paspalum dilatatum or crowngrass collar hairs
Paspalum leaf collar hairs
paspalum aka crowngrass or dallisgrass
paspalum dilatatum or dallisgrass flower spikelets
 

Paspalum (Paspalum dilatatum)

Paspalum (Paspalum dilatatum), is also known as Dallisgrass or Crowngrass. It is a persistent tufted warm-season grass that grows up to 1.5 m tall. Queensland, New South Wales, Victoria, West Australia and South Australia class this as an environmental weed.

After you finish reading this, you will be able to:

  • Identify Paspalum, Dallisgrass and Crowngrass.

  • Know where you are likely to find this weed grass and

  • Know the best cultural and chemical options to control Paspalum.

Paspalum is a major weed of turf and reproduces by both seed and via rhizomes. Plants germinate in the Spring and early Summer, and flower from mid-Summer to early Autumn. Mature Paspalum has smooth sheaths and a tall membranous ligule, up to 5mm in height.

The simple way to identify this grass weed, is to look for a purple base or look at the root system below the soil surface. Paspalum dilatatum grows from short, thick rhizomes underneath the ground. The joints (internodes) of these rhizomes, look like tight, concentric circles of growth layered together.

Dallisgrass has strong, prostrate tillers that do not root at the nodes.

In cool areas like the Southern Highlands of New South Wales and the ACT, Paspalum becomes dormant in winter. However, even though it dies back, the roots are still alive, and the weed will return with warm weather in Spring.

How to Identify Paspalum.

Flower: The flower head divides into a few branches, which are lined with beadlike pairs of green to purple spikelets.

Height: It grows up to 1.5 metres in height.

Leaf length: Leaves are up to 35 cm long.

Leaf width: Leaves are up to 2.5 cm wide.

Reproduction: Paspalum reproduces by seeds, which disperse by the wind, in water, by pets, or on machinery.

Comments: The leaves are mainly hairless, have a folded base, and have a noticeable mid vein. Seed heads are at the tips of upright flowering stems and have 2-11 branches. These are 2.5-11cm long, and are arranged alternatively along the main stem, being covered in hairs.

Habitat: Crowngrass is a major turf weed, and is a common weed of gardens, lawns, parks, verges, disturbed sites, and waste areas, in tropical, sub-tropical and temperate regions. While it can grow in many habitats, it prefers moist conditions and it is an indicator weed of compacted soils. Please feel free to check out our weed ID chart.

 

 

Paspalum.

When we refer to Paspalum in Australia we are referring to three species of Paspalum that are common turf weeds.

These are all warm season C4 grass weeds, and you can see them as clumps of coarse leaved grass in the summer. All of these are very difficult to pull out of the ground by hand.

In the spring once temperatures warm up, Paspalum produces yellow-green leaves that look like Summer grass, and as temperatures continue to increase the leaves take on a darker colour and develop into tough clumps of grass.

Over time these clumps become bigger but do not form mats like couch grass. This increase in size occurs due to the presence of rhizomes,

Seedheads form in late summer, and are you see these infrequently cut turf.

Paspalum seeds form in rows on finger-like spikes and are noticeably shiny, whitish, flat, and oval-shaped.

Paspalum grows in soils of all types and has excellent heat and drought tolerance, but browns off after a few frosts and becomes dormant.

Once the frost-killed leaves die, the clumps disappear, but will return as weather warms in mid-to-late spring. In Spring, new leaves grow from dormant buds on stem bases.

 

 
 

How to remove Paspalum from your lawn.

There are cultural and chemical options for Paspalum or Crowngrass control in turf.

 

Cultural control.

The key to prevent Paspalum, is to maintain a thick, health turf cover with no bare spots. This means that you need to cut turf at the right height of cut and feed it properly. The most effective way to get rid of existing clumps of Dallisgrass is to dig out each clump by hand or with a shovel. But, as it has tough, thick roots mature plants are difficult to remove.

When you dig up a plant, you must ensure that you remove all the rhizomes from the soil. If you don’t do this new plants are able to re-establish if you leave any rhizomes behind.

Hand digging is a realistic approach to counter Paspalum when clump numbers are small, and in early summer before it produces seedheads.

Pre-emergent control.

There are only a few pre-emergents for dallisgrass, and these vary in longevity and safety. Good options to consider include Onset 10GR or Barricade Herbicide.

You apply Barricade at 2-4L/Ha to give up to 6 months control. If you use this at lower rates and make split applications, you need to make another application 2-3 months later. Freehand is only for use on warm season turfgrass and you use this at 2Kg/100m2.

The yearly use of Dimension, which targets summer grass, may have good pre-activity on Paspalum.

Post-Emergent Control.

With chemical control, the best results for Paspalum dilatatum control, are if you carry out treatment before seed sets. Only MSMA (ProForce Geronimo) is known to properly control Paspalum.

MSMA causes a lot of yellowing and can cause severe injury if you apply it in hot summer weather.  As a result spot-treating clumps with MSMA is best.

Spot-treatments localize yellowing and potential turf injury, and will also giving better control of Crowngrass. Normally, it needs at least two spot-applications of MSMA over 7-10 days for good control of Dallisgrass.

When you use MSMA, you can increase turf safety if you increase the water volume, use half rates and make frequent applications (i.e., half rates need to be applied on 5-7 day intervals at least three times) to get good Dallisgrass control and increase its safety.

 

 

Pylex.

Another product that suppresses Paspalum dilatatum, is Pylex but in Australia this not registered for this. Spot applications of Pylex burn-down foliage and stop seedheads, but plants are likely to survive.

A burn-down approach is a long term approach. and burn-downs will improve how the turf competes.

Realise that the clumps have been around for only a year, will have produced thousands of seed.

Hence, the use of Onset 10GR in a Spring “Summer grass” application timing. So we recommend you use Onset 10GR where you are targeting summer grass (or Crowsfoot) and Paspalum.

If you want to carry out non-selective control of Crowngrass, then Rapid Fire is your go to. However, we recommend you add a tank buffer/adjuvant. A product like Manta Ray ensures good spray cover of paspalum, and counters alkaline hydrolysis.

 

In summary we recommend the use of Geronimo for Crowngrass control. But, take care if you use this as it is not selective on all grass types. This means it is very important to read the label.