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meadow hawkweed

Pilosella caespitosa

Description 9

More info for the terms: cover, density, tussock

Botanical description: This description covers characteristics that may be relevant to fire ecology and is not meant for identification. Keys for identification are available (e.g., [31,63,83,92,98,112,120]).
Meadow hawkweed is a rhizomatous [49,108] and/or stoloniferous perennial herb [49,108,115] that exudes a milky sap when damaged. Leaves, stems, and stolons are conspicuously hairy [108]. A flora describes meadow hawkweed stolons as long and leafy [49]. Plants have a basal rosette and 10 to 30 flower stems that are 10 to 36 inches (25-91 cm) in height. A stem produces 5 to 30 yellow flowers arranged in a flat-topped cluster [77]. Meadow hawkweed seeds are small achenes that are 1.5 to 2 mm long [108] and weigh approximately 0.09 mg [87]. Seeds have a tawny tuft of bristles at one end [117].

Meadow hawkweed has a shallow [113,117], fibrous root system [77,113,117]. One flora describes meadow hawkweed rhizomes as short and stout [49], while another describes them as short or, more often, elongated [31].

Density of meadow hawkweed populations is variable. It may establish at low cover (e.g., tussock grasslands in New Zealand [90] ), at dense cover (e.g., upland pastures in Idaho [15]), or in patches (e.g., old fields in New Jersey [1]).

A fact sheet suggests that meadow hawkweed may be allelopathic [77]. Laboratory studies showed that meadow hawkweed pollen could potentially limit the sexual reproduction of other plants by inhibiting pollination, seed germination, and/or seedling growth [74].

Impacts and control 10

More info for the terms: adventitious, cover, fire management, forbs, invasive species, natural, prescribed fire, presence, stolon, wildfire

Impacts: Meadow hawkweed has the potential to alter native plant communities. A fact sheet [77] and a weed management guide [117] report that individual plants may quickly develop into large, dense patches that displace other vegetation. In fields and pastures, meadow hawkweed may reduce forage quality [77,117]. It may also be problematic in lawns and gardens [77]. Meadow hawkweed may be allelopathic [74,77].

Control: Control of meadow hawkweed is complicated the presence of stolons, rhizomes, and adventitious root buds (see Vegetative regeneration), which may sprout following control treatments.

In all cases where invasive species are targeted for control, no matter what method is employed, the potential for other invasive species to fill their void must be considered [12]. Control of biotic invasions is most effective when it employs a long-term, ecosystem-wide strategy rather than a tactical approach focused on battling individual invaders [61].

Prevention: It is possible that meadow hawkweed establishment is facilitated by disturbance due to human activities. Distribution records from Montana documented meadow hawkweed establishing along a decommissioned road in an area burned by wildfire. It was not detected when the road was removed but was detected 6 years after road decommissioning [88]. Though dispersal mode was not identified, it is possible that meadow hawkweed could have been brought to the site via equipment related to road removal.

It is commonly argued that the most cost-efficient and effective method of managing invasive species is to prevent their establishment and spread by maintaining "healthy" natural communities 61,93 and by monitoring several times each year [45]. Managing to maintain the integrity of the native plant community and mitigate the factors enhancing ecosystem invasibility is likely to be more effective than managing solely to control the invader [41].

Weed prevention and control can be incorporated into many types of management plans, including those for logging and site preparation, grazing allotments, recreation management, research projects, road building and maintenance, and fire management [105]. See the Guide to noxious weed prevention practices [105] for specific guidelines in preventing the spread of weed seeds and propagules under different management conditions.

Fire: For information on the use of prescribed fire to control this species, see Fire Management Considerations.

Cultural control: A weed management guide suggests that cultural methods may be effective at controlling invasive hawkweeds in pastures and rangelands. Fertilizer application may enhance cultural methods by increasing nutrient availability to desired perennial grasses, legumes, or other preferred forbs [117]. In old fields in Michigan, 2 years of fertilization led to the expansion of Canada bluegrass and smooth brome and the elimination of meadow hawkweed [84]. In contrast, meadow hawkweed and other plants showed no clear response to fertilization treatments in an Idaho pasture [115]. The addition of fertilizer to herbicide treatments did not improve the level of meadow hawkweed control provided by herbicide treatment alone [113]. See Chemical control for more information on this study.

Physical or mechanical control: A fact sheet suggests that hand-pulling can be used on small infestations of meadow hawkweed if the entire root system is removed. Digging may control small infestations but may also stimulate the growth of new plants from rhizomes, stolons, and fragmented roots that are left behind [77]. A weed management guide also cautions that digging or other mechanical disturbances may prompt sprouting [117].

Mowing does not seem to be effective for controlling meadow hawkweed because it may encourage vegetative spread, and mower blades likely miss low-lying meadow hawkweed rosettes [77,117]. Meadow hawkweed occurred in frequently mowed fields in New Jersey, Pennsylvania [79], Michigan [84], and Wisconsin [107]. In field experiments in Idaho, sprouting from stolons and adventitious root buds and production of flowering stems were not limited by clipping. Plants recovered from clipping within a growing season. The production of daughter rosettes from the ends of stolons or satellite plants from adventitious root buds was also not affected by clipping. Flowering stem clipping reduced seed production by 23% and seed weight by 9% compared to unclipped plants [115]. A fact sheet [77] and weed management guide [117] suggest that mowing may reduce or prevent meadow hawkweed seed production.

A review of invasive plants reports that invasive hawkweeds do not persist with tillage, particularly where herbicide use and tillage are combined [22]. However, a fact sheet suggests that tilling may increase the spread of meadow hawkweed by redistributing fragmented roots, rhizomes, and stolons [77]. Physical disturbance by machinery may spread meadow hawkweed across fields. Local disturbances such as activity by livestock, wild ungulates, or rodents may also enhance its spread [117]. A fact sheet reports that careful grazing may suppress the growth and spread of meadow hawkweed, though overgrazing might increase its spread [77].

Biological control: Both insects [35,117] and fungi [117] were being evaluated for use in controlling meadow hawkweed and other invasive hawkweeds as of 2010. The presence of numerous native hawkweeds presents challenges to biocontrol programs. The stoloniferous character of invasive hawkweeds, a trait lacking in hawkweeds native to North America, suggests that biocontrol programs targeting stolons would be ideal. However, the inability of clipping experiments to reduce meadow hawkweed stolon and flowering stem production (see Physical or mechanical control) suggests that biocontrol agents targeting stolons may not be effective [115]. Meadow hawkweed plants experienced little insect herbivory in old fields in west-central New York, which the authors suggested could be due to the presence of hairs on the leaves [17].

Biological control of invasive species has a long history that indicates many factors must be considered before using biological controls. Refer to these sources: [109,118] and the Weed control methods handbook [102] for background information and important considerations for developing and implementing biological control programs.

Chemical control: Herbicides may control meadow hawkweed [15,53,54,77,94,113,116], though not in all cases (e.g., [94]). Herbicide application may be most effective early in the growing season, when plants are in the rosette stage, because treatment prevents flowering and seed production [77]. In Idaho, application of foliar herbicides to meadow hawkweed in either the spring, summer, or fall all prevented seed production 1 and 2 months after treatment [116].

In Idaho, one study investigated meadow hawkweed control using selective herbicides and a single fertilizer application across 3 levels of meadow hawkweed establishment (low (<25% cover), medium (40-60%), and high (>75%)) in cleared forestland converted to pasture. At all establishment levels, herbicide application resulted in almost complete control (<1% cover) of meadow hawkweed 3 months after treatment, with cover levels remaining at <1% 39 months after treatment. The addition of fertilizer to herbicide treatments did not appear to favor desired species at the expense of meadow hawkweed, and the combination of fertilizer and herbicide application did not increase perennial grass cover. The authors concluded that herbicide application alone was just as effective as the addition of fertilizers in the control of meadow hawkweed [113].

Herbicides are effective in gaining initial control of a new invasion or a severe infestation, but they are rarely a complete or long-term solution to weed management [14]. See the Weed control methods handbook [102] for considerations on the use of herbicides in natural areas and detailed information on specific chemicals. See the following sources for information specific to the chemical control of meadow hawkweed: [15,53,54,94,117]. Integrated management: No information is available on this topic.

Comments 11

Field Hawkweed is one of several native and non-native hawkweeds (Hieracium spp.) that can be found in Illinois. Like other non-native hawkweeds, this species has primarily basal leaves and very few, if any, cauline leaves. Field Hawkweed can be distinguished from other non-native hawkweeds by its dense cluster of flowerheads and the presence of hair on both sides of its basal leaves. Other non-native hawkweeds have flowerheads that are more widely spread out, or their basal leaves have hairs along the lower side only, or the branches of their inflorescences lack glandular black hairs. One non-native species that is found in Illinois, Hieracium aurantiacum (Orange Hawkweed), can be readily distinguished by its orange flowerheads. Another scientific name of Field Hawkweed is Hieracium pratense. This species is sometimes referred to as 'King Devil' or 'Yellow King Devil.' These are old farmer names that refer to its unwelcome persistence in pastures and agricultural fields.

Sources and Credits

  1. (c) Anita, some rights reserved (CC BY-NC-SA), http://www.flickr.com/photos/61897811@N00/3643033122
  2. (c) Richard Spellenberg, some rights reserved (CC BY-NC-SA), https://calphotos.berkeley.edu/imgs/512x768/0000_0000/0412/1133.jpeg
  3. (c) anonymous, some rights reserved (CC BY-NC), http://www.biopix.com/photos/jcs-pilosella-aurantiaca-ssp-dimorpha-07397.jpg
  4. (c) RT Hawke, some rights reserved (CC BY-NC), https://calphotos.berkeley.edu/imgs/512x768/0000_0000/0912/0888.jpeg
  5. (c) anonymous, some rights reserved (CC BY-NC), http://www.illinoiswildflowers.info/weeds/photos/fld_hawk1.jpg
  6. (c) anonymous, some rights reserved (CC BY-NC), http://www.illinoiswildflowers.info/weeds/photos/fld_hawk2.jpg
  7. (c) Matthew Salkiewicz, some rights reserved (CC BY-NC), uploaded by Matthew Salkiewicz
  8. (c) aldric, some rights reserved (CC BY-NC)
  9. Public Domain, http://eol.org/data_objects/24629183
  10. Public Domain, http://eol.org/data_objects/24629200
  11. (c) John Hilty, some rights reserved (CC BY-NC), http://eol.org/data_objects/29586551

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