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 read this, you will be able to:
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Identify Paspalum, Dallisgrass and Crowngrass.
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Know where you are likely to find this weed grass and
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Know the best cultural and chemical options to control Paspalum (Paspalum dilatatum).
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 5 mm high.
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 returns with warm weather in the Spring.
How to Identify Paspalum.
Flower: The flower head of Paspalum divides into a few branches, which are lined with beadlike pairs of green to purple spikelets.
Height: It grows up to 1.5 metres tall.
Leaf length: The leaves of Paspalum are up to 35 cm long and grey to green in colour. It has a few sparse hairs on the leaf collar, and hairs are also sometimes present at the base of the leaf blade.
Leaf width: The 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. This distinctive mid-rib helps distinguish paspalum from other coarse grass weeds like Summer grass (Digitaria spp.).
The seed heads of Paspalum are at the tips of upright flowering stems and have 2 to 11 branches. They are 2.5 to 11 cm long, arranged alternatively along the main stem, and 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 or Crowngrass that are common turf weeds.
These are all warm season C4 grass weeds, and you see them as clumps of coarse leaved grass in the Summer months. 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. Seedheads of Paspalum form in late Summer, and you see these on infrequently cut turf.
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 the 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 of Paspalum.
- Maintain healthy turf. The key to prevent Paspalum dilatatum, 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.
- Hand removal. 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 it up, you must ensure that you remove all the rhizomes from the soil. If you don’t do this Paspalum is able to re-grow.
Hand digging is a realistic approach to counter Paspalum when clump numbers are small, and in the early Summer before it produces seedheads.
- Fix the drainage. Paspalum favours poorly drained areas, so if you fix the drainage it goes some way towards managing this weed grass.
- Paspalum tolerates close mowing so this is not an effective way to control it.
Pre-emergent control of Paspalum.
There are only a few pre-emergents for Dallisgrass, and these vary in longevity and safety. None of these control existing Paspalum plants.
Do realise that even if plants have only been around for a year, Dallisgrass will already have produced thousands of seed.
Good options to consider include Onset 10GR, Freehand or Barricade Herbicide. The use of Onset 10GR in a Spring “Summer grass” application timing for summer grass (or Crowsfoot) also controls Paspalum.
Barricade at 2-4 L/Ha gives up to 6 months control of Crowngrass. If you use this at lower rates and make split applications, you need to make another application 2 to 3 months later.
Freehand herbicide is only for use on warm season turf grass and you use this at 2 Kg/100m2.
The yearly use of Dimension, which targets summer grass, may also have good pre-activity on Paspalum.
Post-Emergent Control of Paspalum.
With post emergent control, the best results for Paspalum dilatatum control, are:
- If you carry out treatment before the seed sets.
- You make repeat applications of a herbicide.
- Apply Tribute with an MSO instead of a nonionic surfactant (NIS).
Warm Season Turf Options.
All of the following you can use on warm season turf.
- MSMA . Historically, repeat applications of organic arsenicals (MSMA or DSMA) have been used with variable results. MSMA causes a lot of yellowing and can cause severe injury if you apply it in hot weather. As a result the best results are if you spot-treat clumps with MSMA, rather than broadcast spray.
Spot-treatments localize yellowing and any potential turf injury, whilst giving better control of Crowngrass. Normally, it needs at least two spot-applications of MSMA over 7 to 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 to 7 day intervals at least three times) to get good Dallisgrass control.
Tribute Selective Herbicide.
A good rule of thumb is to apply when the average 24-hour air temperature falls below 22°C for at least three consecutive days.
Non Selective Control.
If you want to carry out non-selective control of Crowngrass, then Rapid Fire 800 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 the effects of alkaline hydrolysis.
If you spot treat Paspalum with Glyphosate use a spray nozzle that produces coarse spray droplets as this reduces drift onto desirable turf grass.
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.
