow thrives in nutrient-poor soil, so improving fertility gives grass the upper hand. A combined feed and weed treatment tackles existing weeds while strengthening your grass.
Water your lawn during prolonged dry spells. While established lawns can survive drought by going dormant, the brown grass creates perfect conditions for drought-tolerant yarrow to spread. One thorough watering per week during dry periods keeps grass growing strongly enough to compete.
Aerate compacted areas annually to improve drainage and root development. Scarify in autumn to remove thatch, which can prevent water and nutrients reaching grass roots.
Mow regularly at a height of 3-4cm. Cutting too short weakens grass and exposes soil to weed colonisation. Collect clippings when yarrow is flowering to prevent seeds spreading.
Frequently Asked Questions
Why does yarrow stay green when my grass goes brown?
Yarrow has deep roots (up to 20cm) and waxy leaves that retain moisture. It can access water that shallow-rooted grass can’t reach, so it survives drought conditions that stress lawns.
Is yarrow resistant to weedkiller?
Partially. Its waxy leaves make herbicide absorption difficult. You’ll typically need multiple applications of selective weedkiller over the growing season rather than a single treatment.
Can I dig out yarrow by hand?
Yes, but it’s difficult. You must remove all root fragments, as any piece left behind will regrow. Dig at least 15-20cm deep and expect to repeat as regrowth appears.
Is yarrow bad for my lawn?
It forms dense mats that smother grass, competing for light, water and nutrients. The feathery foliage also looks distinctly different from grass, spoiling the appearance of a uniform lawn.
Does yarrow have any benefits?
Yes. It’s excellent for pollinators and supports over 100 insect species. If you have a wildflower meadow or informal garden, yarrow is valuable. But in a formal lawn, it’s a weed.
Yarrow takes persistence to control, but a healthy lawn is your best defence. Regular feeding, proper watering and good maintenance create conditions where grass outcompetes this stubborn weed. For existing infestations, a selective lawn treatment applied repeatedly will gradually weaken it. See our guides to dandelions, plantain and sheep’s sorrel for more lawn weed advice.
