Invasiveness Assessment - Crown Beard (Verbesina encelioides) in Victoria
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Plant invasiveness is determined by evaluating a plant’s biological and ecological characteristics against criteria that encompass establishment requirements, growth rate and competitive ability, methods of reproduction, and dispersal mechanisms.
| Each characteristic, or criterion, is assessed against a list of intensity ratings. Depending upon information found, a rating of Low, Medium Low, Medium High or High is assigned to that criterion. Where no data is available to answer a criterion, a rating of medium (M) is applied. A description of the invasiveness criteria and intensity ratings used in this process can be viewed here. |
The following table provides information on the invasiveness of Crown beard.
A more detailed description of the methodology of the Victorian Weed Risk Assessment (WRA) method can be viewed below:
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Common Name: Crown beard
Scientific name: Verbesina encelioides
| Question | Comments | Rating | Confidence |
| Establishment | |||
| Germination requirements? | Seeds germinate in autumn or early winter (Parsons and Cuthbertson 2001). A study found that maximum germination occurred with seeds from plants of ‘open and sand dune areas’. Germination after rain events were quick, and the presence or absence of light did not influence seed germination (Kaul and Mangal 1987). | MH | MH |
| Establishment requirements? | Grows best in the 800-900 mm annual rainfall zone (Parsons and Cuthbertson 2001) and is adapted to fine medium textured soils. Species is intolerant of shading, requiring access to light to establish (USDA 2007). V. encelioides invades areas predominately of dry climates and in sandy soils of open or disturbed areas (Shluker 1999). | ML | MH |
| How much disturbance is required? | Documented as invading roadsides, stock routes, wasteland, field headlands, near water courses and other disturbed sites (Parsons and Cuthbertson 2001; Richardson et. al. 2006). Also occurs in some woodland communities and valley grassland, these natural ecosystems are relatively intact with minor disturbance (Calflora 2007; Parsons and Cuthbertson 2001). | MH | MH |
| Growth/Competitive | |||
| Life form? | Erect annual herb growing to 150 cm in height (Parsons and Cuthbertson 2001). Life form: Other | L | MH |
| Allelopathic properties? | Root leachate significantly reduces the growth of radish seedlings (Inderjit 1999). Allelopathic effects attribute to the species dominant coverage and success in inhibiting native plant growth (Shluker 1999). | MH | H |
| Tolerates herb pressure? | V. encelioides is extremely toxic not readily eaten by stock except when feed is limited, not a preferred food source (Parsons and Cuthbertson 2001). Plant is poisonous to livestock (Richardson et. al. 2006). | MH | MH |
| Normal growth rate? | ‘The aggressive and dominant growth abilities of the species prevent the growth of less aggressive native plants’ (Shluker 1999). Growth rate maybe similar to the same lifeform. | M | MH |
| Stress tolerance to frost, drought, w/logg, sal. etc? | V. encelioides seed can survive under a wide range of climatic conditions including droughts and high temperatures (Kaul and Mangal 1987). In it native range the plant is found up to 9,000 feet in elevation. Occurs where runoff enhances water supply and where rainfall is 800-900 mm annually (Parsons and Cuthbertson 2001). Also tolerates alkaline soils which are unfavourable to many other species (Kaul and Mangal 1987). | ML | H |
| Reproduction | |||
| Reproductive system | Sexual; V. encelioides demonstrates an efficient ability for both self and cross-pollination (Kaul and Mangal 1987). | ML | H |
| Number of propagules produced? | V. encelioides seeds are numerous; a study showed a single flower head yielded 300-350 seeds (Shluker 1999), and can produce 2-6 capitulum (Walsh and Entwisle 1999). Therefore, most likely to produce between 1,000-2,000 propagules per flowering event. | MH | MH |
| Propagule longevity? | No literature found for propagule longevity. | M | L |
| Reproductive period? | Flowering commences in October or November and continues throughout summer whilst there is sufficient moisture (Harden 2002). Plants die in early autumn, producing viable propagules for only one year (Parsons and Cuthbertson 2001). | L | MH |
| Time to reproductive maturity? | V. encelioides is an annual herb, reaching maturity and producing viable propagules in under a year. Generally the highest level of flowering occurs in the warmer months after significant rainfalls (Shluker 1999). | H | MH |
| Dispersal | |||
| Number of mechanisms? | Spread only by seed, V. encelioides is suited to disperse by wind and animals. Seeds can adhere to wool, fur, clothing, bags and other fibrous materials. May also be spread as an impurity in pasture hay and cereal grain and during road grading (Parsons and Cuthbertson 2001). Seeds are easily dispersed by light winds (Shluker 1999). | MH | MH |
| How far do they disperse? | “Seeds anchored by bristles in wool, fur clothing, bags and other fibrous materials may travel long distances” May also be spread as an impurity in pasture hay and cereal grain and during road grading (Parsons and Cuthbertson 2001). Seeds are easily dispersed by light winds (Shluker 1999). Likely that at least one propagule will disperse greater than one kilometre. | H | MH |
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© The State of Victoria, 1996 - 2009.
This document was last reviewed on 25/09/2009