The initial surge of common yarrow is probably caused by
extensive rhizome sprouting; mineral soil exposure and the
resulting favorable seedbed; less competition from tree,
grass and shrub cover; and nutrient release [28,53].
A burn was conducted each April for at least 24 years on a
rough fescue (Festuca scabrella) grassland in a
quaking aspen parkland in east-central Alberta. Average
frequency and canopy cover for common yarrow were as
follows [3]:
Density and crown area of common yarrow
(per 180,000 in2)following an August wildfire
of moderate severity in a northeastern California range
dominated by bitterbrush (Purshia tridentata)
and various perennial bunchgrasses were as follows [23]:
Productivity values (kg/ha) of common yarrow before and after
a late August fire in western Wyoming quaking aspen communities
are listed below for plots of different burn intensities [9]:
On ponderosa pine and Douglas-fir communities in the Blue Mountains of northeastern Oregon, common yarrow cover
and frequency were higher on sites that had been burned 4 years previously than on thinned,
thinned-and-burned, or control sites. Common yarrow was determined to be
an indicator species for burned sites (P≤0.05). For further information on the effects of thinning and burning
treatments on common yarrow and 48 other species, see the Research Project Summary
of Youngblood and others' [50] study.
For further information on prescribed fire use and common yarrow response to fire, see Fire Case Studies,
Lyon's Research Paper
(Lyon 1966),
Hamilton's Research Paper
(Hamilton 2006b),
and the following Research Project Summaries:
Common yarrow is a perennial forb 11 to 40 inches (30-100 cm) in height with extensive rhizomes. It has few to numerous erect stems. The basal rosette of leaves may remain green throughout the winter [43]. Plants grow in a somewhat scattered fashion and seldom form pure stands in areas larger than 5 square meters [69]. Typical European Achillea millefolium is hexaploid with flat leaves. Native forms are mostly tetraploid, with narrow leaf-segments disposed in various planes so that the leaf is 3-dimensional [33].
McLean [49] reported that in a Douglas-fir (Pseudotsuga menziesii) forest zone in British Columbia, the fibrous roots and rhizomes of yarrow grew mostly in the duff layer or between it and the mineral soil.
The life cycle of common yarrow in grasslands is completed by the onset of the summer drought and fire season in July [6]. Following fire, regeneration is from rapid rhizome spread [72] and wind dispersal of seeds onto burned sites from adjacent unburned areas [41].
Common yarrow occurs in plant communities with a variety of FIRE REGIMES. The range of fire intervals reported for some species that dominate communities where common yarrow occurs are listed below. To learn more about the FIRE REGIMES in these communities, refer to the FEIS summary for that species, under "FIRE ECOLOGY OR ADAPTATIONS."
Community dominant Range of fire interval (yr) interior ponderosa pine 20-42 (Pinus ponderosa var. scopulorum) Rocky Mt. Douglas-fir 10-30 (Pseudotsuga menziesii var. glauca) quaking aspen 7-10 (Populus tremuloides) rough fescue 5-10 (Festuca altaica)Common yarrow's rhizomes and mycorrhizae are usually only slightly damaged by fire [10,38,60], although common yarrow is susceptible to fire-kill and reduction by severe fire [51].
Common yarrow is not highly flammable. Out of 14 species commonly found in boreal forests, common yarrow has the lowest potential ignitability based on chemical characteristics measured on live stem, live leaf and dead leaf tissues. These rankings rely primarily on total ash, silica-free ash and energy content [40]. Ignitability is measured as time to ignition.
Common yarrow varies greatly in forage value, depending on locality and seasonal development. It is generally unpalatable, although domestic livestock and wildlife occasionally consume the flowers. Cattle and horses usually do not graze common yarrow, but bighorn sheep, pronghorn, and deer may use it. They most often graze the flowerheads. common yarrow provides fair forage for domestic sheep and goats [24,43]. The average summer use is 20% for cattle and horses and 40% for domestic sheep and goats [58]. Common yarrow is an important food of 4- to 8-week-old sage grouse chicks [16].
Common yarrow contains volatile oils, alkaloids, and glycosides but is not generally considered a toxic plant because it is so seldom consumed by livestock. Milk from cows consuming common yarrow has a "disagreeable" flavor [64].
Native Americans used tea made from common yarrow to relieve ear-, tooth-, and headaches; as an eyewash; to reduce swelling; and as a tonic or stimulant. common yarrow varies in taste and in potency depending on where it grows and at what stage of growth it is in. The best time to collect yarrow for tea is right before the flowers are produced, using only the new succulent leaves [34]. During the Civil War, common yarrow was widely used to treat wounds and became known as "soldiers' woundwort." An ethanol extract of common yarrow has mosquito- repelling properties [67].
Common yarrow is used for summer and winter bouquets. When cut fresh and kept in water, common yarrow flavors the air with an aromatic spiciness [43,64].
Common yarrow has a long flowering season throughout its range, which varies as follows [19]:
State Earliest Most Frequent Latest Month Month Month --------------------------------------------------- CO May May Jun ID Apr May Jun MT May May Jun UT Apr May Jun WY May Jun Aug
Average dates of different growth stages at different elevations in Utah were recorded as follows [22]:
Elev. Flower buds Flowers Seeds Seeds Plant (ft) evident in bloom ripe disseminated dried --------------------------------------------------------------- 7,150 May 30 Jun 29 Sept 28 Sept 19 Oct 10 7,655 Jun 01 Jul 05 Aug 26 Sept 24 Oct 13 8,450 Jun 06 Jul 10 Sept 04 --- Sept 25 9,000 Jun 18 Jul 15 Sept 08 Sept 29 Oct 01 10,100 Jun 25 Jul 21 Sept 20 Oct 08 Oct 08Average heights (cm) of plants at various dates and altitudes from Ephraim Canyon in Utah were as follows (1925-1934) [22]:
Alt.(ft) May 1 May 15 Jun 1 Jun 15 Jul 1 Jul 15 ----------------------------------------------------- 7,150 4.9 9.1 16.2 26.2 30.8 33.9 7,655 3.9 8.0 12.9 20.0 28.4 31.1 8,450 1.4 4.6 7.7 15.8 24.2 29.3 9,000 -- 0.5 3.5 7.9 19.0 28.3 10,100 -- -- -- 5.1 11.1 19.9Over a 10-year period in Saskatchewan, Canada, flowering dates were recorded for yarrow [18]:
Mean ------------First flowering date----------- Latest date flowering earliest date & yr latest date & yr mean in flower period ------------------ ---------------- ----- -------- ------ May 28/1946 Jun 30/1950 Jun 19 Sept 23 78 daysFire results in fragmentation of common yarrow's rhizomes stimulating regeneration [15]. Cover and frequency of common yarrow generally increase 1 to 2 years after fire but not with any consistent pattern [4,13,14,32,40,56,71]. After initially increasing in cover, common yarrow may decrease to unburned levels as early as 3 years after fire [17,37,65,75]. Production doubled within 3 to 4 years postfire near Missoula, Montana [6] and other ponderosa pine/mountain grassland ecosystems [32,69]. In another study of fire effects in ponderosa pine, common yarrow increased by 0.37 stem/m in 6 years, a negligible amount [55].
Common yarrow ground layer on the Stanislaus National Forest, 15 months after the 2013 Rim Fire.Common yarrow is responsive to season of burning. Late spring burning usually reduces common yarrow [4,12,66].
Rhizomatous herb, rhizome in soil
Initial-offsite colonizer (off-site, initial community)
FIRE REGIMES: Find fire regime information for the plant communities in which this species may occur by entering the species name in the FEIS home page under "Find FIRE REGIMES".
Common yarrow regenerates from fragments of rhizomes and from colonization through short-distance (1-2 m) wind dispersal of seeds [15,47,61]. In disturbed soils, fragmented rhizomes regenerate shoots which can emerge from soil depths as great as 12 inches (30 cm). In undisturbed soil the rhizomes remain attached to the parent plant, forming new plants at the rhizome apices [15].
The fruit is a small achenes weighing about 0.17 mg. They are produced in large numbers. Several thousand achenes may be produced per flowering stem. The viability of freshly shed seeds exceeds 90%. Common yarrow seed showed 41% germination after 9 years in dry storage [15].
