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Bulbil watsonia (Watsonia meriana)

Bulbil Watsonia is a garden escape and a major environmental weed in Australia, where it forms dense stands in bushland and can exclude other vegetation. It can also crowd out pasture plants and impede farm equipment, although it is of little importance as an agricultural weed.

Key facts

Type: Weed, herb.

Native to: South Africa.

Established in: NSW, VIC, TAS, SA, WA.

Other names: Bugle Lily, Merian's Buglelil, Watsonia, Wild Watsonia.

Best time to act: Look for new leaves in winter and flowering stems from spring, with flowering commencing by late October; treat as stems elongate and the parent corm is exhausted.

Identification

  • It is an erect, clumping perennial herb that can grow to 2.5 m tall.
  • Its tough, fibrous, sword-shaped leaves can reach about 100 cm long and 5 cm wide.
  • In spring and early summer, erect stems carry curved, trumpet-shaped flowers, usually dull orange but sometimes red or pink, about 5–8 cm long.
  • Clusters of egg-shaped bulbils form at the nodes of the flowering stem, replacing the lower flowers; fruit and seeds are generally not produced in Australia.
  • The underground corm is renewed annually and is covered with a fibrous tunic.
  • Look-alike: It can be confused with other Watsonia, including Watsonia meriana var. meriana, but Bulbil Watsonia produces bulbils on the stem.
  • Look-alike: Montbretia has narrower leaves, about 1–2 cm wide, and alternately bent flower stems; African Cornflag has an upper flower lobe much longer than the lower petals, unlike Bulbil Watsonia's six equal flower lobes.

Where it grows

It is widely naturalised in moist-temperate southern and eastern Australia, especially in winter-wet areas such as riverbanks, creeklines and roadside drains, but can also establish on drier sandy sites.

Why it matters

  • It invades woodlands, heathlands, seasonal wetlands and riparian vegetation, forming dense stands that exclude other plants.
  • In south-west Australia it threatens remnant vegetation along the Darling Scarp and threatened plant communities in seasonally inundated clay-based wetlands.
  • It crowds out desirable pasture plants and impoverishes soil; dead top-growth can create fire hazards and the plant can impede farm implements.
  • The plant is suspected of being poisonous to livestock, though animals apparently are unaffected by eating young shoots.

How it spreads

  • It spreads by corms and bulbils, and occasionally by seed; these can be moved by earthmoving equipment, farm implements, vehicles, stock and water.
  • New infestations often originate from dumped garden refuse or bulbils carried in soil and on mowers and slashing equipment.
  • It can also be dispersed in hay, silage and grain.

Control options

  • Use selective control where it occurs among native plants; wiping individual leaves with herbicide can be effective but is time-consuming and may be impractical.
  • Apply registered herbicides at the right stage: as flowering stems elongate and the parent corm is exhausted, around the emergence of the flower spike; check current information with the APVMA.
  • Hand-pull in winter or spring when the ground is soft and wet, removing the corm; remove stems that cannot be destroyed before bulbils disperse.
  • For heavy agricultural infestations, deep cultivation followed by raking up and removing or burning corms is described; grazing can control spread, pigs eat bulbils, and slashing close to the ground before flowering can reduce stem and bulbil formation.

Hygiene and washdown

  • Avoid moving soil or plant material containing corms or bulbils, and clean earthmoving equipment, vehicles, farm implements, mowers and slashing equipment after work in infested areas.
  • Avoid spreading infested hay, silage or grain.
  • Inspect and clean vehicles, plant and footwear before leaving an infested area, paying attention to tyres, radiators, belly plates, tracks and floor mats.
  • Wash down at a designated bay where runoff is contained and can be monitored for seedlings.
  • Record each washdown so the client has evidence of clean entry and exit.

Classification by state

  • Australia (national): No national listing. Managed under state and territory law.
  • Queensland: Not prohibited or restricted. Not listed as prohibited or restricted matter in Queensland. Everyone must also take all reasonable and practical steps to minimise its risks (the general biosecurity obligation).
  • New South Wales: Not a priority weed. Not a state or regional priority weed in NSW. The general biosecurity duty applies: anyone dealing with it must prevent, eliminate or minimise the risk it poses.
  • Victoria: Regionally controlled / restricted weed (varies by region). Where it is regionally controlled, landowners must take all reasonable steps to prevent its growth and spread on their land. Where it is a restricted weed, trade in it (including the plant, its seed or contaminated material) is prohibited.
  • South Australia: Declared plant. Depending on the declaration, it can be an offence to move it on public roads or sell it, and landowners may be required to control it on their land.
  • Western Australia: Permitted, not declared. Listed as a permitted organism in WA, so it can be brought in, but it is not a declared pest.
  • Tasmania: Not declared. Not a declared weed in Tasmania. Other laws may still apply.
  • Northern Territory: Not declared. Not on the NT A to Z weed list, and Weeds Australia does not list it as declared in the NT. Check the NT declared weeds list before moving or planting it.
  • Australian Capital Territory: Not declared. Not declared under the Biosecurity Act 2023 (ACT). A general biosecurity duty still applies.

Legal obligations

Every state and territory places a duty on landholders and people working on land to prevent the spread of invasive species, such as the general biosecurity obligation in Queensland and the general biosecurity duty in New South Wales. Declarations and control requirements differ between states and local government areas, so check the current official list before work starts.

  • New South Wales: Biosecurity Act 2015 (NSW), administered by NSW Department of Primary Industries and Regional Development
  • Victoria: Catchment and Land Protection Act 1994 (Vic), administered by Agriculture Victoria
  • Tasmania: Biosecurity Act 2019 (Tas), administered by Biosecurity Tasmania
  • South Australia: Landscape South Australia Act 2019 (SA), administered by the regional landscape board
  • Western Australia: Biosecurity and Agriculture Management Act 2007 (WA), administered by the WA Department of Primary Industries and Regional Development

Sources