Quick Facts

Quick facts

• Originally from Southern Africa and Madagascar, Watsonia species are erect perennial herbs forming large clumps with strap-like leaves, producing taller flowering-spikes from 0.5 to 2 m high with many flowers.
• Plants produce leaves and flowering stems annually, and these die back to ground level re-growing each year.
• Of the 70 Watsonia species under half of these are cultivated in gardens in Australia, with seven species and several varieties as known weeds.
• It is mainly an environmental weed of moist sites flourishing in riparian and well-drained sites alike.
• Can be a problem in remnant native vegetation and road reserves, forms dense stands excluding other vegetation.
• The production of underground cormels has enabled species spread vegetatively.
• Corms and cormels can remain dormant in the soil for a considerable period.
• Can be controlled by physical and chemical means with efforts required over numerous years to eradicate infestations.
• For information on Bulbil Watsonia see: Weeds Australia (2021) https://profiles.ala.org.au/opus/weeds-australia/profile/Watsonia%20meriana%20var.%20bulbillifera 

What Does It Look Like?

What is it?

Watsonias (Watsonia spp.) are erect large perennial herbs forming clumps (similar to gladiolus), with leaves and flowering stems produced annually (dying back to ground level over summer and autumn, and re-growing each growing season). Clumps of strap-like leaves are produced before larger taller slender flowering stems to 2 m high are produced bearing showy flowers variously white to pink, orange, or red. Watsonia leaves are 20 to 80 cm long and 2 to 5 cm wide and are shaped like the blade of a sword. They are tough, fibrous, lack hairs, and have a prominent central midrib and numerous smaller parallel veins, and often arise fan-like from the top of the normally underground or emerging corm (swollen underground plant stems). Corms give rise to further clusters of smaller underground corms (known as cormels) that are a means of vegetative spread (propagation). 

Flowers are produced on tall flowering stems that are sometimes branched or with side branches. Flowers are curved and trumpet-shaped, with 6 petals (perianth segments) forming a tube then opening into a wide funnel. Flowers are mostly 5 to 8 cm long and 3 to 4 cm in diameter and are arranged singly, 2.5 to 4 cm apart, in opposite rows along the upper part of the flowering-stem and on side branches. 

The fruit is an ovoid (egg shaped), woody capsule, 2 to 4 cm long, with three cavities; opening from the apex into 3 valves. Seeds oblong, winged. However, fruits are often not produced on plants in Australia (Faithfull 2000). 

For further information and photographs on cultivated Watsonia species see: Pacific Bulb Society (2018) https://www.pacificbulbsociety.org/pbswiki/index.php/Watsonia 

For a list of known weedy Watsonia species, see APC (2021) https://biodiversity.org.au/nsl/services/search/taxonomy?product=APC&tree.id=51209179&name=watsonia&inc._scientific=&inc.scientific=on&inc._cultivar=&max=100&display=apc&search=true . 

For further information and assistance with identification of Watsonia contact the herbarium in your state or territory.

Flower colour

White, Orange, Pink, Red

Growth form (weed type/habit)

Herb

Where it currently grows? Preferred habitat

Species of Watsonia are typically found in moist situations in temperate and subtropical regions often on heavy soils. It usually starts as a weed of roadsides and neglected areas, then readily invades native vegetation particularly grasslands, grassy woodland and swampy areas (Faithfull 2000).

Are there similar species?

No native plants can be easily mistaken for Watsonia, except perhaps the smaller and pale-flowered native Diplarrena. Many Watsonia species and their hybrids are cultivated in gardens in Australia, and some of these may be expected to naturalise. 

Several species of garden gladiolus are escaped weeds in southern Australia. Gladiolus differ from Watsonia in having three stigma-branches at the end of the style rather than six (Faithfull 2000). 

When the plants are vegetative they can easily be confused with other weedy Iridaceae weedy plants.  Foe a positive identification of Watsonia and the species and varieties flowers are required.

Why Is It A Weed?

What are its impacts?

Watsonia was included in the list of 71 species that were nominated by state and territory governments for assessment as Weeds of National Significance (WONS). Following an assessment process, Watsonia was not included as one of the 20 WONS. However, it remains a weed of potential national significance.

Agriculture: Some species of Watsonia are suspected of being poisonous to livestock, but animals do not graze large plants and are apparently unaffected by consumption of young shoots. Selective grazing by stock results in desirable pasture species being replaced by Bulbil Watsonia with a consequent decrease in stocking capacity. Wild Watsonia impoverishes soil and crowds out desirable pasture plants. It can cause serious loss of production but rarely persists in well managed paddocks and cultivated areas and is of little importance as an agricultural weed. Only a weed in unimproved pastures especially those in high rainfall and waterlogged areas only encroaches into other pastures that have been un-grazed for extended periods

Native ecosystems: It is more significant as an environmental weed, and can be an aggressive weed of native vegetation invading threatened native vegetation especially urban and peri-urban areas, in swamps, and along creek lines, forming dense colonies that exclude other plants (Faithfull 2000; APCCSA 2001). In native woodlands and along watercourses Watsonia can form continuous clonal stands that exclude other ground-layer species. Corms and cormels generally survive fire and prolific flowering and cormel or bulbil set can follow summer fire.

Urban areas: Also invades roadsides, wasteland and unimproved pasture in high rainfall and waterlogged areas.

How does it spread?

The cormels of Watsonia can be widely scattered by moving water, in soil on vehicles and nachinary,  and can be dispersed in hay, silage and grain. The bulbils and underground cormels can also be efficiently spread by contaminated soil and equipment. Most new infestations probably originate from dumped garden refuse Species that set seed in Australia are readily dispersed by seed in the same way as the bulbils and cormels (Faithfull 2000).

What is its history in Australia?

Watsonia has been cultivated in Australia for more than 150 years, with records of plants being offered for sale in nursery catalogues in Victoria in the 1850s. Six species of Watsonia have been recorded as naturalised in victoria and 6 in conservation reserves and state forests in Western Australia including Kings Park, Perth. They are all believed to be garden escapes. Because they are of garden origin it is often difficult to determine the exact species. 

The most weedy species, Bulbil Watsonia (W. meriana var. bulbillifera),  is of uncertain origin. It probably arose spontaneously as a localised variation of the typical W. meriana in South Africa and was then taken into cultivation. It has a number of undesirable horticultural features and may best be classified as a variety that evolved naturally in an environment subject to human disturbance rather than a cultivar. 

Fertile plants producing seed are rare in Australia and some authors consider bulbil Watsonia to be sterile (Faithfull 2000; Groves et al. 2005). 

Watsonia species weedy in Australia as listed by the Australian Plant Census (APC 2021) are: 

Watsonia aletroides (Burm.f.) Ker Gawl. 

Watsonia meriana var. bulbillifera (J.W.Mathews & L.Bolus) D.A.Cooke 

Watsonia borbonica (Pourr.) Goldblatt

Watsonia knysnana L.Bolus

Watsonia marginata (L.f.) Ker Gawl.

Watsonia meriana var. bulbillifera (J.W.Mathews & L.Bolus) D.A.Cooke

Watsonia meriana (L.) Mill. var. meriana

Watsonia versfeldii J.W.Mathews & L.Bolus 

How To Manage It?

Best practice management

Watsonia can be controlled by physical means, and with herbicides. If controlling a populations along a water courses, start at the top of the water course as prologues (seeds, bulbils, corms and cormels) spread along water courses in the direction of water flow establishing on the side waterways. 

Chemical control: Germinated corms and cormels can be controlled with herbicides. The herbicide glyphosate is generally recommended for the control of Watsonia. With correct use of herbicides at the right time of the year a 90% success rate can be expected (Day 1992; EWAN undated). Herbicides can be applied foliar spray or in sensitive native vegetation via spongy tongs (or similar tool) that coats both sides of the leaves with herbicide. See Herbiguide (2021) for strategies targeting the control of Watsonia species. 

Please see the Australian Pesticides and Veterinary Medicines Authority for chemical information http://www.apvma.gov.au

Non-chemical control: Manual removal can be a very effective way of controlling Watsonia when it occurs in isolated patches in bushland or other areas. The timing of hand removal work is particularly important in wetland situations as the soil needs to be wet enough to allow easy removal of the large clumps of corms and attached cormels, but not so wet that trampling and soil compaction are a problem. Observation of Watsonia growing on sandier soils indicate that the corms lie deeper and hand removal can be more difficult than on the heavier soils. The removal of flowering stems from all plants in a given population prevents bulbils or seed production and therefore recruitment of new Watsonia plants into a given area. Small infestations can be grubbed but corms  must be removed and burnt otherwise they will re shoot forming new plants.

Grazing provides effective control on emerging and new growth only at the start of the growing season. Cultivation to 100 mm provides good control if done after the old corm is exhausted and before the new corms form or before the flower stem emerges. Dig up plants to determine their stage. A follow up cultivation is also needed. Mowing and slashing are ineffective unless repeated very regularly.  In pastures, establishment of suitable pasture species will prevent re-infestation from Watsonia species.

Does it have a biological control agent?

NO

When does it grow? (lifecycle/growth calendar)

Corms or cormels (underground stems) of Watsonia start to grow in late autumn and foliage is produced during the winter. Flowering stems are produced in spring and flowering occurs mainly in November and December. Plants that develop from cormels do not flower in the first year but may flower in their second or third years. Plants become dormant in late summer and autumn when the foliage and stems die off. The plant reproduces by replacement and multiplication of the underground corms and by cormels (Faithfull 2000).

Where Is It Found?

Which states and territories is it found?

NSW, QLD, SA, TAS, VIC, WA

What areas within states and territories is it found?

Species of Watsonia are weeds in the wetter south coast and south-west of Western Australia, in the Mount Lofty Ranges of South Australia, throughout much of Victoria at low altitudes, in southern and eastern New South Wales, the south east of Queensland, and in eastern Tasmania (APCCSA 2001; Faithfull 2000; AVH 2021).

Where does it originate?

Watsonia species are native to southern Africa and Madagascar. 

National And State Weed Listings

Is it a Weed of National Significance (WONS)?

NO

Where is it a declared weed?

SA 

Government weed strategies and lists – Weeds Australia

Is it on the National Alert List for Environmental Weeds?

NO

Government weed strategies and lists – Weeds Australia

Is it on the Agricultural Sleeper List?

NO

Government weed strategies and lists – Weeds Australia

Names And Taxonomy

Main scientific name

Watsonia spp.

Other scientific names (synonyms)?

Does it have other known common name(s)?

Watsonia, Bulbil Watsonia, Wild Watsonia, Bugle Lily.