Mowing Won’t Fix This One
Self-heal grows so low it flowers beneath your mower blades. It spreads by underground runners, forming dense mats that choke out grass. A selective lawn treatment kills the weed while feeding your grass to fill the gaps.
Self-heal is one of those lawn weeds in UK gardens that seems impossible to shift. You mow it, and it keeps flowering. You pull it up, and it grows back from fragments you missed. Its low-growing habit and aggressive spreading make it a persistent problem in lawns across the UK.
The good news is that self-heal responds well to selective weedkillers, and with the right approach you can eliminate it without harming your grass. Understanding how it grows and spreads is the key to getting rid of it for good.
How to Identify Self-Heal
Self-heal (Prunella vulgaris) goes by several names including heal-all, carpenter’s weed and wild sage. It’s a perennial weed, meaning it survives winter and returns year after year if left untreated.
The leaves grow in opposite pairs along square stems, a characteristic it shares with other members of the mint family. They’re oval-shaped with pointed tips, around 2cm long, and may be smooth or slightly hairy depending on the plant’s age.
The most distinctive feature is the flowers. Between June and September, self-heal produces dense spikes of purple to violet tubular flowers that sit just above the foliage. These flowers are attractive to bees and butterflies, but that doesn’t make them any less of a problem in your lawn.
Self-heal grows extremely low to the ground, which is why mowing has almost no effect on it. The plant can flower on stems just 3cm tall, well below the cutting height of most mowers.
Why Self-Heal Is Hard to Control
Self-heal spreads in two ways, and this dual attack is what makes it so difficult to eradicate.
First, it produces seeds from those purple flowers. Each plant can generate hundreds of seeds that remain viable in the soil, ready to germinate when conditions suit.
Second, it spreads vegetatively through stolons, which are creeping stems that run along the soil surface and root at intervals. These runners allow self-heal to colonise new areas quickly, forming dense mats that smother the grass beneath.
Because it roots at multiple points along those runners, pulling up one plant often leaves fragments behind that simply regrow. The shallow but extensive root system makes complete removal by hand extremely difficult.
Self-heal thrives in conditions where grass struggles. Compacted soil, nutrient deficiency, excessive thatch and close mowing all create opportunities for this weed to establish. You’ll often find it growing alongside other weeds like dandelions and clover in neglected or poorly maintained lawns.
Hand Removal
For small infestations of just a few plants, hand removal is worth trying before reaching for weedkiller. The best time is after rain when the soil is soft and roots come out more easily.
Use a hand fork or daisy grubber rather than just pulling, as you need to get as much of the root system as possible. Rake the area first to lift the runners and make them easier to see, then work methodically to remove all the plant material.
Be prepared for regrowth. Self-heal is stubborn, and you’ll likely need to repeat the process several times over the growing season to catch any fragments that regenerate. Check the area every few weeks and remove any new growth before it has a chance to spread.
Hand removal works best as a maintenance approach for lawns that are already largely weed-free, catching the occasional self-heal plant before it establishes. For larger infestations, it’s simply too labour-intensive to be practical.
Using Selective Weedkiller
For established self-heal or larger patches, a selective lawn weedkiller is the most effective solution. These products kill broadleaf weeds like self-heal while leaving grass unharmed.
Look for products containing 2,4-D, dicamba or similar selective herbicides designed for lawn use. A combined feed and weed treatment works particularly well because it kills the self-heal while simultaneously feeding your grass to fill in the gaps left behind.
Apply when the weed is actively growing, typically between April and September. Choose a calm day with no rain forecast for at least six hours, and avoid treating during drought or frost. The soil should be moist and both grass and weeds growing strongly for best results.
Self-heal usually responds well to a single application, but check again after three to four weeks and retreat any survivors. The weed should show signs of yellowing and distortion within a week or two of treatment.
Preventing Self-Heal From Returning
Killing existing self-heal is only half the battle. Without addressing the conditions that allowed it to establish, you’ll be fighting the same weeds again next year.
Feed your lawn regularly with a quality lawn fertiliser in spring and autumn. Healthy, well-nourished grass grows thick and dense, leaving fewer gaps for weeds to colonise. Self-heal specifically thrives in nutrient-poor soil, so improving fertility makes a real difference.
Aerate compacted areas by pushing a garden fork into the soil or using a hollow-tine aerator. Compaction restricts root growth and weakens grass, giving weeds the upper hand.
Scarify in autumn to remove excessive thatch, that layer of dead organic matter that builds up on the soil surface. Too much thatch prevents water and nutrients reaching grass roots, creating exactly the stressed conditions self-heal loves.
Raise your mowing height slightly. Cutting too short stresses the grass and exposes soil to weed seeds. A height of 3-4cm keeps grass healthy while shading out germinating weeds.
Mow regularly during the growing season, and collect the clippings when self-heal is flowering to prevent seeds spreading. If you can remove the flower heads before they set seed, you’ll reduce the weed’s ability to spread.
Frequently Asked Questions
Is self-heal harmful to my lawn?
Yes. Self-heal forms dense mats that smother grass, competing for light, water and nutrients. Left unchecked, it will gradually take over affected areas and thin out your lawn.
Can I just keep mowing self-heal to control it?
No. Self-heal grows so low that it flowers below normal mowing height. Mowing alone won’t prevent it flowering, setting seed or spreading by runners.
How long does it take for weedkiller to kill self-heal?
You should see yellowing and distortion within one to two weeks. Complete death takes three to four weeks. Check for survivors and retreat if necessary.
Will self-heal come back after treatment?
Seeds can remain dormant in the soil, so some regrowth is possible. Improve lawn health through feeding, aerating and proper mowing to prevent reestablishment.
Is self-heal the same as dead-nettle?
No. They’re different plants, though both have square stems and belong to the mint family. Dead-nettle has heart-shaped leaves and different flower structure.
Stop letting self-heal take over your lawn. A selective lawn treatment kills the weed and feeds your grass in one application. For severe infestations where you want to start fresh, glyphosate kills everything before reseeding. For more lawn weed advice, see our guides to plantain, speedwell and yarrow.
