Weed, Feed and Moss Killer: Which to Use and When
Use a combined weed, feed and moss killer when your lawn has weeds, moss and hunger at the same time, typically in spring and early autumn. Use a straight lawn feed when the grass is just hungry, and an iron treatment when moss and poor colour are the main problem. Timing and the right product matter more than dose.
Weed and feed, moss killer, lawn feed: they sound similar and the labels do not always help. The simplest way to choose is to match the product to what your lawn actually needs right now, and to the time of year. Here is how the main lawn treatments differ and when to reach for each.
What is the difference between weed and feed and moss killer?
There are four common types of lawn treatment. A plain lawn feed (fertiliser) feeds the grass only, with no weed or moss control. A weed and feed feeds the grass and adds a selective weedkiller that targets broadleaf weeds such as dandelions, clover and daisies while leaving the grass unharmed. A moss killer is usually iron based: it blackens and kills moss and greens the grass, but does nothing to weeds. A 3-in-1 feed, weed and moss killer does all three in a single pass, which is handy when your lawn needs feeding and has both weeds and moss.
When should you use weed and feed in the UK?
Apply weed and feed when the weeds are actively growing and the grass is growing too, which is roughly April to September. Pick a dry day with light rain expected within a day or two to wash the feed in, but avoid heavy rain that would wash the weedkiller straight off. Do not apply to a drought-stressed lawn or in very hot weather, and never use weed and feed on a newly seeded lawn until it has been mown a few times.
How do I get rid of moss and green up the lawn?
Moss thrives in shade, compaction, poor drainage and acidic, hungry soil. An iron-based treatment kills moss quickly and gives a fast green-up, but that treats the symptom. To keep moss away for good, also fix the cause: scarify out the dead moss, aerate compacted areas, and feed regularly so the grass can out-compete it.
Can you feed and treat weeds at the same time?
Yes, and that is exactly what a combined product is for. It saves you a job when weeds, moss and hunger all show up together, which is common in spring and early autumn. But if you only have one problem, a targeted product is better value and gentler on the lawn. Feed alone when the grass is simply hungry, reach for the iron treatment when moss and colour are the issue, and use the 3-in-1 only when all three need tackling at once.
MyLawn is our free lawn-care app. Tell it about your lawn and it gives you a clear red, amber or green steer on what to do next, in plain English, paced to the season. Learn more about MyLawn.
Related Mowd guides: Control weeds in your lawn · browse the full lawn fertiliser range.
Frequently asked questions
When should I apply weed and feed in the UK?
- Apply from April to September when both the weeds and the grass are actively growing. Choose a dry day with light rain due within a day or two to wash in the feed, and avoid hot, dry spells.
Can I use weed and feed and moss killer together?
- A 3-in-1 product combines all three, so you do not need to mix them. If you only have one issue, a single-purpose treatment is more economical and kinder to the lawn.
How long after weed and feed can I mow?
- Leave it three to four days before mowing, and ideally do not collect the first cut or two so the weedkiller has time to work. Always follow the times on the pack.
Will moss killer harm my grass?
- Iron-based moss killers are designed to blacken and kill moss while greening the grass. The lawn may darken briefly where the moss dies back; rake it out after a couple of weeks. Follow the label rate to avoid staining paving.