Conium maculatum L.

Title: Conium maculatum L.

Scientific Name:

Conium maculatum L.

Common Name:

hemlock

Source & more images (via ALA)

Habitat: Humid and subhumid temperate regions where it is usually found in shaded sites on moist fertile loam soils (Parsons and Cuthbertson 1992). It is a weed of waste places, creek banks and low-lying pastures (Parsons and Cuthbertson 1992). Hemlock invades lowland grassland and grassy woodland, riparian vegetation, and warm temperate rainforest (Carr et al 1992).

Distribution:

Original source via CABI

Weed Assessment

ESTABLISHMENT

1. Germination requirements? Seeds mostly germinate in autumn, but sometimes in spring. (Parsons & Cuthbertson, 1992)

2. Establishment requirements? Occurs in ‘shady’ habitats. (Robbins et al., 1951; Parsons & Cuthbertson, 1992)

3. 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)

GROWTH / COMPETITIVE

4. Life form? Erect annual or biennial herb. (Parsons & Cuthbertson, 1992)

5. Allelopathic properties? None described.

6. Tolerates herb pressure? When green, it is rarely eaten by cattle and sheep, probably because of its offensive odour. (Parsons & Cuthbertson, 1992)

7. Normal growth rate? Can preclude most other vegetation. Is capable of rapid establishment after autumn rains. (Parsons & Cuthbertson, 1992)

8. 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). (Webb et al., 1998; Rutledge & Gupta, 1996; Parsons & Cuthbertson, 1992)

REPRODUCTION

9. Reproductive system? Reproducing by seed. (Parsons & Cuthbertson, 1992)

10. 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

11. Propagule longevity? Seeds are believed to be short-lived in the soil. (Parsons & Cuthbertson, 1992)

12. Reproductive period? Forms dense infestations. (See pic. Parsons & Cuthbertson, 1992 p. 168)

13. Time to reproductive maturity? Some plants produce flowering stems in the first spring. (Parsons & Cuthbertson, 1992)

DISPERSAL

14. Number of mechanisms? Machinery, vehicles, agricultural produce, mud and clothing. Also water, wind, gravel and soil. Annuals (e.g. stock & dogs). (Blood, n.d; Parsons & Cuthbertson, 1992)

15. 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. (Kleinschmidt & Johnson 1977)

Impact Assessment

RECREATION

1. Restrict human access? An erect herb to 3 metres high, similar in form to Foeniculum vulgare. Hemlock is capable of rapid establishment on disturbed sites or where little vegetation exists. Once firmly established, hemlock precludes most other vegetation. The stems emit an offensive odour when damaged. This plant would be a significant nuisance to humans, but unlikely to create a serious physical barrier. (Parsons & Cuthbertson, 2001)

2. Reduce tourism? In Victoria, it grows mainly on moist neglected areas, usually near streams. Dense infestations may inhibit some recreational activities. (Parsons & Cuthbertson, 2001)

3. Injurious to people? “…all plant parts are toxic to humans.” (Muyt, 2001)

4. Damage to cultural sites? Growth to 3 metres; in dense stands its presence would create a negative visual impact seriously affecting the aesthetics of a cultural site. (Parsons & Cuthbertson, 2001)

ABIOTIC

5. Impact flow? Terrestrial species. (Parsons & Cuthbertson, 2001)

6. Impact water quality? Terrestrial species. (Parsons & Cuthbertson, 2001)

7. Increase soil erosion? Roots comprise a large taproot, sometimes branched, with numerous lateral roots. Dense infestations may provide some soil binding. However, it is an annual/biennial plant, can preclude most other vegetation in dense infestations, and favours moist areas such as stream banks. Possibility of moderate large scale soil movement in riparian situations. (Parsons & Cuthbertson, 2001)

8. Reduce biomass? Dense growth mostly on disturbed sites or where there is little vegetation. Biomass likely to increase. (Parsons & Cuthbertson, 2001)

9. Change fire regime? Dense patches would produce a large amount of litter in late summer when the plant dies. May increase the frequency of fire risk. (Parsons & Cuthbertson, 2001)

COMMUNITY HABITAT

10(a) Impact on composition of high value EVC: EVC=Riparian scrub (E); CMA=West Gippsland; Bioreg=Gippsland Plain; VH CLIMATE potential. “…growing mainly on moist neglected areas, usually near streams. Once firmly established…hemlock precludes most other vegetation.” Major displacment of dominant species within the lower layers. (Parsons & Cuthbertson, 2001)

10(b) medium value EVC: EVC=Heathy woodland (D); CMA=Port Phillip; Bioreg=Central Victorian Uplands; VH CLIMATE potential. “Once firmly established…hemlock precludes most other vegetation.” Major displacment of dominant species within the lower layers. (Parsons & Cuthbertson, 2001)

10(c) low value EVC: EVC=Heathy woodland (LC); CMA=West Gippsland; Bioreg=Gippsland Plain; VH CLIMATE potential. “Once firmly established…hemlock precludes most other vegetation.” Major displacment of dominant species within the lower layers. (Parsons & Cuthbertson, 2001)

11. Impact on structure? Dense infestations can develop in disturbed areas and preclude most other vegetation. “Poison hemlock may act as a pioneer species quickly colonising disturbed sites and displacing natives during early succession seres.” Would have a major negative impact on the 20–60% of the floral strata. (Parsons & Cuthbertson, 2001; Pitcher, 1989)

12. Effect on threatened flora?

FAUNA

13. Effect on threatened fauna?

14. Effect on non-threatened fauna? “The presence of C. maculatum degrades habitat quality and could indicate a management problem on an ecological reserve.” The plant is poisonous; would reduce the habitat of native fauna. (Parsons & Cuthbertson, 2001; Pitcher, 1989)

15. Benefits fauna? No benefits

16. Injurious to fauna? C. maculatum is poisonous to livestock, but livestock rarely eat the plant due to its offensive odour. Some risk to fauna. (Parsons & Cuthbertson, 2001; Pitcher, 1989)

PEST ANIMAL

17. Food source to pests? The plant is poisonous. Unlikely to be a food source to pest animals. (Parsons & Cuthbertson, 2001)

18. Provides harbor? Dense infestations may provide limited harbor to minor pest species such as rodents.

AGRICULTURE

19. Impact yield? Because the plant is poisonous, it can reduce yield either through the non-availability of pasture or directly through stock deaths. “Losses of cattle have been recorded in all southern States of Australia.” It can reduce milk yields. (Parsons & Cuthbertson, 2001)

20. Impact quality? “It also taints milk.”

21. Affect land values? Because of the poisonous nature of the plant, it may have a negative impact on the value of agricultural land. (Parsons & Cuthbertson, 2001)

22. Change land use? “Seeds are believed to be short-lived in the soil.” Infestations can be controlled readily with cultivation or by chemicals. Plant residues remain poisonous; infested areas would have to be quarantined until all plant matter is removed. Temporary change to land use. (Parsons & Cuthbertson, 2001; Pitcher, 1989)

23. Increase harvest cost? Not a weed of cropping. No evidence of impact on harvesting.

24. Disease host/vector? “In the British Isles, hemlock acts as a host for the carrot fly, Psila rosea, when growing close to carrot fields, and is also host for the celery yellow spot virus.” (Parsons & Cuthbertson, 2001)

Feedback

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Assessment ratings originally made by the Victorian Department of Primary Industries.

The entry of this assessment was made possible through the generous support of The Weed's Network.

Attachments:

hemlock_plant.jpg
COMA2.png
conium via ala.JPG
distribution_map (18).png

referenced by (2)

wra1029: Common Name - P (via poison hemlock)wra1002: Common Name - H (via hemlock)

Article: wra8 (permalink)
Categories: :wra:c, :wra:inv1, :wra:invmh, :wra:inv2, :wra:inv3, :wra:inv4, :wra:invl, :wra:inv5, :wra:inv6, :wra:inv7, :wra:inv8, :wra:invml, :wra:inv9, :wra:inv10, :wra:invh, :wra:inv11, :wra:inv12, :wra:inv13, :wra:inv14, :wra:inv15, :wra:imp1, :wra:impml, :wra:imp2, :wra:imp3, :wra:imph, :wra:imp4, :wra:impmh, :wra:imp5, :wra:impl, :wra:imp6, :wra:imp7, :wra:imp8, :wra:imp9, :wra:imp10a, :wra:imp10b, :wra:imp10c, :wra:imp11, :wra:imp12, :wra:impm, :wra:imp13, :wra:imp14, :wra:imp15, :wra:imp16, :wra:imp17, :wra:imp18, :wra:imp19, :wra:imp20, :wra:imp21, :wra:imp22, :wra:imp23, :wra:imp24
Date: 13 May 2009; 3:40:35 PM AEST

Author Name: David Low
Author ID: adminDavid