Pacific Island Ecosystems at Risk (PIER)


Achillea millefolium


RISK ASSESSMENT RESULTS: High risk, score: 19


Australian/New Zealand Weed Risk Assessment adapted for Hawai‘i.
Information on Risk Assessments
Original risk assessment

Achillea millefolium L. Family - Asteraceae. Common Names(s) - Common yarrow, milfoil, bloodwort carpenter's weed. Synonym(s) - A. lanulosa Nutt.; A. borealis Bong.

Answer

Score

1.01

Is the species highly domesticated?

y=-3, n=0

n

0

1.02

Has the species become naturalized where grown?

y=1, n=-1

1.03

Does the species have weedy races?

y=-1, n=-1

2.01

Species suited to tropical or subtropical climate(s) (0-low; 1-intermediate; 2-high) – If island is primarily wet habitat, then substitute “wet tropical” for “tropical or subtropical”

See Append 2

0

2.02

Quality of climate match data (0-low; 1-intermediate; 2-high) see appendix 2

1

2.03

Broad climate suitability (environmental versatility)

y=1, n=0

y

1

2.04

Native or naturalized in regions with tropical or subtropical climates

y=1, n=0

y

1

2.05

Does the species have a history of repeated introductions outside its natural range?

y=-2, ?=-1, n=0

y

3.01

Naturalized beyond native range y = 1*multiplier (see Append 2), n= question 2.05

y

1

3.02

Garden/amenity/disturbance weed y = 1*multiplier (see Append 2)

n=0

y

1

3.03

Agricultural/forestry/horticultural weed y = 2*multiplier (see Append 2)

n=0

y

2

3.04

Environmental weed y = 2*multiplier (see Append 2)

n=0

3.05

Congeneric weed y = 1*multiplier (see Append 2)

n=0

y

1

4.01

Produces spines, thorns or burrs

y=1, n=0

n

0

4.02

Allelopathic

y=1, n=0

n

0

4.03

Parasitic

y=1, n=0

n

0

4.04

Unpalatable to grazing animals

y=1, n=-1

n

-1

4.05

Toxic to animals

y=1, n=0

n

0

4.06

Host for recognized pests and pathogens

y=1, n=0

y

1

4.07

Causes allergies or is otherwise toxic to humans

y=1, n=0

4.08

Creates a fire hazard in natural ecosystems

y=1, n=0

n

0

4.09

Is a shade tolerant plant at some stage of its life cycle

y=1, n=0

y

1

4.10

Tolerates a wide range of soil conditions (or limestone conditions if not a volcanic island)

y=1, n=0

y

1

4.11

Climbing or smothering growth habit

y=1, n=0

n

0

4.12

Forms dense thickets

y=1, n=0

y

1

5.01

Aquatic

y=5, n=0

n

0

5.02

Grass

y=1, n=0

n

0

5.03

Nitrogen fixing woody plant

y=1, n=0

n

0

5.04

Geophyte (herbaceous with underground storage organs -- bulbs, corms, or tubers)

y=1, n=0

y

1

6.01

Evidence of substantial reproductive failure in native habitat

y=1, n=0

n

0

6.02

Produces viable seed.

y=1, n=-1

y

1

6.03

Hybridizes naturally

y=1, n=-1

y

1

6.04

Self-compatible or apomictic

y=1, n=-1

n

-1

6.05

Requires specialist pollinators

y=-1, n=0

n

0

6.06

Reproduction by vegetative fragmentation

y=1, n=-1

y

1

6.07

Minimum generative time (years) 1 year = 1, 2 or 3 years = 0, 4+ years = -1

See left

1

1

7.01

Propagules likely to be dispersed unintentionally (plants growing in heavily trafficked areas)

y=1, n=-1

y

1

7.02

Propagules dispersed intentionally by people

y=1, n=-1

y

1

7.03

Propagules likely to disperse as a produce contaminant

y=1, n=-1

y

1

7.04

Propagules adapted to wind dispersal

y=1, n=-1

y

1

7.05

Propagules water dispersed

y=1, n=-1

n

-1

7.06

Propagules bird dispersed

y=1, n=-1

n

-1

7.07

Propagules dispersed by other animals (externally)

y=1, n=-1

n

-1

7.08

Propagules survive passage through the gut

y=1, n=-1

y

1

8.01

Prolific seed production (>1000/m2)

y=1, n=-1

y

1

8.02

Evidence that a persistent propagule bank is formed (>1 yr)

y=1, n=-1

y

1

8.03

Well controlled by herbicides

y=-1, n=1

8.04

Tolerates, or benefits from, mutilation, cultivation, or fire

y=1, n=-1

y

1

8.05

Effective natural enemies present locally (e.g. introduced biocontrol agents)

y=-1, n=1

Total score:

19

Supporting data:

Notes

Source

1.01

(1)Although wild yarrow is a troublesome weed in fields and gardens, horticulturists have created, selected and hybridized many outstanding cultivars which are beautiful flowering perennials...Even the horticultural selections of yarrow are vigorous and strong growers, adaptable to a wide variety of soils and growing conditions, and likely to spread.

(1)http://www.floridata.com/ref/A/achi_mil.cfm [Accessed 24 Feb 2009]

1.02

1.03

2.01

(1)Common yarrow is a cosmopolitan weed originally native to Europe and western Asia. Today it grows in temperate regions worldwide. (2)Data on the distribution of A. millefolium was used to develop a CLIMEX model of its distribution worldwide and in Australia under current and changing climatic conditions. The models indicate that cool, temperate and Mediterranean climates are suitable for this species, while deserts and tropics are unsuitable.

(1)http://www.floridata.com/ref/A/achi_mil.cfm [Accessed 24 Feb 2009] (2)Johnston, F. M. 2005. Exotic plants in the Australian Alps including a case study of the ecology of Achillea millefolium, in Kosciuszko National Park. Griffith University. Gold Coast, Australia. PhD. Dissertation.

2.02

(1)in Hawaii, naturalized from 1200 to 3000 m on the island of Hawaii. [naturalized at higher elevations, lower elevation limit marginally subtropical]

(1)Wagner, W. L., D. R. Herbst and S. H. Sohmer. 1999. Manual of the Flowering Plants of Hawaii. University of Hawaii and Bishop Museum Press. Honolulu.

2.03

(1)Hardiness: USDA Zones 3 - 9. Many of the cultivars are listed as useful only in zones 4-8. Flower colors often fade and stems tend to be weaker when temperatures are above 80ºF (26.7ºC). (2)Hardiness: Zones 3-10 (3)Achillea millefolium has a wide tolerance to environmental conditions and is adaptable to a broad range of soil types and climates

(1)http://www.floridata.com/ref/A/achi_mil.cfm [Accessed 24 Feb 2009] (2)Gardner, J.A. and H. S. Dougherty. 2005. Herbs in Bloom: A Guide to Growing Herbs as Ornamental Plants. Timber Press. Portland, OR. (3)Bourdot, G. W.1984. Regeneration of yarrow (Achillea millefolium L.) rhizome fragments of different length from various depths in the soil. Weed Research 24, 421–429.

2.04

(1)in Hawaii, naturalized from 1200 to 3000 m on the island of Hawaii. [naturalized at higher elevations, lower elevation limits marginally subtropical]

(1)Wagner, W. L., D. R. Herbst and S. H. Sohmer. 1999. Manual of the Flowering Plants of Hawaii. University of Hawaii and Bishop Museum Press. Honolulu.

2.05

(1)Cultivated in many countries, including Australia.

(1)Johnston, F. M. 2005. Exotic plants in the Australian Alps including a case study of the ecology of Achillea millefolium, in Kosciuszko National Park. Griffith University. Gold Coast, Australia. PhD. Dissertation.

3.01

(1)in Hawaii, naturalized from 1200 to 3000 m on the island of Hawaii. (2)Achillea millefolium L. is a perennial rhizomatous herb native to Europe and Asia that was initially introduced into Australia for its ornamental and herbal qualities. Little is known about this species as a weed in Australia, but in New Zealand it has become a major problem in some arable crops grown in Canterbury and on the Otago high plains (Bourdot, 1984; Field & Jayaweera, 1985).

(1)Wagner, W. L., D. R. Herbst and S. H. Sohmer. 1999. Manual of the Flowering Plants of Hawaii. University of Hawaii and Bishop Museum Press. Honolulu. (2)Sanecki, G. M., K. Ll Sanecki, G. T. Wright, F. M. Johnston. 2003, The control of Achillea millefolium in the Snowy Mountains of Australia. Weed Research Volume 43, Issue 5: 357-361

3.02

(1)In the U.S. it occurs in disturbed areas, road shoulders, meadows and fields from Texas to Florida and north to southern Canada. In Europe, yarrow is a ubiquitous weed in hedgerows, pastures and fields, and seldom allowed near respectable gardens. (2)yarrow can at times invade and compete with other plants, especially in gardens and cropland. Generally the plant's presence indicates poor soil, overgrazing, or land abuse and disturbance. (3)Yarrow can be an obnoxious weed, but is found only sparingly in my garden. (4)Yarrow or Milfoil (Achillea Millefolium L.), although readily eaten by sheep, is inclined to overrun grass land on poor soils, and must therefore be included here as a weed.

(1)http://www.floridata.com/ref/A/achi_mil.cfm [Accessed 24 Feb 2009] (2)Eastman, J. and A. Hansen. 2003. The Book of Field and Roadside: Open-country Weeds, Trees, and Wildflowers of Eastern North America. Stackpole Books. Mechanicsburg, PA. (3)Heiser, C. B. 2003. Weeds in My Garden: Observations on Some Misunderstood Plants. Timber Press. Portland, OR. (4)Long, H. C. 2008. Common Weeds of the Farm & Garden. Read Books. Alcester, UK. (5)Johnston, F. M. 2005. Exotic plants in the Australian Alps including a case study of the ecology of Achillea millefolium, in Kosciuszko National Park. Griffith University. Gold Coast, Australia. PhD. Dissertation.

3.03

(1)Dairy cattle that ingest yarrow are reported to produce off-flavoured milk. (2)in New Zealand it has become a major problem in some arable crops grown in Canterbury and on the Otago high plains

(1)Royer, F. and Richard Dickinson. 1999. Weeds of the Northern U.S. and Canada: A Guide for Identification. University of Alberta. Edmonton, Canada. (2)Bourdot, G. W.1984. Regeneration of yarrow (Achillea millefolium L.) rhizome fragments of different length from various depths in the soil. Weed Research 24, 421–429.

3.04

(1)In the Snowy Mountains, A. millefolium is an environmental weed which primarily occurs along roadways and fire trails, at spoil sites, around buildings and historic sites from where it is able to invade adjacent native vegetation communities...Achillea millefolium poses a serious threat to the vegetation communities of the high altitude areas for a number of reasons. It has a wide tolerance to environmental conditions and once established, if allowed to spread unchecked, has been observed to form a monoculture, inhibiting growth of all other plant species...Although the current infestations of this species are generally confined to disturbed areas, isolated plants have been observed in adjacent natural vegetation [primarily a weed of disturbed sites. Answer Yes to 3.02]

(1)Sanecki, G. M., K. Ll Sanecki, G. T. Wright, F. M. Johnston. 2003, The control of Achillea millefolium in the Snowy Mountains of Australia. Weed Research Volume 43, Issue 5: 357-361

3.05

(1)Achillea borealis, A. lanulosa, A. micrantha, A. nobilis, A. ptarmica and A. santolina listed as weeds (2)Achillea ageratum, Achillea alpina, Achillea asplenifolia, Achillea biebersteinii, Achillea borealis, Achillea cartilaginea, Achillea collina, Achillea conyzoides, Achillea cretica, Achillea crithmifolia, Achillea decolorans, Achillea distans, Achillea filipendulina, Achillea fragrantissima, Achillea grandifolia, Achillea lanulosa, Achillea ligustica, Achillea micrantha, Achillea nobilis, Achillea ochroleuca, Achillea pannonica, Achillea ptarmica, Achillea salicifolia, Achillea santolina, Achillea setacea, Achillea sibirica, Achillea spp., Achillea stricta, Achillea tomentosa [congeneric weeds]

(1)Holm, L. G., J. V. Pancho, J. P. Herberger and D. L. Plucknett. 1991. A Geographical Atlas of World Weeds. Krieger Publishing Company. Malabar, FL. (2)http://www.hear.org/gcw/scientificnames/scinamea.htm [Accessed 26 Feb 2009]

4.01

(1)No evidence

(1)Wagner, W. L., D. R. Herbst and S. H. Sohmer. 1999. Manual of the Flowering Plants of Hawaii. University of Hawaii and Bishop Museum Press. Honolulu.

4.02

(1)In a glasshouse competition experiment between A. millefolium and the dominant native snowgrass Poa fawcettiae, the weed produced four times as much biomass as the native grass at the end of the 12 week experiment…Root interaction from the weed on the grass appeared to be the primary source of competition. [no evidence of allelopathy]

(1)Johnston, F. M. 2005. Exotic plants in the Australian Alps including a case study of the ecology of Achillea millefolium, in Kosciuszko National Park. Griffith University. Gold Coast, Australia. PhD. Dissertation.

4.03

(1)No evidence

(1)Wagner, W. L., D. R. Herbst and S. H. Sohmer. 1999. Manual of the Flowering Plants of Hawaii. University of Hawaii and Bishop Museum Press. Honolulu.

4.04

(1)Forage Value: poor to fair for cattle and fair to good for sheep; usually grazed only when green; heads may be eaten by pronghorn, deer and sheep.

(1)Stubbendieck, J. L., S. L. Hatch, L. M. Landholt, Kelly L. Rhodes Hays. 2003. North American Wildland Plants: A Field Guide. U of Nebraska Press. Lincoln, NE.

4.05

(1)Not generally considered to be poisonous, but may contain toxic alkaloids and glycosides.

(1)Stubbendieck, J. L., S. L. Hatch, L. M. Landholt, Kelly L. Rhodes Hays. 2003. North American Wildland Plants: A Field Guide. U of Nebraska Press. Lincoln, NE.

4.06

(1)Yarrow is an alternate host for chrysanthemum stunt virus.

(1)Royer, F. and Richard Dickinson. 1999. Weeds of the Northern U.S. and Canada: A Guide for Identification. University of Alberta. Edmonton, Canada.

4.07

(1)Some people may develop an allergic reaction from contact with the foliage or sap of yarrow. Prolonged use is said to make the skin sensitive to light. Floridata does not advocate the use of any herb or medicine without your doctor's knowledge and supervision. In the garden, common yarrow can be invasive and out compete other less aggressive plants. [certain people may be susceptible]

(1)http://www.floridata.com/ref/A/achi_mil.cfm [Accessed 24 Feb 2009]

4.08

(1)Fire-Retardant Ground Covers: includes Achillea millefolium

(1)MacKenzie, D. S. 2006. Timber Press Pocket Guide to Ground Covers. Timber Press. Portland, OR.

4.09

(1)Light: Full sun. (2)Favoring open land (high or low) and abundant sunlight, it also tolerates shade

(1)http://www.floridata.com/ref/A/achi_mil.cfm [Accessed 24 Feb 2009] (2)Eastman, J. and A. Hansen. 2003. The Book of Field and Roadside: Open-country Weeds, Trees, and Wildflowers of Eastern North America. Stackpole Books. Mechanicsburg, PA.

4.10

(1)can persist on many soil types, including sandy and unfertile sites.

(1)Eastman, J. and A. Hansen. 2003. The Book of Field and Roadside: Open-country Weeds, Trees, and Wildflowers of Eastern North America. Stackpole Books. Mechanicsburg, PA.

4.11

(1)Rhizomatous perennial herbs

(1)Wagner, W. L., D. R. Herbst and S. H. Sohmer. 1999. Manual of the Flowering Plants of Hawaii. University of Hawaii and Bishop Museum Press. Honolulu.

4.12

(1)It has a wide tolerance to environmental conditions and once established, if allowed to spread unchecked, has been observed to form a monoculture, inhibiting growth of all other plant species.

(1)Johnston F. M. and C. M. Pickering. 2001. Yarrow, Achillea millefolium L.: a weed threat to the flora of the Australian Alps. The Victorian Naturalist 118(1): 21–24..

5.01

(1)Terrestrial

(1)Wagner, W. L., D. R. Herbst and S. H. Sohmer. 1999. Manual of the Flowering Plants of Hawaii. University of Hawaii and Bishop Museum Press. Honolulu.

5.02

(1)Asteraceae

(1)Wagner, W. L., D. R. Herbst and S. H. Sohmer. 1999. Manual of the Flowering Plants of Hawaii. University of Hawaii and Bishop Museum Press. Honolulu.

5.03

(1)Asteraceae

(1)Wagner, W. L., D. R. Herbst and S. H. Sohmer. 1999. Manual of the Flowering Plants of Hawaii. University of Hawaii and Bishop Museum Press. Honolulu.

5.04

(1)It has many survival features also found in Australian native alpine plants such as drought resistance, underground storage organ, frost resistance and a herbaceous perennial life form.

(1)Johnston F. M. and C. M. Pickering. 2001. Yarrow, Achillea millefolium L.: a weed threat to the flora of the Australian Alps. The Victorian Naturalist 118(1): 21–24..

6.01

(1)No evidence

(1)Johnston, F. M. 2005. Exotic plants in the Australian Alps including a case study of the ecology of Achillea millefolium, in Kosciuszko National Park. Griffith University. Gold Coast, Australia. PhD. Dissertation.

6.02

(1)reproduces from seeds and rhizomes

(1)Stubbendieck, J. L., S. L. Hatch, L. M. Landholt, Kelly L. Rhodes Hays. 2003. North American Wildland Plants: A Field Guide. U of Nebraska Press. Lincoln, NE.

6.03

(1)The entire species consists of many hybrid variations of both native and alien forms. (2)There are hundreds of cultivars that have been created by crossing and backcrossing among a dozen or so species of Achillea.

(1)Eastman, J. and A. Hansen. 2003. The Book of Field and Roadside: Open-country Weeds, Trees, and Wildflowers of Eastern North America. Stackpole Books. Mechanicsburg, PA. (2)http://www.floridata.com/ref/A/achi_mil.cfm [Accessed 24 Feb 2009]

6.04

(1)self-incompatible

(1)Warwick, S. I. and L. Black. 1982. The biology of Canadian weeds 52. Achillea millefolium L. Canadian Journal of Plant Science 62: 163-182.

6.05

(1)A range of insects have been found to act as pollinators for A. millefolium in Canada including species from Diptera, Coleoptera, Hymenoptera, Lepidoptera and Hemiptera

(1)Warwick, S. I. and L. Black. 1982. The biology of Canadian weeds 52. Achillea millefolium L. Canadian Journal of Plant Science 62: 163-182.

6.06

(1)It can be invasive for it increases rapidly by creeping roots, establishing colonies of attractive, ferny foliage 8 in. (20.3 cm( long and flat-topped flower clusters that bloom on straight stems into the fall. (2)An extensively branched rhizome allows the plant to form large colonies.

(1)Gardner, J.A. and H. S. Dougherty. 2005. Herbs in Bloom: A Guide to Growing Herbs as Ornamental Plants. Timber Press. Portland, OR. (2)Royer, F. and Richard Dickinson. 1999. Weeds of the Northern U.S. and Canada: A Guide for Identification. University of Alberta. Edmonton, Canada.

6.07

(1)Can flower within 1 year

(1)Johnston, F. M. 2005. Exotic plants in the Australian Alps including a case study of the ecology of Achillea millefolium, in Kosciuszko National Park. Griffith University. Gold Coast, Australia. PhD. Dissertation.

7.01

(1)During the 1990s, populations seem to have increased dramatically, possibly as a result of the use of gravel from weed contaminated dumps (Johnston & Pickering, 2001) or contaminated hay used for rehabilitation works (GT Wright, pers. comm.).

(1)Sanecki, G. M., K. Ll Sanecki, G. T. Wright, F. M. Johnston. 2003, The control of Achillea millefolium in the Snowy Mountains of Australia. Weed Research Volume 43, Issue 5: 357-361

7.02

(1)Cultivated as a medicinal plant in Central Europe, England and Australia (New South Wales). (2)Ornamental

(1)Hanelt, P., R. Büttner, R. Mansfeld and R. Kilian. 2001. Mansfeld's Encyclopedia of Agricultural and Horticultural Crops. Springer. Berlin, Germany. (2)Gardner, J.A. and H. S. Dougherty. 2005. Herbs in Bloom: A Guide to Growing Herbs as Ornamental Plants. Timber Press. Portland, OR.

7.03

(1)During the 1990s, populations seem to have increased dramatically, possibly as a result of the use of gravel from weed contaminated dumps (Johnston & Pickering, 2001) or contaminated hay used for rehabilitation works (GT Wright, pers. comm.).

(1)Sanecki, G. M., K. Ll Sanecki, G. T. Wright, F. M. Johnston. 2003, The control of Achillea millefolium in the Snowy Mountains of Australia. Weed Research Volume 43, Issue 5: 357-361

7.04

(1)Dispersal of the seed is primarily by wind with the small seed (~0.158 mg) having limited aerodynamic efficiency with the average dispersal distance of 2 to 3 m from the parent.

(1)Bourdot, G. W., J. G. H. White and R. J. Field. 1979, Seasonality of growth and development in yarrow. Proceedings of the New Zealand Weed and Pest Control Conference 32: 49-54.

7.05

(1)No evidence

(1)Johnston, F. M. 2005. Exotic plants in the Australian Alps including a case study of the ecology of Achillea millefolium, in Kosciuszko National Park. Griffith University. Gold Coast, Australia. PhD. Dissertation.

7.06

(1)Dispersal of the seed is primarily by wind with the small seed (~0.158 mg) having limited aerodynamic efficiency with the average dispersal distance of 2 to 3 m from the parent. [not fleshy fruited]

(1)Bourdot, G. W., J. G. H. White and R. J. Field. 1979, Seasonality of growth and development in yarrow. Proceedings of the New Zealand Weed and Pest Control Conference 32: 49-54.

7.07

(1)Seeds (achenes) are described as oblong 1.5-2.0 mm long with thick wing-margins, without a pappus and are grey-white. [no means of external attachment]

(1)Johnston, F. M. 2005. Exotic plants in the Australian Alps including a case study of the ecology of Achillea millefolium, in Kosciuszko National Park. Griffith University. Gold Coast, Australia. PhD. Dissertation.

7.08

(1)Viable seed dispersed in animal feces

(1)Johnston, F. M. 2005. Exotic plants in the Australian Alps including a case study of the ecology of Achillea millefolium, in Kosciuszko National Park. Griffith University. Gold Coast, Australia. PhD. Dissertation.

8.01

(1)Each plant is capable of producing 4000 seeds. (2)The seed ecology of A. millefolium was examined including estimating the potential maximum seed production (51400 seeds/m2)...

(1)Royer, F. and Richard Dickinson. 1999. Weeds of the Northern U.S. and Canada: A Guide for Identification. University of Alberta. Edmonton, Canada. (2)Johnston, F. M. 2005. Exotic plants in the Australian Alps including a case study of the ecology of Achillea millefolium, in Kosciuszko National Park. Griffith University. Gold Coast, Australia. PhD. Dissertation.

8.02

(1)Research has shown that after 9 years, 41% of all seeds still viable. (2)There was 60% viability of seed remaining after three years dry storage and 16% viability of seed remaining after three years of burial in the field.

(1)Royer, F. and Richard Dickinson. 1999. Weeds of the Northern U.S. and Canada: A Guide for Identification. University of Alberta. Edmonton, Canada. (2)Johnston, F. M. 2005. Exotic plants in the Australian Alps including a case study of the ecology of Achillea millefolium, in Kosciuszko National Park. Griffith University. Gold Coast, Australia. PhD. Dissertation.

8.03

(1)The response of Achillea millefolium L. to herbicides was measured to determine the effectiveness of the current recommendations and to test alternative herbicides. Five plots at each of the three replicate sites were selected and randomly treated with one of the four herbicides: dicamba/2,4-D, glyphosate, metsulfuron-methyl and triclopyr/picloram. After 12 months, the recommended treatment, dicamba/2,4-D, did not cause a significant reduction in aerial biomass compared with untreated controls and the number of flowering stems was significantly increased in treated plots. Metsulfuron-methyl and triclopyr/picloram caused a significant reduction in A. millefolium aerial biomass but did not affect the number of flowering stems. Glyphosate produced a significant reduction in aerial biomass and was less effective. These results suggest that the current recommendation for A. millefolium might be improved. Sitespecific effects such as aspect may also influence the effectiveness of herbicides on this species...In the absence of a proven alternative method, chemicals currently appear to be the only viable short-term option for control. However, adopting an alternative to dicamba/2,4-D needs special consideration, as many chemical products currently available may have a more lethal effect on A. millefolium while having negative effects on native species, especially products designed for the control of woody weeds and/or those having some residual effect. [apparently able to be controlled by herbicides in certain situations, but effectiveness of some is limited]

(1)Sanecki, G. M., K. Ll Sanecki, G. T. Wright, F. M. Johnston. 2003, The control of Achillea millefolium in the Snowy Mountains of Australia. Weed Research Volume 43, Issue 5: 357-361

8.04

(1)The regenerative response of the rhizomes of Achillea millefolium L. to fragmentation and burial was studied in field experiments on three different soils. The percentage of buds producing shoots (estimated from surviving rhizome fragments) from 4 cm (1·6 nodes), 8 cm (3·8 nodes) and 16 cm (6·7 nodes) rhizome fragments was 63, 44 and 32 respectively averaged over all soils and depths of 5, 10 and 15 cm. The depth at which 50% of the fragments failed to produce an emerged shoot (LD50 depth) was 9·3, 12·4 and 17·9 cm for 4-, 8- and 16-cm fragments respectively averaged over all soils. No fragments survived on the soil surface. The time of emergence of the first shoots was delayed and the rate of emergence and ultimate shoot population reduced with increasing depth of burial. Dry-matter production by aerial shoots and new rhizomes decreased linearly with depth of burial of the rhizome fragments. Soil type had no effect on the regeneration of the fragments. The significance of the results for the control of A. millefolium is discussed. (2)However, yarrow becomes a problem when a paddock is cultivated and a crop sown. The rhizome system allows the yarrow to survive cultivation, so the re-establishing plants cause major competition problems with crop plants. Likewise, yarrow is commonly found in turf. Once established in a lawn, yarrow is very tolerant of frequent mowing. However, it is unable to form seed-heads under constant mowing, so instead relies on vegetative spread by rhizomes to produce new plants.

(1)Bourdot, G. W.,1984. Regeneration of yarrow (Achillea millefolium L.) rhizome fragments of different length from various depths in the soil. Weed Research Volume 24, Issue 6: 421-429. (2)http://weeds.massey.ac.nz/weeds.asp?pid=46 [Accessed 26 Feb 2009]

8.05

Unknown


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