We've put together some examples of common lawn weeds to help you identify any you may have growing in your lawn, as well as some top tips for dealing with them.
common lawn weeds
Weeds are persistent and able to survive in the harshest of growing conditions, so it's no wonder when they land on a lush green lawn they establish quickly. Weeds can be wind blown, bought in with new top soil, dropped by birds, or just lying dormant in the soil until conditions are ideal to germinate.
Regular mowing, watering and feeding is the best way to keep weeds at bay, but sometimes there are other factors such as hot, dry summers, excessive wear and foot traffic, mowing the lawn on too low setting, and insufficient watering that give weeds an opening.
There are three main types of invading weeds. All are great indicators as to what is happening in the soil below your lawn.
- Broadleaf weeds – flat broad leaves of varying sizes and habits, for example dandelion, clover, creeping oxalis, prickle weed (Onehunga weed) and dock. The presence of broadleaf weeds is often an indication that the soil is acidic and likely needs an application of lime to help adjust the pH, lawns prefer a neutral pH around 6-7. This is best applied in autumn and/or early spring.
- Grasses – similar in appearance to lawn turf grasses but fast growing and invasive, some have underground creeping stolons such as couch, twitch, kikuyu; others clumping such as paspalum, summer grass, crab grass and Poa annua.
- Sedges – also similar to lawn turf grasses in appearance, often called ‘nutgrass’ or ‘nutsedge’, a perennial grass with shiny leaves and a groove down the centre that grow in clumps, loves damp soils.
Dock
What is dock?
- Low lying broadleaf oval or heart-shaped leaves that avoid mower blades.
- Perennial weed with a long tap root that competes with grass for nutrients and water.
- Thrives in compacted soils.
How to fix
- Remove by hand ensuring the whole tap root is removed.
- Spray with a selective herbicide that controls broadleaf weeds.
- Feed the lawn in spring and autumn with a balanced Tui Lawn Fertiliser to encourage new growth.
- Aerate to improve soil drainage
Buffalo grass
What is buffalo grass?
- A creeping perennial summer grass that is prevalent in coastal areas.
- Dullish-green coarse textured invasive grass that forms thick mats.
- Tolerates dry and damp conditions, sun and shade, and is frost tender.
How to fix
- Spot spray with a non-selective weedkiller.
- Hand weeding isn’t effective as pieces remain in the soil and it returns.
- Regular watering, feeding and mowing will encourage lawn growth and crowd out invading grasses.
Clover
What is clover?
- Low growing mats with three rounded leaflets, with white or pinkish clover flowers.
- Often spreads in thinner, under fed parts of the lawn.
- Clover isn’t all bad as it fixes nitrogen from the soil and attracts bees to the garden.
How to fix
- Improve lawn vigour with regular feeding using a Tui LawnForce® lawn fertiliser so the grass can out compete clover.
- Spot treat small patches with a selective broadleaf lawn weed spray.
- For heavy infestations, treat the whole lawn in spring or autumn. Repair patches with our guide on patching an existing lawn.
Couch
Couch (pictured), kikuyu and twitch
- Fast spreading creeping grasses that look different to the rest of the lawn.
- Spreads via runners above or below ground, quickly forming dense patches that are a different colour or texture to the rest of the lawn.
How to fix
- Hard to control by mowing alone.
- Can be removed manually but the risk of spread is high as each remaining root will grow.
- As they are grasses, selective broadleaf lawn sprays won't work. Spot spray affected patches with a non-selective systemic weedkiller - note this will kill off surrounding grass as well.
Dandelion
Dandelion and Catsear (false dandelion)
- Rosettes of leaves flat to the soil.
- Bright yellow daisy like flowers on stems; fluffy seed heads on dandelion.
- Deep taproot that can regrow if you only remove the top.
How to fix
- Hand dig individual plants, making sure you remove as much root as possible.
- For larger numbers, apply a selective broadleaf lawn weed spray while plants are actively growing.
- Once the weeds brown off, rake out and follow our guide on patching an existing lawn.
Hydrocotyle
Hydrocotyle
- Mat-forming, creeping, broadleaf weed 1cm in diameter that smothers lawns.
- Prevalent in poorly drained, damp, shaded areas of the lawn.
- Can appear in lawns that are overwatered.
How to fix
- Improve soil drainage by aerating with spikes or a garden fork.
- Reduce watering and improve light penetration by pruning overhanging trees.
- Use a selective herbicide specific to hydrocotyle in spring and autumn.
- If hand weeding, make sure the creeping stolons are removed otherwise it will reappear.
Plantain
Plantain
- Flat growing weed with rosette shaped leaves and tall flower spikes.
- Thrives in damp, compacted soils with low nutrient levels.
- A resilient weed that tolerates foot traffic, wear and mowing.
How to fix
- Improve soil aeration, soil fertility and drainage.
- Feed in spring and autumn with a Tui LawnForce® lawn fertiliser to encourage dense grass growth and reduce re-invasion.
- Remove by hand or control using a selective broadleaf herbicide for lawns.
Poa annua
Poa annua / annual poa
- Small tufts of pale green grass with dainty seed heads that look different to the rest of the lawn.
- Annual weed that seeds prolifically.
- Often appears in cool, damp spots or where the lawn is thin.
How to fix
- Mow regularly to prevent seeding, and collect clippings.
- Improve drainage and reduce compaction; overseed thin patches to reduce bare soil.
- Where infestations are severe, treat with with a non-selective systemic weedkiller - note this will kill off surrounding grass as well. Expert tip: Pre-emergent herbicides used at the time of sowing seed are effective in controlling Poa annua.
Prickle weed
Onehunga (prickle) Weed
- Flat low growing small fern-like foliage that spreads.
- Small creamy white flowers produce sharp prickle seed heads in summer.
- Seeds germinate in autumn, lay dormant over winter.
How to fix
- Best controlled in autumn and early spring with a selective herbicide for lawns.
- Spring timing is crucial, this must be done before flowering starts.
- Easy to remove by hand weeding.
Summer (crab) grass
Summer Grass / Crab grass
- A group of flat growing creeping annual grass weeds similar in appearance to paspalum.
- Light green in appearance with coarse textured leaves, forked (crowsfoot) seed heads in summer.
- Frost tender, so more prevalent in the North Island.
- Appears in sparse drought stressed lawns.
How to fix
- Consistently water the lawn and keep it well maintained through the hot summer months.
- Mow lawns on a high setting to encourage dense lawn growth.
- Feed the lawn with a Tui LawnForce® lawn fertiliser in spring and autumn.
- Don’t allow summer grass to seed, hand weed or spot spray with a non selective herbicide.
Scotch thistle
Thistles (Scotch thistle, California thistle)
- Flat, rosette shaped weeds with prickles covering the leaves that seldom flower in lawns.
- Thistles appear in summer in sparse, drought stressed, compacted, infertile lawns.
- Wind blown seed easily germinates in lawns, they are unaffected by mowing.
How to fix
- Aerate the soil with spikes on shoes or with a garden fork to improve drainage.
- Mow on a high setting to encourage dense grass growth.
- Hand weed, making sure the whole tap root is removed.
- Water consistently to encourage dense growth, and feed throughout the season with Tui LawnForce® lawn fertiliser.
Sedge
Sedge
- Grass-like shiny green leaves that grow in clumps.
- V shaped leaves with serrated edges.
- Found in damp infertile soils especially in shady areas.
How to fix
- Improve drainage, aerate the soil with spikes on shoes or with a garden fork.
- Hard to hand weed, dig down to remove the whole root, otherwise it will re-sprout.
- Spot treat with a non-selective herbicide, repeat applications may be required.
- Feed in spring and autumn with Tui LawnForce® lawn fertiliser to promote dense grass growth and reduce re invasion.
General weed control tips for lawns
The presence of broadleaf weeds in lawns is often a sign that the soil is acid and likely needs an application of lime to adjust the pH, this is best done in autumn and / or early spring. Regular mowing, watering and feeding is usually enough to keep weeds at bay, but sometimes there are other factors such as hot dry summers and insufficient watering that give weeds an opening. The best times to control broadleaf weeds is in lawns is spring and autumn when lawns are actively growing, using a selective herbicide or a systemic weedkiller.
Selective herbicides are specially formulated to control broadleaf weeds but do not harm grass (except they may burn some fine turf fescues, do a test patch first) so can confidently be sprayed on the lawn, the weeds yellow and die off after approximately 7 days. Once browned off, dead patches can be raked out, lawn preparation mix added to the patch and resown with a similar looking grass seed to the existing lawn. For example, a lot of Ready Lawn is Tall Fescue, so resow the patches with Tui LawnForce® Superstrike® Tall Fescue Lawn Seed.
It isn’t only broadleaf weeds that can be a problem though, for example if wanting to remove couch, twitch, kikuyu or Poa annua a selective herbicide is not effective because they are grasses. A non-residual systemic herbicide will need to be used to spot spray the area, but this will also kill off the existing grass, so only spray patches that are affected with these invasive grasses. Rake them out and patch as per above. Sometimes repeat sprays of selective herbicides may be required for more persistent or perennial weeds.
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