Dallis Grass
Paspalum dilatatum
NEMBA category
English: Dallis Grass, Dallisgrass, Sticky Heads, Water Grass, Paspalum, Common Paspalum, Bastard Millet Grass, Golden Crown, Golden Crown Grass, Hairy-flowered Paspalum, Large Water Grass, Large Waterseed, Large Waterseed Paspalum, Millet Grass, Water Grass
Afrikaans: Breësaadgras, Breësaadvleigras, Breëvleigras, Dallisgras, Bankrotkweek, Gewone Paspalum Gras, Paspalatum, Paspalatum Gras, Paspalum, Paspalum Gras, Paspalumgras, Water Gras, Watergras
Historical scientific names: Paspalum moluccanum, Paspalum ovatum
Misapplied scientific names: Paspalum notatum, Paspalum urvillei
Paspalum dilatatum. commonly known as Dallis Grass, is a tough, clump-forming perennial grass that forms dense tufts of long, narrow, green leaves. Its most distinctive feature is its flower stalks, which stand upright and have several widely spaced, drooping branches (racemes) with small, sticky-looking, hairy seed heads.
This grass is often found along roadsides, in ditches, and in disturbed areas, and while sometimes used for pasture, it can quickly become an invasive weed, especially in damp conditions.
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Origin:
Native to South America, specifically Brazil, Argentina, Bolivia, Chile, Paraguay, and Uruguay.
Distinguishing features:
Dense, coarse clumps: Forms robust, tufted bunches of grass.
Long, narrow leaves: Green, often folded at the base, and mostly hairless.
"Sticky" seed heads: Flower stalks have widely spaced, drooping branches with spikelets that often feel sticky due to a sugary exudate or fungal infection (ergot).
Short rhizomes: Spreads via short, underground stems, contributing to its dense clumping habit.
Prefers moist, disturbed areas: Commonly found along roadsides, ditches, and in damp, disturbed soil.
Overall appearance:
A robust, perennial grass that grows in coarse, spreading tufts or clumps. It has a leafy, somewhat untidy appearance, especially when its flower stalks with their distinctive seed heads emerge above the foliage.
Height:
Flowering stems (culms) typically grow between 0.5 and 1.5 metres tall, but can sometimes reach up to 1.8 metres.
Width:
Forms dense clumps, with individual plants spreading up to 0.5 metres wide, but colonies can cover much larger areas due to spreading rhizomes and prolific seeding.
Leaves:
Mainly basal, growing from the base of the plant in a tuft. The leaf blades are linear to lance-shaped, 10 to 45 centimetres long and 0.3 to 1.2 centimetres wide. They are typically green, often folded at the base, and mostly hairless, though the lower leaf sheaths might have a few hairs. The ligule (a small membrane at the junction of the leaf blade and sheath) is membranous.
Flowers:
The flowers are tiny, inconspicuous, and contained within spikelets. These spikelets are arranged in pairs along 2 to 11 (commonly 3 to 7) widely spaced, slender, finger-like branches (racemes) that emerge alternately along the main flower stalk. The racemes are typically 2.5 to 11 centimetres long and often droop or curve. The spikelets themselves are broadly oval, about 3-4 millimetres long, green or purplish, and covered with long, silky hairs, especially along their margins. The plant is hermaphroditic.
Flowering season (South Africa):
Flowers mainly during spring and summer (around September to March), but can flower well into autumn, especially in warmer regions.
Fruits:
The "fruits" are small, elliptic-shaped grains (caryopses), about 2 millimetres long, enclosed within the glumes (bracts) of the spikelet.
Seeds:
Small, reddish-brown, elliptic seeds that are produced in abundance. They are the primary means of dispersal. The seeds can sometimes be infected with an ergot fungus (Claviceps paspali), which makes them sticky and toxic.
Roots:
Develops a deep, thick, fibrous root system from short, creeping underground stems (rhizomes). These rhizomes help the plant form dense clumps and spread vegetatively.
Soil type:
Highly adaptable, growing in a wide range of soil types from sandy loams to heavy clays. It prefers deep, moist, fertile soils, but tolerates poor drainage and can grow in areas with seasonal waterlogging. It is also tolerant of low fertility and moderately acidic to neutral pH levels.
Aspect:
Prefers full sun for optimal growth, but can tolerate some light shade. It is remarkably tolerant of heat and drought once established, thanks to its deep root system.
Edibility:
While sometimes used as a forage grass for livestock, care must be taken as its seed heads can be infected by a toxic ergot fungus. Not edible for human consumption.
Toxicity:
Can be toxic to livestock (especially cattle) if they graze heavily on seed heads infected with the ergot fungus (Claviceps paspali). Ingestion of infected seed heads can cause "dallisgrass staggers," leading to neurological symptoms like trembling, incoordination, and collapse. The plant itself is not inherently toxic without the fungus.
Uses:
Historically and currently used as a perennial pasture and forage grass, particularly in warm temperate and subtropical regions, due to its high production and persistence. It is also used for erosion control and stabilising disturbed areas. However, its invasive tendencies and potential toxicity due to ergot fungus are significant drawbacks.
Ecology:
As an alien invasive plant in South Africa, Paspalum dilatatum can escape cultivation and readily invade disturbed areas, especially those with consistent moisture. It spreads effectively through its abundant seeds, which are dispersed by wind, water, vehicles, and animals, as well as vegetatively via its short, spreading rhizomes. It forms dense, competitive tufts along roadsides, in ditches, stream banks, wetlands, pastures, and neglected areas. While it can provide some forage, its dense growth can outcompete indigenous grasses and herbaceous plants, reducing local biodiversity. Its potential for ergot fungus infection also poses a risk to grazing animals.
Distribution and habitat:
Widely cultivated throughout South Africa as a pasture grass and has become widely naturalised and invasive in all provinces, particularly in areas with higher rainfall and moist conditions. It is very common in the Eastern Cape (frequently found along roadsides, in ditches, moist grasslands, and along waterways around Kenton-on-Sea), KwaZulu-Natal, Mpumalanga, Limpopo, Western Cape, and parts of the Free State and Gauteng. It invades disturbed sites, pastures, wetlands, riverbanks, and other damp, open areas.
Derivation of name:
The genus name Paspalum is derived from the Greek word 'paspalos', referring to a type of millet.
The species epithet dilatatum is Latin, meaning "dilated" or "expanded," possibly referring to the widely spreading branches of its flower head or the somewhat expanded glumes of the spikelets.
The common name "Dallisgrass" is named after A.T. Dallis, who extensively grew it in Georgia, USA, in the late 19th century. "Sticky Heads" refers to the sticky exudate or fungal infection on its seed heads.
Historical aspects:
Paspalum dilatatum was introduced to many parts of the world, including South Africa, primarily as a valuable pasture grass in the late 19th and early 20th centuries due to its high productivity and adaptability to various soil types and moisture conditions. Its hardiness and ability to establish quickly led to its widespread adoption. However, these same traits, combined with its prolific seed production and the spread of its rhizomes, allowed it to escape cultivation and become a widespread and persistent weed and invasive species in many regions globally, including South Africa.
NEMBA status:
While sometimes mentioned in general invasive grass lists, Paspalum dilatatum specifically is not consistently listed as a Category 1b invasive under NEMBA in all publications. However, it is considered a problematic environmental weed that should be managed to prevent its spread in natural and semi-natural areas. For the most up-to-date and authoritative information on its specific NEMBA status, one would need to consult the latest official Alien and Invasive Species Regulations. (Note: Paspalum quadrifarium (Tussock Paspalum) is a Category 1a invasive species in South Africa).
Interesting facts:
This grass is a bit of a trickster! It's sometimes grown by farmers as food for their animals, but if its seeds get a special fungus, they can make livestock wobbly and unwell!
Even though it's called "Dallisgrass," it actually comes all the way from South America, not Dallas, USA!
Its flower heads can sometimes feel a bit sticky to the touch, like they've had a sugar coating! This stickiness is often due to a fungus that can infect the seeds.
This grass is super tough – it can survive in wet ditches, dry roadsides, and even some pretty poor soils, making it a real champion at colonising new places!
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