It Looks Like Moss But It’s Not
Pearlwort forms moss-like mats in lawns and many gardeners reach for moss killer before realising their mistake. This perennial weed has waxy leaves that resist most herbicides, often needing multiple treatments to control.
Pearlwort (Sagina procumbens) is one of the most commonly misidentified lawn weeds. Its low, mat-forming habit and tiny narrow leaves give it a moss-like appearance that fools many gardeners. But while moss killers have no effect on it, pearlwort responds to selective herbicides, though often reluctantly. It’s one of the weeds found in UK gardens that requires persistent treatment.
This perennial weed is particularly troublesome on fine turf, bowling greens and closely mown lawns. It tolerates extremely close mowing and actually thrives where grass is cut short, spreading steadily to form dense patches that crowd out the grass beneath.
Why Pearlwort is Difficult to Control
Pearlwort has several characteristics that make it a persistent problem. The leaves have a thick, waxy cuticle that acts as a barrier to herbicide absorption. This waxy coating means chemicals don’t penetrate as effectively as they do on other broadleaf weeds, often requiring repeat applications.
The plant spreads by both seed and creeping stems. Stems root at the nodes as they spread outward, quickly forming an interconnected mat. Like mouse-ear chickweed, pulling one section leaves rooted fragments that regrow.
Pearlwort flowers from May to September, producing tiny blooms that are easy to miss. Each flower produces numerous seeds, constantly adding to the soil seed bank. The weed favours damp conditions and is especially common in frequently watered lawns and coastal areas where humidity is high.
The shallow, fibrous root system makes hand removal possible but tedious. You need to lift every rooted section, and the interweaving stems make this slow work. Miss any fragments and regrowth is rapid.
Identifying Pearlwort
The key to identifying pearlwort is looking closely at the foliage. The leaves are tiny, narrow and blade-like, typically 10-20mm long with pointed tips. They grow opposite each other on thin stems, creating a dense, tuft-like appearance.
Unlike moss, which has no true stems or leaves, pearlwort has a distinct plant structure when examined closely. The stems are clearly visible, spreading outward from a central rosette and rooting at intervals. The overall effect is more structured than the soft, cushiony growth of moss.
The flowers are minute, just 2-4mm across, with four white petals that are sometimes absent entirely. You need to look closely to spot them on thin stalks near the stem tips. The flowering period runs from May through September.
Pearlwort also grows readily in paving cracks and between slabs, where it resists trampling well. If you have moss-like growth in your patio cracks that doesn’t respond to moss treatment, it’s likely pearlwort.
Cultural Control Methods
Good lawn care reduces pearlwort’s opportunities. The weed establishes most readily in thin, weak turf with bare patches. A thick, healthy sward leaves less space for pearlwort to colonise.
Address drainage issues where possible. Pearlwort thrives in damp conditions, so improving soil drainage makes your lawn less hospitable. Hollow-tine aeration helps water drain through rather than pooling on the surface.
Avoid overwatering. If you irrigate your lawn, water deeply but infrequently rather than little and often. Constant surface moisture favours pearlwort establishment. In most UK summers, established lawns rarely need supplemental watering.
Raise your cutting height slightly. While pearlwort tolerates close mowing, taller grass competes more effectively and shades the soil surface. A height of 3-4cm gives grass an advantage without looking unkempt.
Hand removal works for small infestations caught early. Use a hand fork to lift patches, taking care to remove all rooted stems. Check the area regularly and remove any regrowth before it spreads.
Using Selective Weedkiller
For established pearlwort, selective herbicide treatment is usually necessary. The waxy leaf coating means you’ll likely need more than one application, unlike easier weeds such as daisies or dandelions that often succumb to a single treatment.
Selective lawn treatments containing 2,4-D, mecoprop-p, dicamba or fluroxypyr can control pearlwort. Apply when the weed is actively growing, typically between April and September. Choose a dry, still day when no rain is forecast for 24 hours.
Don’t mow for three days before treatment to maximise leaf area for absorption. Wait another three days after treatment before mowing. The more chemical the plant absorbs, the better your results.
Expect to need a follow-up application four to six weeks after the first treatment. The waxy leaves mean initial absorption is limited, so a second dose is usually required for complete control. Some stubborn patches may need a third treatment.
For widespread infestations, treat the whole lawn rather than spot spraying. This ensures you catch all the interconnected growth and any isolated patches you might miss. A dilutable concentrate applied with a sprayer is more economical for large areas.
For severe cases where grass is largely displaced, you may need to use glyphosate to clear the area completely and start fresh with new seed or turf.
Preventing Reinfestation
After successful treatment, overseed any bare patches promptly. Dead pearlwort leaves gaps that new weeds quickly colonise. A thick grass sward is your best long-term defence against reinfestation.
Maintain good lawn care practices. Regular feeding keeps grass vigorous and competitive. Annual aeration improves drainage. Appropriate mowing height gives grass an advantage over low-growing weeds.
Watch for new seedlings in spring and early summer. Young pearlwort plants are much easier to control than established mats. Remove them promptly or treat early before the waxy cuticle fully develops.
Frequently Asked Questions
Is pearlwort the same as moss?
No. Pearlwort is a flowering plant with true stems, leaves and roots. Moss is a non-flowering plant with a completely different structure. Moss killers don’t work on pearlwort, and selective weedkillers don’t affect moss. Identify correctly before treating.
Why doesn’t weedkiller work on pearlwort?
Pearlwort leaves have a thick waxy coating that reduces herbicide absorption. Unlike most broadleaf weeds that die after one treatment, pearlwort usually needs two or three applications. Persistence is key.
Can I dig pearlwort out of my lawn?
Yes, but it’s time-consuming. The creeping stems root at every node, so you need to lift the entire mat including all rooted sections. For small patches caught early, hand removal works. For larger infestations, herbicide is more practical.
When is the best time to treat pearlwort?
Apply selective weedkiller between April and September when the plant is actively growing. Avoid treating during drought, frost or before rain. Plan for repeat applications four to six weeks apart.
Will pearlwort spread to my whole lawn?
If left unchecked, yes. Pearlwort spreads by both seed and creeping stems, gradually expanding its territory. Early treatment prevents small patches becoming major infestations.
Pearlwort tests your patience with its herbicide-resistant waxy leaves, but control is achievable with persistence. Correct identification is the first step, so don’t waste time on moss killer if pearlwort is your problem. Selective weedkiller applied two or three times will bring it under control. For help identifying other problem weeds, see our guide to common lawn weeds and mind-your-own-business.
