Annual meadow grass
(Poa annua) Annual meadow grass is a common weed of lawns, beds, borders and containers. It sets a lot of seeds each year and so spreads readily around the garden.
What is annual meadow grass?
Annual meadow grass is, as its name suggests, an annual grass. It sets a lot of seeds each year and so spreads readily around the garden.
These seeds can remain dormant in the ground for several years. And as “One year’s seeding means seven years weeding”, allowing plants to flower and produce seeds, means several years of trying to control and remove it.
In the lawn, its annual growth habit means it produces bare areas, where moss and other weeds can then become established, when it dies out. It is one of the commonest coarse grasses that grows in the lawn. It can flower even when the lawn is regularly mown and the flowers and seed heads create a speckled effect.
Where does it grow?
- Gravel paths
- Between paving slabs
- Waste or uncultivated ground
Annual meadow grass has a slightly creeping habit and the stems can grow up to 25cm (10in) high, but much lower in closely mown lawns. The leaves are smooth with finely serrated edges.
It can flower all year around, except in severe winters. It grows rapidly from seed, starts flowering within six weeks, produces seeds and then dies.
How to control annual meadow grass
As with most weeds, never allow it to become established, and certainly don’t allow it to flower and produce seeds. This will make it more difficult, and more time consuming, to fully control. Early identification and eradication is important to stop it taking over the garden.
Regularly hoeing seedlings and young plants as soon as you see them is the quickest and easiest method of control. The aim of hoeing is to sever the weed stems at or just below ground level, cutting the top growth from its roots. A sharp hoe blade will make this even quicker and easier, so always sharpen the hoe blade before using it. Hoeing on a warm and/or windy day will mean they quickly dehydrate and die.
Digging out the plants when they are more established is more time consuming and more difficult – especially where they’re growing among wanted plants.
Flame guns and weeders that use an electric current are also effective in some locations.
Covering bare soil with weed-control membrane (landscape fabric) or even thick black polythene will exclude light and prevent seeds germinating. As will mulching the soil with organic matter, such as a bark mulch. For mulches to work properly, they need to be a minimum of 5cm (2in) thick, but 7.5cm (3in) deep works better.
Annual meadow grass is more difficult to control in lawns, and obviously lawn weedkillers have no effect. Regular feeding and mowing throughout the year should help prevent it becoming established in the first place.
Annual meadow grass does not like acidic soils, so avoid liming the soil – especially under the lawn. Lawn fertilisers are acidic in nature, so regular use should help acidify the soil.
There are a number of weed control options available to treat annual meadow grass. In addition to traditional weedkillers there are now also a range of more natural alternatives.
Any weedkiller can be used to control and kill annual meadow grass in beds, borders, waste ground and on paths. Those marketed as “fast acting” are contact weedkillers – killing or damaging the plant tissue they are sprayed onto or make contact with. These tend to be based on “naturally-occurring” active ingredients, such as acetic acid and natural fatty acids.
Systemic weedkillers, that also kill the roots can also be used.
To ensure weedkillers work more effectively:
- Spray the leaves when the plants are actively growing; this is mainly from March/April to September/October. Contact weedkillers will have some effect if used during the colder weather in winter.
- Use a fine spray to thoroughly coat the leaves in small droplets.
- During the summer, spray in the evening to prevent the spray evaporating and to give maximum time for the spray to work. In spring or if overnight dew is forecast, spray earlier in the day to allow the spray to dry before dew falls.
Weedkillers (except lawn weedkillers) are total weedkillers – that is they will damage or kill any plants whose leaves they are sprayed onto. Make sure you keep the spray off wanted plants – including lawns – and, if necessary protect plants by covering with polythene or similar when spraying.
Use weedkillers safely. Always read the label and product information before use.