White Hawkweed
Species profile by Wendy Aeschliman
Differentiating between the native hawkweeds and the exotic/ noxious weed species is not at all easy. This, the native white hawkweed, is one species which is easy to differentiate from the invasive exotic species. Why? It is the only hawkweed with whiteflowers.
Common Name(s): White Hawkweed
Scientific Name: Hiericium albiflorum
General Info: Hawkweeds (Hiericium )are an exceedingly complex genus, challenging for even the professional botanists. Here are some common charactistics of hawkweeds:
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All hawkweeds are perennials that regrow from underground rhizomes.
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All hawkweeds can, when damaged, exude milky sap.
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Flowerheads are of the composite form, similar to dandelion. Flowerheads are composed of numerous individual flowers composed of ray flowers (strap-shaped petals), slightly notched.
The white hawkweed can grow to 3-4 feet (to 120 cm) . It is non toxic to nearby plants and non toxic to livestock.
Native/ Non-native: Native. (There are also native yellow flowered species, as well as exotic yellow species....)
Ecology: Widespread in dry open foothill areas up into subalpine forests. It has high drought tolerance, intermediate shade tolerance.
Range: Western U.S. and Canada, generally. (Disjunctive populations can occur elsewhere.) Populations are found from southeastern Alaska to Saskatchewan and south to California, Colorado, and northern Mexico.
Leaves/Stem: Slightly to moderately hairy, 2 to 7 in long (5 to 13 cm). Stem leaves are reduced in size, but not to the degree as found in the exotics. Lower stem and basal leaves are relatively wide as compared to the exotics. Basal leaves, rather than long and narrow, are almost oval in shape. Stems are hairy near base, less hairy to hairless above.
Flowers: Composite, with individual flowers composed of strap-shaped petals. Blooms in late spring to summer. Inflorescence is rather open as compared to exotic hawkweeds.
Fruits: One seeded fruit, like dandelion (Achene, pronounced A keen’). Like the dandelion, the seeds blow away in the wind after drying. Fruit/seed abundance is low.
Notes:
1) If you find an orange hawkweed, it is exotic/ invasive. If you find a yellow hawkweed it could be either native or invasive; it is best to do your research. If you find a white hawkweed, it is native.
2) Any hawkweed with stolens, like strawberry runners, is exotic! Exotic species with stolens are generally capable of establishing infestations of high densities, especially in disturbed areas. The natives reproduce from underground rhizomes only, and generally are not found in high densities.
3) The name hawkweed (Hiericium) comes from Greek hierax, stemming from the belief of the ancient Greeks that hawks would tear apart the plant and use the milky sap to clear their eyesight. Albiflorum means white flower.
Resources/ Links:
A resource on Montana hawkweeds, both exotic and native:
http://msuextension.org/publications/AgandNaturalResources/EB0187.pdf
http://www.gardenguides.com/taxonomy/white-hawkweed-hieracium-albiflorum/
Field Guide to Forest Plants of Northern Idaho (Patterson, Neiman, Tonn), 1985 USDA – Forest Service
Plants of Southern Interior British Colombia and the Inland Northwest (Parish, Coupe, Lloyd), 1996
Above:White hawkweed flowers are composite, open, and small.
Below: Basal leaves are relatively wide as compared to the exotics, and can be oval shaped. Stem leaves are reduced in size but not as much as the exotic invasive hawkweeds. Note hairs on lower stem and leaves.
White petals are ray florets, slightly notched. There are no disk flowers.
Photos by Wendy Aeschliman