Updated: May 26
Have you noticed different types of grasses within your lawn recently? With the welcome return of good growing conditions comes the seasonal burst of annual meadow grass (Poa Annua) along with other seasonal shallow-rooting meadow grasses. These grasses can lead to a lawn appearing patchy and discoloured with several grass types present. The management of weed grasses is an ongoing battle for greenkeepers and groundsmen. In the absence of a chemical control that will differentiate between difference types of grass - management is the key word.
Where are these Weed Grasses coming from?
As with many seeds, weed grasses can be spread by birds, and can lie dormant in the soil for a number of years. Even turf growers will not guarantee against some annual meadow grass - it can be that invasive. Cheaper top soils and top dressing may contain seeds if not sterilised.
Poa (as known in short by greenkeepers and groundsmen) is a very different grass as it has a very short lifecycle. This plant is shallow rooting; it knows its days are numbered should we get a dry spell and works to produce seed heads as quickly as possible, allowing this weed grass to spread further. Unfortunately, the entry point of weed grasses cannot be stopped but as ever with any other weed or moss, maintaining a dense grass cover through regular lawn treatment and occasional lawn renovation will make your lawn less susceptible and easier to manage.
Our Top Tips for the Control of Coarse Grasses
Mowing more frequently at a height of 25-35mm will complete a dual job of helping the desirable grasses in your lawn to thicken and thrive and allow you to mow out a number of the seed heads being produced.
Verticutting / Light Summer Scarifying
We typically advise against the scarifying of lawns through summer months, but this depends on the severity of the work. Many domestic lawn rake' type machines can be useful tools in combatting meadow grasses to mechanically (or manually via a rake) remove or weaken them. This light thatch removal will aid desirable grasses. You can see a verticutter cassette in action below thanks to Allett Mowers and our friends Robbie Lynn at Premier Lawns.
Stress it Out?
With Poa being a shallow rooting grass dependent on rainfall, be sure that you're not over-watering your lawn. Not watering at all while Poa is present will create less favourable conditions for it. Dropping your mowing height is a consideration as a one-off in order to capture as many seed heads as possible. Take care as this will likely lead to your lawn looking worse before it gets better. Be aware that doing this will not capture all seeds and it wouldn't be worth scalping your lawn to achieve a minimal gain.
As we recommend with difficult to control weeds such as Speedwell, taking a knife to areas of turf is a good option. It is important that the whole of the plant is removed, and maybe more applicable to rough stalked meadow grass as annual meadow grass will have already dropped seeds.
Encourage Desirable Grasses with Correct Fertilisers
Poa requires adequate levels of phosphorous for germination and flowering, and also enjoys an acidic soil. Be sure that what is going into your lawn is working in your favour. We apply no phosphorous to our lawns with our early-summer treatments and our fertilisers are slightly acidic which promotes finer grasses slightly. Our Lawn Care Treatment Programme is full of marginal gains!
A Patchwork Problem?
We need to promote better growing conditions for the rye and fescue grasses that we wish to promote for an attractive lawn - there could be a number of reasons as to why this isn't successful for a number of reasons from leatherjackets to excessive shade. Lawn Renovation is a process of:
Scarifying the lawn aggressively - thereby clearing out a great deal of shallow rooting grasses, thatch and moss
Mowing the lawn as a lower than normal height, hoovering out debris
Aerating the lawn - creating better soil conditions for desirable grasses
Overseeding the lawn, improving the % of desirable grasses.
Weed Grasses - Our Thoughts
It is worth noting that weed grasses due to being shallow rooting can only thrive at certain times of year in certain conditions. Lawns are made up of many grass types with different strengths and weaknesses when it comes to colour, density and tolerance of close mowing and drought conditions. Much like with plants in your garden, difference grasses will thrive under differing conditions.
Weed grasses cannot be eradicated. Poa will grow at very low heights of cut and in nearly all soils when conditions allow - even on golf and bowling greens. Rather than seek unrealistic complete control, we should look to manage and embrace annual meadow grass in particular. This should be through caring for our lawns with a sustainable fertiliser programme in combination with mechanical / manual work for the best possible lawn health. Our efforts targeting weed grasses should be sustainable as they are here to stay! If the desirable grasses in your lawn need a lift, or if the volume of weed grasses demand more aggressive work, you can speak to us on 01827 826123 for more information on how we can help, or complete our contact form.