Coarse grasses in lawns

Coarse grasses may look different to traditional lawn species but they are great for supporting wildlife and boosting the biodiversity of your garden. Most gardeners tolerate or welcome them, but those wanting a uniform, immaculate lawn are likely to consider them weeds.

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Quick facts

  • Common types of coarse grass include annual meadow grass, Yorkshire fog and couch grass  
  • They are sometimes referred to as weed grasses 
  • Coarse grasses often appear as patches in fine lawns, where the leaf texture of desired grasses (often fescues and bents) blend seamlessly 
  • Caterpillars of various butterflies feed on the leaves of coarse grasses    
  • In winter, coarse grasses often become more prevalent, as many cope with cold weather better than fine grasses   
  • If you need to control coarse grasses in lawns, non-chemical methods take time but are effective

What do coarse grasses look like?

If there are obvious patches of grass that differ in colour, texture or height to surrounding fine turf, then you probably have coarse grass in your lawn. Identifying the type of coarse grass you have isn't essential, but it might help you decide if you want to keep or remove it and, if you chose to remove it, how best to do so. The descriptions and images below will help you identify three of the most common coarse grasses:  

Annual meadow grass (Poa annua) is a very common, native coarse grass. Its leaves grow out horizontally from a central point, reaching a spread of about 20cm (8in). They are usually light green, but there are also forms with dark purple leaves. Branching flower spikes that form a roughly triangular outline have pale green flowers at the tips. These can appear at any time of year. Its seed is oval, light brown and about 2mm long.  

Depending on growing conditions, it can be annual, ephemeral (completing its life cycle in less than one year), or occasionally perennial. It has shallow, fibrous roots and can reach a height of 30cm (12in), but is generally much shorter in regularly mown lawns.

Yorkshire fog (Holcus lanatus) is a native perennial grass. It forms dense clumps of soft, hairy, upright stems and grows to 1m (3½ft) tall. Its flat leaves are greyish-green. Purplish-red tinged flower spikes appear in summer, followed by greyish-pink seedheads. Runners (stems that produce roots) help it spread.

Couch grass (Elymus repens) is a fast growing, native perennial grass. Stems with flat, green leaves can grow over 1m (3½ft) tall. Upright, unbranched flower spikes with yellowish-green flowers appear in late summer. It forms a dense network of pale rhizomes (underground stems) with thinner, fibrous feeding roots.  

Couch grass can be problematic in borders as well as lawns; for more information see our page on controlling couch grass.

Are coarse grasses weeds?

Many coarse grasses, such as the three above, are native to the UK and are great plants for wildlife, particularly butterflies. Coarse grasses are great additions to wildflower meadows, adding height with their swishing seedheads. Even when allowed to grow in a regularly mown domestic lawn, coarse grasses help increase its biodiversity: 

  • Caterpillars of gatekeeper butterflies feed on annual meadow grass and couch grass. 
  • Caterpillars of speckled wood butterflies enjoy couch grass and Yorkshire fog.  
  • Caterpillars of the small skipper butterfly and wall brown butterfly also feed on Yorkshire fog.  
  • Garden birds feed on the seeds of coarse grasses. Annual meadow grass is particularly valuable as a source of winter food for finches. 

A gatekeeper butterfly
A small skipper butterfly
However, gardeners intent on maintaining the neatness and uniformity of an immaculate, fine lawn are likely to consider coarse grasses as weeds.
What is a weed?

The term ‘weed’ describes a plant that is growing where it isn’t wanted. Weeds usually thrive in average garden conditions, reproducing and spreading easily. It is up to you to decide what you call a weed and what you choose to retain or remove.

Frequently asked questions about controlling coarse grasses in lawns

Here are our answers to your most common questions about dealing with coarse grasses in lawns:    

How invasive are coarse grasses?  

Coarse grasses use a few methods to increase their spread. Annual meadow grass quickly colonises bare patches of fertile soil by seed. Its success in lawns is due to its ability to flower and seed, below the height of mower blades, year-round. Wind, water, animals or human activity can spread the seed.  

Some coarse grasses, such as Yorkshire fog, also spread by runners (rooting stems) that grow outwards from the main clump. If these grow over bare soil, or into an area where fine grass species are weak or sparse, they will send down roots, increasing the size of the clump.  

Unlike the others, couch grass spreads primarily by rhizomes (underground stems) and can regenerate from small sections of rhizome. It is less likely to spread by seed. See our page on couch grass for more details.  

Do I need to get rid of coarse grasses in lawns?    

No – allowing course grasses to grow in your lawn is a great way to boost the biodiversity of your garden. As they look green and can be walked on, played on and mown along with traditional lawn species, there is no need to remove them from your sward. They are particularly attractive, and more beneficial to wildlife, if allowed to grow tall and set seed, so there is no need to remove them from wildflower meadows or species-rich lawns either. 

You will only need to get rid of course grasses if you want an immaculate, less biodiverse, fine lawn.

Coarse grasses add interest to meadows and species-rich lawns 
Did you know?

Maintaining an immaculate, fine lawn is labour intensive, reduces biodiversity in a garden, and often involves applications of fertilisers and pesticides that are harmful to the environment. Perceptions of lawns are changing, and gardeners are embracing the benefits of species-rich lawns, reflected by the popularity of initiatives such as No Mow May and Let it Bloom June.

What is the easiest way to kill coarse grasses?    

If you have coarse grasses growing in your lawn and they cannot be tolerated, there are methods of controlling them:  

  • Improve the health of your lawn – coarse grasses are less able to establish in dense, healthy lawns. Follow a programme of lawn maintenance in spring/summer and autumn to boost the vigour of your lawn. If patches of your lawn are struggling, overseed with a mix to suit the growing conditions.  
  • Mow regularly – this will prevent some of the taller coarse grasses flowering and setting seed. Fine grasses are better adapted to tolerate regular cutting, whereas it will weaken coarse grasses. Use a collection box to remove the clippings, which may include coarse grass seed.  
  • Avoid frequent watering – watering little and often during dry spells benefits coarse grasses, like annual meadow grass, that have shallow root systems. As lawn grasses are generally drought tolerant, there is no need to water an established lawn; even if it becomes brown during hot, dry weather, it will usually recover following a decent amount of rain. 
  • Fork out plants – insert a hand fork under the main clump or rooted sections of stem and lift out the roots. This is a good, easy option for quick results on small areas of lawn. September is a good month to remove coarse grasses by hand, as it will reduce the population before winter (a season when they can thrive) and you can re-seed patches of bare soil straight away.    

Top Tip

Don’t add runners, rhizomes or seed from coarse grasses to your home compost bin, as it may not reach high enough temperatures to kill them. Instead, put them in your council green waste recycling bin or take them to your local recycling site.

Should I use weedkiller?   

No – selective lawn weedkillers are not effective on coarse grasses and non-selective weedkillers will kill all grass species, including those you wish to grow. As non-chemical control methods are effective, even if time-consuming on large lawns, there is no need to use a weedkiller.  

For more information, see our page on Weeds: non-chemical controls

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