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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.|
|Germination requirements?||Requires natural seasonal disturbances, such as rainfall/temperature/day length for germination.|
Preference for wet, sandy habitats. (Goldblatt, ’92).
Germinates in autumn. (Blood, ‘01).
|Establishment requirements?||Requires specific requirement (full sun / moisture) to establish.|
Invades grass- and heathland, woodlands, and riparian habitats. (Weber, ’03).
Preference for wet, sandy habitats. (Goldblatt, ’92).
Full sun required. (Blood, ‘01).
|How much disturbance is required?||Establishes in highly disturbed natural ecosystems.|
Grows along roadsides, on vacant land and disturbed bushland (Botanic Gardens Trust, ’99-’07; Harden, ‘93).
Invades heathland and heathy woodland, lowland, grassland and grassy woodland and dry sclerophyll forest and woodland communities. (Carr et al. ‘92)
Perrenial (Goldblatt, ’92).
Cormour geophyte. (Carr et al. ‘92).
[NB. It is noteworthy that Sparaxis spp. readily form intrageneric hybrids (e.g. Blood, ’01). Some authors do not distinguish between Sparaxis spp., putative hybrids, or varieties; but treat them as an aggregate (e.g. Hitchmough, ’89 and Hussey, et al. ‘97). Although this assessment only looks at S. bulbifera, it may be needful to consider other Sparaxis spp. known to be in Australia that may have differing weedy potentials that may hybridise with S. bulbifera.]
|Allelopathic properties?||Not described as having Allelopathic properties.|
|Tolerates herb pressure?||Consumed, but not preferred by herbivores AND growth encouraged by grazing.|
Plants rarely eaten by animals, encouraged by light to moderate grazing. (Blood, ‘01).
|Normal growth rate?||Rapid growth rate that will exceed most other similar species.|
Establish quickly (Richardson, et al. ’06).
Sparaxis sp. will crowd out small native plants. (http://www.treesforlife.org.au) (external link).
|Stress tolerance to frost, drought, w/logg, sal. etc?||Resistant to drought, frost, and waterlogging. Not recorded as being susceptible to salinity.|
Tolerates temperatures to -5°C, full sun, dry and wet conditions, various soils including sand and clay. Prefers moist conditions particularly drainage lines, roadside drains seasonal wetlands: (Blood, ‘01). Therefore assumed tolerant of some water logging. (Ibid. ‘01) Drought and frost resistant (Bodkin, ‘86)
|Reproductive system||Both sexual AND vegetative reproduction.|
Reproduce by seed, corms and leaf bulbs. (Muyt, ‘01).
May self-pollinate (Goldblatt et al. ’00).
Insect pollinated whilst being visited by hopliine beetles (Lepithrix ornatella), short-proboscid flies (Mesomyia sp.), and pollen-collecting bees (Ibid.) for nectar.
Reproduction vegetative (corms & bulbs), seeds in West Australia and New Zealand. (Blood, ‘01)
|Number of propagules produced?||50 – 1,000 propagules per plant.|
Goldblatt (’92) refers to a “remarkably constant” seed number, i.e. 8 – 10 seeds per locule, with 24 – 30 per floral capsule.
Six flowers per plant (Hitchmough ’89).
“Extremely prolific producer of corms and cormlets.” (Blood, ‘01).
- Assumed 50-1,000 propagules (or less), as plants only ~ 30 cm. (Van der Spuy, ‘71)
|Propagule longevity?||Not recorded in literature reviewed.|
|Reproductive period?||Mature plant produces viable propagules for three - ten years.|
Corms assumed to produce bulbs and seeds for > three years. (PFF ‘02).
Forming large swards along roadsides and in other areas. In badly infested areas the task may well be daunting, as the infestations can be very dense. (http://www.treesforlife.org.au) (external link).
Perennial herb with above ground parts that die back each year to an underground corm. (Blood, ‘01)
|Time to reproductive maturity?||Produces propagules one – two years after germination.|
Flowering plants within two years of seed germination (Hitchmough, ’89).
This species often flowers in its second year from seed. --- Corms assumed to produce bulbs and seeds for > three years. (PFF ‘02)
|Number of mechanisms?||Propagules spread by various means, including wind, water, soil movement; NOT by attachment or faunal food source.|
Soil movement carries vegetative propagules (Esler, ’88).
Seed and bulbils dispersed by water, wind, slashing, in garden refuse, and soil movements (Muyt, ’01).
Corms dispersed in garden refuse, and soil movement. (Muyt, ’01).
Corms and cormlets…are easily transported and spread by slashing equipment and erosion. Cormlets easily transported in water (runoff) and soil. (Blood, ‘01).
Seeds are completely spherical and perfectly Smooth (Goldblatt, ’92) reducing the likelihood of seed attachment being a significant mode of transport.
Seeds without structures aiding ready dispersal include S. bulbifera according to Esler (’88).
|How far do they disperse?||Very likely that at least one propagule will disperse greater than one kilometre.|
Small infestations can be spread for several kilometres by road making equipment. (Blood, ‘01).
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