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Invasiveness Assessment - Hemlock (Conium maculatum) in Victoria (Nox)

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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 Hemlock.

A more detailed description of the methodology of the Victorian Weed Risk Assessment (WRA) method can be viewed below:

Victorian Weed Risk Assessment (WRA) method (PDF - 630 KB)
Victorian Weed Risk Assessment (WRA) method (DOC - 1 MB)
To view the information PDF requires the use of a PDF reader. This can be installed for free from the Adobe website (external link).

Common Name: Hemlock
Scientific name: Conium maculatum

Question
Comments
Reference
Rating
Establishment
Germination requirements?Seeds mostly germinate in autumn, but sometimes in spring.
P & C (1992)
MH
Establishment requirements?Occurs in ‘shady’ habitats.
Robbins et al (1951)
P & C (1992)
MH
How much disturbance is required?Occurs in minor disturbed natural ecosystems, e.g. grassland, grassy woodland, riparian vegetation, warm temperate rainforest.
Carr et al (1992)
MH
Growth/Competitive
Life form?Erect annual or biennial herb.

Other.
P & C (1992)
L
Allelopathic properties?None described.
L
Tolerates herb pressure?When green, it is rarely eaten by cattle and sheep, probably because of its offensive odour.
P & C (1992)
MH
Normal growth rate?Can preclude most other vegetation.

Is capable of rapid establishment after autumn rains.
P & C (1992)
H
Stress tolerance to frost, drought, w/logg, sal. etc?Tolerance to water logging (occurs on riverbeds), assumably also frost (occurs in southern Tasmania and Canada).
Rutledge & Gupta (1996)
Webb et al (1998)
P & C (1992)
ML
Reproduction
Reproductive systemReproducing by seed.
P & C (1992)
ML/L
Number of propagules produced?(Estimated using pictures in Kleinschmidt & Johnson (1977) & US Department of Agriculture (1976). 30 inflorescence x 10 umbels/inflorescence x 10 florets/umbel x 1 seed/floret = 3,000 seeds per plant.
H
Propagule longevity?Seeds are believed to be short-lived in the soil.
P & C (1992)
L
Reproductive period?Forms dense infestations. See pic. P & C (1992) p. 168
P & C (1992)
H
Time to reproductive maturity?Some plants produce flowering stems in the first spring.
P & C (1992)
H
Dispersal
Number of mechanisms?Machinery, vehicles, agricultural produce, mud and clothing.

Also water, wind, gravel and soil. Annuals (e.g. stock & dogs).
P & C (1992)
Blood (nd)
MH
How far do they disperse?As occurs near waterways, some seeds likely will disperse > 200 m especially in floodwaters. Most more likely to disperse < 200 m.
See Kleinschmidt & Johnson (1977)
ML


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