The Clover Killer in Your Lawn Weed Killer
Mecoprop-P is the active ingredient that tackles the weeds other lawn herbicides miss — especially clover and speedwell. Here’s what it does and how it works.
What Is Mecoprop-P?
Mecoprop-P (often abbreviated to MCPP-P) is a selective herbicide that kills broadleaf weeds in lawns while leaving grass unharmed. It works in the same way as MCPA and 2,4-D — by mimicking plant growth hormones — but it’s effective against a different range of weeds.
Its real value is in combination products. Where MCPA excels at thistles and docks but struggles with clover, mecoprop-P picks up the slack. That’s why most off-the-shelf lawn weed killers contain two or three active ingredients working together.
What Does Mecoprop-P Kill?
Good control (mecoprop-P’s strength):
- Clover (white and red) — the weed it’s most valued for controlling
- Speedwell (slender and germander)
- Chickweed
- Pearlwort
- Trefoil (lesser and bird’s foot)
- Mouse-ear chickweed
In combination with MCPA/2,4-D, also controls:
- Thistles, docks, buttercups, daisies, plantain, dandelions
This is why the combination approach is so effective. On its own, mecoprop-P wouldn’t control thistles or docks reliably. Paired with MCPA, the mix covers almost every common lawn weed.
How Combination Products Work
The most common combinations in UK lawn products are:
Each active ingredient has its strengths and weaknesses. By combining them, manufacturers create products that control the widest possible range of lawn weeds in a single application. It’s the same principle behind the strongest weed killers — multiple modes of action working together.
How to Get the Best Results
The application advice for mecoprop-P products is essentially the same as for any selective lawn herbicide:
- Apply April to September when weeds are actively growing
- Don’t mow for 2-3 days before or after application
- Choose a dry, calm day — check our guide on weed killer and rain for timing
- Temperature above 10°C for best uptake
- Apply evenly — patchy application leads to patchy results
- Don’t over-apply — follow label rates. Excess product can scorch grass
For clover specifically, timing matters. Clover is most susceptible when it’s actively growing in spring and early summer. Treating in late autumn or winter is largely ineffective because the plants are dormant.
If clover is particularly dense, you may need two applications spaced 6-8 weeks apart. The first treatment weakens the plants, and the second finishes them off. See our timing expectations guide for realistic timelines.
Safety Considerations
Mecoprop-P shares the same safety profile as other phenoxy herbicides. Keep pets and children off the lawn for 24-48 hours after application. It’s harmful to aquatic life, so maintain a buffer zone from ponds and watercourses.
One specific note: mecoprop-P was historically a groundwater concern because the older formulation (racemic mecoprop) was more persistent. The modern “-P” version (the pure R-enantiomer) breaks down faster in soil and is far less likely to leach. This is why products have been reformulated — always buy products labelled “mecoprop-P” rather than old stock labelled just “mecoprop.”
Frequently Asked Questions
Is mecoprop-P the same as MCPA?
No. They’re related chemicals from the same family, but they control different weeds. MCPA is strongest against thistles and docks. Mecoprop-P is strongest against clover and speedwell. They’re often combined in the same product for broad-spectrum control.
Will mecoprop-P kill clover on its own?
It’s the best single active ingredient for clover control, yes. However, combination products (mecoprop-P + MCPA or 2,4-D) give more reliable results across a wider range of weeds. Dense, established clover may need two treatments.
How long does mecoprop-P take to work?
Expect visible wilting within 7-14 days. Complete kill takes 3-6 weeks. Clover can be slow to die back fully, so don’t assume it hasn’t worked if you still see green clover after two weeks — give it the full six weeks before considering retreatment.
Can mecoprop-P damage my lawn?
At recommended rates, no. All common lawn grasses tolerate mecoprop-P well. Over-application or applying to stressed, drought-damaged grass can cause temporary yellowing. Always follow the label dosage and don’t treat during drought or heat stress.
Is mecoprop-P safe for pets?
Keep pets off the lawn for 24-48 hours after treatment. Once the product has dried and been watered in, the risk is very low. See our full pet safety guide for more detail.
What if mecoprop-P doesn’t kill my clover?
Try a second application 6-8 weeks after the first. If clover persists, consider a product containing fluroxypyr, which is even more effective against established clover. Also check your lawn isn’t too thin — clover thrives in sparse grass, so overseeding and feeding can help prevent it returning.
Clover Taking Over Your Lawn?
A combination lawn weed killer with mecoprop-P is the most effective treatment for clover, speedwell and other stubborn lawn weeds.
