Slender rats tail grasses

03 May 2022

A prevalent native grass this season

Tablelands Telegraph - May 2022

One of the most frequent enquiries, and a popular question at my recent pasture walks, has been about the slender rats tail grasses. There are two very similar native species which go by this name (Sporobolus creber and S. elongatus), which are also known as Parramatta grass.

They are a common warm season perennial grasses with seedhead stems making them up to 80-120cm in height. The seedheads are distinctively long and narrow with very small brown-black seeds in late summer. If you look closely, the seeds are on short branches and are pressed against the main stem. The main stem is visible along much of its length. The leaves are sparse and often pale green, hairless, tough, and waxy.

These species of grasses are more common and prevalent in years with good summer rainfall. They usually flower from spring through to summer. More likely to be found in native based pastures, they can colonise degraded sown pastures quickly – especially in lighter textured and lower fertility soils. They are often found in pastures with the native red grass (Bothriochloa macra).

Slender rats tail grasses have moderate grazing value when young, however the stem is fibrous during the growing season and is often very low in palatability. Hence, they are overlooked by the grazing animal. In addition, this year many of our pastures are very grassy and – coupled with lower stocking of animals – these species have become very prevalent and are being noticed.

They are a warm season perennial grass, so managing this plant in a diverse pasture is complicated. It is more often a minor plant in a pasture. However, if they have become a monoculture, then a pasture plan is worth considering. This plan will involve discussion on soil type and fertility, land class and grazing management. Part of the discussion should also factor in the species’ warm season nature and susceptibility to frost. Therefore, an understanding of the other species in the paddock, especially the cool season annuals, needs to be part of the plan.

Before you remove or change your perennial native grass-based pastures, it is important to consider that native groundcover is subject to the NSW Land Management Framework and other NSW and federal biodiversity conservation laws and regulations, unless otherwise authorised. Landholders are encouraged to contact their Local Land Services office for advice on their specific circumstances.

It is worth noting that there are other porobolus grasses that are introduced. An example is African Paramatta grass (S. africanus), a shorter plant which looks very black in the seedhead late in the season. It is often infected with ergot (a fungus) which makes the seedhead look sooty black. It is usually found around roadsides, yards and sheds.

The major weed Giant Parramatta Grass (GPG) (S. fertilis) is uncommon in the Central Tablelands area. It is worth seeking an identification if you think that you have this grass. It is highly competitive, invasive and unpalatable. I find it flowers later than the native porobolus species and is a larger plant overall. One of the key recognition features for GPG is that the stems at the base of the plant are flattened (compared to the native species which are rounded) and the seedhead is thick with seed without much stem visible.

Note: GPG is a PREVENTION management outcome in our Central Tablelands Regional Strategic Weed Management Plan and if you think you have it you must report to the local council weed officers who will work with you to confirm identification and support eradication of GPG from the site.