Foreign grasses can invade lawns in a number of ways — from dormant seeds already in the soil to new seeds spread by wind, birds, or even contaminated lawnmowers. Some varieties grow all year round, while others appear only in certain seasons. While many foreign grasses can be controlled with selective weed killers, others are much harder to treat and may require alternative solutions.
Below are some of the most common types of foreign grasses that invade lawns.
Summer grasses are a group of warm-season grass weeds that appear only during the hotter months. With many different varieties, they can invade both lawns and gardens. They are most common in areas where the lawn has thin or patchy grass cover, and are especially prevalent in newly sown spring or summer lawns where grass density is still developing. Summer grasses are often carried in by the wind, quickly establishing even in a well-maintained lawn. Once present, they often return in greater numbers the following summer.
Summer grass can be controlled using Meso. If you experienced a heavy infestation in the previous season, we recommend applying a pre-emergent spray such as Meso or Etho-Pro before summer begins. This helps to reduce the number of seeds in the soil that will germinate as temperatures rise.
Paspalum is a hardy grass weed that is often mistaken for summer grass due to its similar leaf shape. However, unlike summer grass, Paspalum persists beyond summer and can even appear during cooler months. It is very resilient and grows actively in the warmer season, producing tall, tough seed heads. These seed heads are usually much taller and stronger than those of summer grass, making them easy to identify once mature.
Paspalum can be controlled with Haloxyfop on Fine Fescue lawns only. In lawns blended with Fine Fescue, it can be spot-sprayed with caution. Haloxyfop cannot be used on Turf Rye, Tall Fescue, or Kikuyu lawns. In these cases, Paspalum may need to be removed by physically cutting it out and repairing the area with grass seed or instant lawn.
Poa Annua, commonly known as Poa, is one of the most common turf weeds and thrives in wet conditions. It typically appears during winter and spring and can be identified by its lighter green colour, faster growth, and distinctive whitish seed head that sits close to the ground. Because Poa is able to drop seed between mowing, it can spread quickly. It also responds strongly to fertiliser, so applying general fertiliser during this period will worsen the problem.
Poa is shallow-rooted and usually dies off once warmer weather arrives. If left untreated, this dieback can leave large bare patches in your lawn at the start of summer.
To control Poa, focus on maintaining a thick, healthy sward of grass heading into winter. Pendi-Pro fertiliser can be applied as it includes a herbicide and pre-emergent properties to inhibit the seeding and spread of Poa. Etho-Pro is an effective option for chemical control on Rye and Tall Fescue lawns.
Yorkshire Fog, also known as Fog Grass, is a desirable pasture grass but considered unwanted in home lawns. It has very hairy, broad leaves, giving it a soft, velvety texture. The leaves feature purple and white striped veins at their base, and the grass can produce a distinct, fluffy seed head – although this is rarely seen on a mowed lawn.
Yorkshire Fog can be effectively treated with Meso. Haloxyfop can also be used on Fine Fescue lawns only and spot sprayed with caution on lawns blended with Fine Fescue. Haloxyfop cannot be used on Turf Rye, Tall Fescue or Kikuyu lawns.
Kikuyu grass is a vigorous, warm-season grass that is loved by some but considered an invasive weed by others. It thrives in hot weather, often spreading rapidly when other lawn species are struggling, and stays alive all year round, though it can become dormant during frosts.
While Kikuyu grass can be difficult to eradicate, it can be successfully controlled using Grazon or Meso.
Once per year, usually from spring to early summer, some desirable lawn grasses will attempt to produce seed heads. When these seed heads are regularly cut down by mowing, they grow horizontally instead, creating patches of coarse, untidy-looking grass for a short period.
There is no need to spray or remove this grass. It is healthy, desirable grass, and its appearance will return to normal once the seeding period ends.