Ambrosia confertiflora DC.

Title: Ambrosia confertiflora DC.

Scientific Name:

Ambrosia confertiflora DC.

Common Names:

burr ragweed

Image via GBIF

Habitat:

Dry plains of temperate regions, variety of soils. Occurring as a weed in run-down pastures, orchards, roadsides, wastelands and other disturbed areas. Native of southern United States and Mexico. Confined to small colonies in south-east Queensland and Central Western Slopes and North Western Plains of New South Wales (Parsons & Cuthbertson 2001).

Distribution:

Image via GBIF

Invasiveness Assessment

ESTABLISHMENT

1. Germination requirements? Germinates in autumn (Parsons & Cuthbertson 2001). Requires natural seasonal conditions.

2. Establishment requirements? Prefers dryplains of temperate regions and is a weed of wastelands (Parsons & Cuthbertson 2001). Limited growth in shade.

3. How much disturbance is required? Occurs in ‘run-down pastures, orchards, roadsides, wastelands and other disturbed areas’ (Parsons & Cuthbertson 2001). Established in highly disturbed natural ecosystems.

GROWTH / COMPETITIVE

4. Life form? Perennial herbaceous plants (Parsons & Cuthbertson 2001). Life form – other.

5. Allelopathic properties? A. confertiflora not documented to have allelopathic properties (Parsons & Cuthbertson).

6. Tolerates herb pressure? A. confertiflora not known to be eaten by animals and insects.

7. Normal growth rate? Seedlings grow at moderate rate during winter with growth rate increasing in spring (Parsons & Cuthbertson 2001). No indication that plant growth rate would equal competitive species of same life form. Therefore score as medium.

8. Stress tolerance to frost, drought, w/logg, sal. etc? ‘When dry periods occur in summer, aerial growth dies back and redevelops from the perennial roots in autumn’ Drought tolerant. Can be found in flood plains but no mention of ability to withstand waterlogging (Parsons & Cuthbertson 2001). Due to locations found, assume weed has some tolerance to salinity.

REPRODUCTION

9. Reproductive system? Reproduces sexually and vegetatively (Parsons & Cuthbertson 2001).

10. Number of propagules produced? “All types (of ragweed) are prolific seeders … average about 3,000 seeds per year’ (Parsons & Cuthbertson 2001).

11. Propagule longevity? Annual ragweed propagule longevity is up to 40 years (Schmoll, Reigner & Harrison 2004). In contrast, giant ragweed is only viable for 6 weeks (Parsons & Cuthbertson 2001). No information on A. confertiflora. Due to variation within genus, scored as medium.

12. Reproductive period? Not specified. Form large colonies and plants known to live up to 10 years (Parsons & Cuthbertson 2001). Therefore score as medium high.

13. Time to reproductive maturity? A. confertiflora reaches maturity in approximately 9 months (Parsons & Cuthbertson 2001).

DISPERSAL

14. Number of mechanisms?“Known to be dispersed by clinging to sheep, furred animals, bags, clothing, water, contaminated gravel and soil (Parsons & Cuthbertson 2001).

15. How far do they disperse? Spreads ‘readily over long distances’. Hull provides buoyancy (Parsons & Cuthbertson 2001). Assume likely that some of the propagules will disperse greater than 1 km.

Impact Assessment

RECREATION

1. Restrict human access? Grows from 75 to 200 cm. The burrs associated with burr ragweed and dermatogenic properties have the potential to impede individual access (Parsons & Cuthbertson 2001).

2. Reduce tourism? Most species are ‘so ordinary in appearance that they are rarely noticed despite their abundance’. All species are noted for their allergens and are a major contributor to hay fever in US, with some places advertising as ‘ragweed free’ (Parsons & Cuthbertson 2001). Potential to have major impact on tourism in autumn months when pollen counts is high.

3. Injurious to people? ‘Most important hay-fever producing plant in North America’. Also associated with asthma and dermatogenic properties. Burr ragweed ‘burrs’ cause discomfort throughout the year with three species having a high pollen count from late summer through to autumn being a major component in hayfever and asthma (Parsons & Cuthbertson 2001).

4. Damage to cultural sites? Not known to cause structural damage. Little or negligible effect on aesthetics.

ABIOTIC

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

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

7. Increase soil erosion? In dry periods over summer and in autumn, aerial growth dies back. Plants have ‘creeping runner-like roots’ and form large colonies (Parsons & Cuthbertson 2001). Unlikely that the species would contribute to large-scale soil erosion.

8. Reduce biomass? Plant grows up to 200 cm and forms large colonies. Often occurs in wasteland where little vegetation exists (Parsons & Cuthbertson 2001). Likely that biomass would slightly increase.

9. Change fire regime? Herbaceous plant (Parsons & Cuthbertson 2001) so assume that it would have small or negligible effect on fire risk.

COMMUNITY HABITAT

10(a) Impact on composition of high value EVC? EVC=Plains Grassy Woodland (E), CMA=Wimmera, Bioreg.=Wimmera, CLIMATE=VH. Weed doesn’t occur in healthy, well-established ecosystems. Occurs mostly in open, disturbed areas where less than 3 strata are present (Parsons & Cuthbertson 2001). Very little displacement of any indigenous species.

10(b) Impact on medium value EVC? EVC=Hills Herb-rich Woodland (D), CMA=NorthCentral, Bioreg=Goldfields, CLIMATE=VH. Weed doesn’t occur in healthy, well-established ecosystems. Occurs mostly in open, disturbed areas where less than 3 strata are present (Parsons & Cuthbertson 2001). Very little displacement of any indigenous species.

10(c) Impact on low value EVC? EVC=Coastal Tussock Grassland (LC), CMA=West Gippsland, Bioreg.=Gippsland Plain, CLIMATE=L. Weed doesn’t occur in healthy, well-established ecosystems. Occurs mostly in open, disturbed areas where less than 3 strata are present (Parsons & Cuthbertson 2001). Very little displacement of any indigenous species.

11. Impact on structure? Weed doesn’t occur in healthy, well-established ecosystems. Occurs mostly in open, disturbed areas where less than 3 strata are present (Parsons & Cuthbertson 2001). Usually only affecting one of the strata.

12. Effect on threatened flora? No information available.

FAUNA

13. Effect on threatened fauna? No information available.

14. Effect on non-threatened fauna? Tends to grow in ruderal sites so assume that there is no reduction in habitat/food/shelter for non threatened fauna spp. (Parsons & Cuthbertson 2001).

15. Benefits fauna? No documented evidence that A. confertiflora benefits fauna.

16. Injurious to fauna? Hooked spines and burrs attach to sheep and furred animals but no documented impact on health or well being of animals (Parsons & Cuthbertson 2001).

PEST ANIMAL

17. Food source to pests? No documented evidence that A. confertiflora is a food source to pests (Parsons & Cuthbertson 2001).

18. Provides harbor? No documented evidence that A. confertiflora provides harbour for pest spp.

AGRICULTURE

19. Impact yield? ‘Is an extremely competitive plant, readily suppressing pasture species…also a problem in orchards, competing for nutrients’ (Parsons & Cuthbertson 2001). Minor impact on quantity of produce.

20. Impact quality? Burr ragweed contaminates wool with hooked spines (Parsons & Cuthbertson 2001). Likely that would have greater than 5% impact on quality of produce.

21. Affect land values? No information on whether or not the weed affects land value. Numerous studies on effect of annual ragweed and giant ragweed on cropping systems but no references made to burr ragweed and land values. Score medium.

22. Change land use? See above. Weed can be controlled by herbicides in pasture (Parsons & Cuthbertson 2001). Assume little or no change in priority of land use.

23. Increase harvest costs? Weed can be controlled by herbicides in pasture (Parsons & Cuthbertson 2001). Assume little or no change in priority of land use.

24. Disease host/vector? None evident.

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

The entry of this assessment was made possible through the generous support of Nature's Weeding Centre.

Feedback

Do you have additional information about this plant that will improve the quality of the assessment? If so, we would value your contribution. Enter your feedback in the comment box below.

Attachments:

https___inaturalist-open-data.s3.amazonaws.com_photos_225141124_original.jpeg
Screenshot 2023-02-18 180600.jpg

referenced by (1)

wra825: Common Name - B (via burr ragweed)

Article: wra8605 (permalink)
Categories: :wra:a, :wra:inv1, :wra:invmh, :wra:inv2, :wra:invml, :wra:inv3, :wra:inv4, :wra:invl, :wra:inv5, :wra:inv6, :wra:invh, :wra:inv7, :wra:invm, :wra:inv8, :wra:inv9, :wra:inv10, :wra:inv11, :wra:inv12, :wra:inv13, :wra:inv14, :wra:inv15, :wra:imp1, :wra:impml, :wra:imp2, :wra:imph, :wra:imp3, :wra:impmh, :wra:imp4, :wra:impl, :wra:imp5, :wra:imp6, :wra:imp7, :wra:imp8, :wra:imp9, :wra:imp10a, :wra:imp10b, :wra:imp10c, :wra:imp11, :wra:imp12, :wra:imp13, :wra:imp14, :wra:imp15, :wra:imp16, :wra:imp17, :wra:imp18, :wra:imp19, :wra:imp20, :wra:imp21, :wra:impm, :wra:imp22, :wra:imp23, :wra:imp24
Date: 18 February 2023; 6:09:33 PM AEDT

Author Name: David Low
Author ID: adminDavid