Title: Iva axillaris Pursh
Scientific Names:
Dry often alkaline places in plains, valleys and foothills, often on disturbed sites.
1. Germination requirements? Seeds are thought to germinate in spring, about the same time that shoots develop from the root system.” Requires natural seasonal disturbance to germinate (Parsons & Cuthbertson 2001).
2. Establishment requirements? It prefers alkaline, poorly drained soils. In Australia, it occurs in a few areas on cultivated land and pastures. Requires open areas with access to sunlight and moisture (Parsons & Cuthbertson 2001).
3. How much disturbance is required? In California, U.S., the plant occurs on, “… alkaline plains, edges of salt marshes, cultivated fields, pastures, roadsides [and] waste places.” Establishes in highly disturbed ecosystems. (CDFA)
4. Life form? Tree Perennial herb, reproducing from creeping roots and seed. Geophyte (Parsons & Cuthbertson 2001).
5. Allelopathic properties? “Poverty weed is allelopathic; extracts from the leaves reduce germination and root and shoot development of wheat, and root extracts inhibit growth of several grasses and legumes.” Allelopathic properties seriously affecting some plants (Parsons & Cuthbertson 2001).
6. Tolerates herb pressure? “… it is seldom grazed because of its strong smell and taste.” Not eaten. (Parsons & Cuthbertson 2001)
7. Normal growth rate? Iva axillaris competes strongly with cereal crops. No records exist of its competitiveness with other weedy perennials. It develops new growth in spring and matures and flowers in summer. Its growth rate may exceed other species of the same life form. (Parsons & Cuthbertson 2001)
8. Stress tolerance to frost, drought, w/logg, sal. etc? “Food reserves in the deep roots allow new growth to develop in drought years.” The plant occurs on saline soils and the deep root system may ensure it survive periods of frost. “… poverty weed… is a natural component of many grassland communities that experience periodic fire.” Able to survive fire. (Parsons & Cuthbertson 2001, CDFA)
9. Reproductive system? Reproduces from creeping roots and seed. (Parsons & Cuthbertson 2001)
10. Number of propagules produced? About 6 or 7 seeds produced in each flower head, of which there are many on each stem. Stems numerous. Possibly more than 2,000 seeds per plant. (Parsons & Cuthbertson 2001)
11. Propagule longevity? Little is known of the viability or longevity of seed. In the U.S., “… studies have shown some seed may be viable after two years of freshwater storage.”
12. Reproductive period? “Poverty weed is a long-lived perennial.” (Parsons & Cuthbertson 2001)
13. Time to reproductive maturity? Seeds germinate in spring; plants mature in summer producing flowers and seed. Mature in under one year. (Parsons & Cuthbertson 2001)
14.Number of mechanisms? The seed is not equipped with a pappus, so is not adapted to wind dispersal. It can contaminate agricultural produce, seed, machinery and can survive c. 8 months submerged in water. Within a property dispersal can occur through the distribution of root fragments on cultivation equipment. (Parsons & Cuthbertson 2001; CDFA)
15.How far do they disperse? Much of the spread of this plant is due the creeping roots. In Canada viable seed is seldom produced. This may also be the case in Australia, where the current infestation has not spread. The main method of spread may be on contaminated agricultural machinery; thus, dispersal would be limited to less than 1 kilometre. (Parsons & Cuthbertson 2001)
1. Restrict human access? A perennial herb commonly 20 cm to 30 cm high. It would not restrict human access.(Parsons & Cuthbertson 2001)
2. Reduce tourism? It produces dense aerial growth and its presence would be obvious. The leaves produce an unpleasant aromatic odour when crushed. This aspect of the plant may limit some recreational activities. (CDFA)
3. Injurious to people? “it causes contact dermatitis in some people while its abundant pollen has exacerbated hay-fever problems.” (Parsons & Cuthbertson 2001)
4. Damage to cultural sites? As a strong competitor with dense aerial growth. It would create a negative visual effect seriously affecting the aesthetics of a site. (Parsons & Cuthbertson 2001)
5. Impact flow? Terrestrial species. (Parsons & Cuthbertson 2001)
6.Impact water quality? Terrestrial species.(Parsons & Cuthbertson 2001)
7. Increase soil erosion? An extensive perennial root system to 2.5 metres deep consisting of both vertical and horizontal roots. Colonises cultivated land or overgrazed pastures. Aerial growth dies in autumn leaving the potential for surface soil erosion. (Parsons & Cuthbertson 2001)
8. Reduce biomass? Can replace biomass.
9. Change fire regime? Aerial growth dies in autumn. Little matter remains to establish or support fire.
10(a) Impact on composition of high value EVC? EVC=Plains grassy woodland (E); CMA=Wimmera; Bioreg=Wimmera; VH CLIMATE potential.
In the U.S., it occurs mostly in grassland (rangeland) situations. It sometimes forms large clonal colonies on disturbed sites where it is difficult to eradicate. Major displacement of grasses/forbs in open situation. Effect in woodland situation may be limited.
10(b) Impact on medium value EVC? Distribution limited to northwest of Victoria. Limited data on EVC available. It does not appear to affect any medium value EVCs.
10(c) Impact on low value EVC? As in 10(b) above.
11. Impact on structure? “With its extensive root system and dense aerial growth, poverty weed competes strongly with other plants. Almost no crop is produced in heavily infested areas. Poverty weed is allelopathic.” Occurs in open disturbed or neglected areas. Likely to have a serious impact on the lower stratum in open situations. (Parsons & Cuthbertson 2001)
12. Effect on threatened flora? No effects documented.
13. Effect on threatened fauna? No effects documented.
14. Effect on non-threatened fauna? It, “competes strongly with other plants…and large areas of infested pasture in western Canada have little or no grazing value.” As it is not grazed by livestock, its presence would lead to a reduction in available food for native species. (Parsons & Cuthbertson 2001)
15. Benefits fauna? No known benefits.
16. Injurious to fauna? In Canada “there have been reports that poverty weed is a selenium accumulator and may be toxic to livestock when ingested. However, this is very rare due to the unpalatable nature of the plant.” Not considered toxic.
17. Food source to pests? No known as a food source to pests.
18. Provides harbor? Low growth habit of plant would not provide harbour.
19. Impact yield? “It is highly competitive when established in agricultural fields and may significantly reduce crop yields.” “Almost no crop is produced in heavily infested areas.” Major impact on production. (Parsons & Cuthbertson 2001; CDFA)
20. Impact quality? “Its seeds are a common contaminant of legume and grass seed crops in some areas.” Impact not documented, though contaminated crop may be difficult to sell due to the competitive nature of the weed. (Parsons & Cuthbertson 2001)
21. Affect land values? Its impact on yield in both grazing and cropping situations, and the difficulty in controlling the plant, suggest land value may be seriously affected.
22. Change land use? “…cultivation and repeated workings over 3 years in Canada did not eliminate the weed…herbicides offering the only effective treatment. Large areas of grazing land in Canada have little or no grazing value.” Potential for significant agricultural loss. (Parsons & Cuthbertson 2001)
23. Increase harvest costs? No known effect on harvest costs.
24. Disease host/vector? None evident.
Do you have additional information about this plant that will improve the quality of the assessment? If so, we would value your contribution.
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Date: 28 January 2023; 2:09:31 PM AEDT
Author Name: David Low
Author ID: adminDavid
