The RHS believes that avoiding pests, diseases and weeds by good practice in cultivation methods, cultivar selection, garden hygiene and encouraging or introducing natural enemies, should be the first line of control. If chemical controls are used, they should be used only in a minimal and highly targeted manner.
Try cultural methods first;
- Apply a spring lawn fertiliser, high in nitrogen, in March. This will boost desirable lawn grasses as they come into growth
- Mow regularly, as fine grasses are better adapted to being cut, while coarse grasses are weakened by this treatment
- Rake the lawn lightly with a spring-tine rake to lift up the patches of coarse grass before mowing. This will allow a better cut and aid coarse grass removal. Take care not to mow too low
- Remove individual patches of weed grasses by hand
- For large problem areas, fork out the worst patches in September or October (adding soil to re-establish the level) and then re-seed with a fine lawn seed mixture, or lay patches of new turf
Poa annua (annual meadow grass):
- For specific problem areas, fork out the worst patches in September or October (adding soil to re-establish the level) and then re-seed with a fine lawn seed mixture, or lay patches of new turf
- If infestation is extensive, control is much more difficult. Avoid frequent watering in dry summers, as meadow grass is shallow-rooting, so should be discouraged by drought
- Poa annua will not survive if the soil is very acid, so avoid applying lime to the turf or using lime-based fertilisers such as nitro-chalk. Use sulphate of ammonia, which is acidic, to feed the turf, but only in moderation – if conditions become too acid this might adversely affect other desirable grasses
Coarse creeping grasses:
- Rake the lawn regularly before mowing in summer and autumn, using a spring-tine rake. This lifts up the stems so they are more easily cut by the mower. Do not rake vigorously in spring, as this is the time of year when new shoots of fine grasses are rooting into the soil. Disturbance of this rooting process could result in sparse turf that is more open to weed infestation
- Apply a proprietary lawn dressing (or a mixture of equal parts good loam soil, sieved leafmould and sharp sand) in September
- Feed the lawn annually in spring to encourage the growth of desirable turf grasses
There are no selective weedkillers that can be used against coarse grasses in lawns without also killing the turf grasses.