Hieracium piloselloides (Glaucous King-devil)

Plant Info
Also known as: Smooth Hawkweed, Tall Hawkweed, King-devil Hawkweed
Family:Asteraceae (Aster)
Life cycle:perennial
  • Invasive - ERADICATE!
Habitat:part shade, sun; open fields, roadsides, disturbed soil, high grade prairie
Bloom season:June - August
Plant height:12 to 40 inches
Wetland Indicator Status:none
MN county distribution (click map to enlarge):Minnesota county distribution map
National distribution (click map to enlarge):National distribution map

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Detailed Information

Flower: Flower shape: 7+petals Cluster type: flat Cluster type: panicle

[photo of flowers] A cluster of 5 to 30+ dandelion-like flowers at the top of the stem. The cluster may start out compact with the flower stalks elongating with age. Flowers are yellow, about ½ inch diameter with 40 to 80 rays (petals).

[photo of phyllaries] The bracts (phyllaries) surrounding the base of the flower are about ¼ inch (to 7 mm) long and covered in a mix of tiny star-shaped hairs, long, spreading white hairs, and black hairs that may or may not be gland-tipped. Flower stalks may be similarly hairy.

Leaves and stems: Leaf attachment: alternate Leaf attachment: basal Leaf type: simple

[photo of basal leaves] Leaves are mostly basal, 1 to 6 inches (to 15 cm) long, 1/3 to ~1 inch (8 to 20+ mm) wide, lance-elliptic to narrowly spatula-shaped, rounded to pointed at the tip, toothless or minutely toothed along the edges. Both leaf surfaces are mostly hairless, sometimes with sparse long hairs on the upper surface, along the edges, and/or along the midvein on the underside. 

[photo of stem leaves] Stem leaves are smaller, mostly broadest above the middle and typically number 1 or 2 but sometimes more or absent altogether. Flowering stems are single, unbranched and variably covered in a mix of star-shaped hairs, long spreading hairs, and shorter glandular hairs, though the upper stem is often hairless or nearly so. Rhizomes and stolons (runners) are absent.

Fruit: Fruit type: seed with plume

Fruit is a dark seed with a tuft of dull white hair to carry it off in the wind.


A relative new-comer in many parts of the state, Glaucous King-devil, known as Smooth Hawkweed in some references, has expanded in all directions from the Duluth area over the past 30+ years along with other weedy non-native Hawkweeds. This species is not as prolific as some others but they often grow together. It is not uncommon to see entire abandoned hay meadows and road ditches completely overrun with yellow and orange Hawkweeds, but all are known to invade high grade habitat as well.

The common name Smooth Hawkweed is a misnomer, since no parts of the plant are always completely smooth. The phyllaries are covered in a mix of star-shaped hairs, black glandular hairs and long spreading hairs; leaves may have long hairs along the edges and the midrib on the underside, sometimes a few long hairs on the upper surface, and stems are covered in star-shaped hairs, sparse glandular hairs, and/or long spreading hairs, though may be hairless or nearly so on the upper stem. It most closely resembles Meadow Hawkweed (Hieracium caespitosum), which is most easily distinguished by its abundant star-shaped hairs on leaf surfaces, but its leaves are typically also larger and stems hairier.

There are dozens of reports of this species on iNaturalist, a number of which cannot be confirmed from the posted images. A common mis-identification is confusing it with Hieracium umbellatum, which is easily distinguished by the numerous stem leaves that are irregularly toothy, lack of basal leaves, and brown hairs on the seeds. The weedy Sowthistles (Sonchus spp.) also have yellow dandelion-type flowers but are much larger and the leaf shape is very different: lobed and/or toothy and sometimes clasping. Narrow-leaf Hawksbeard (Crepis tectorum) is another weed with yellow dandelion-type flowers but lacks the long spreading and glandular hairs, and stem leaves are more numerous and variable in shape, often linear.

Note that the trend seems to be switching Hieracium species that (mostly) lack stem leaves over to genus Pilosella; it includes all of the weedy non-natives, but this change hasn't been adopted in Minnesota (yet).

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More photos

Photos by K. Chayka taken in Cook and Pine counties. Photos by Peter M. Dziuk taken in Lake and Pine counties.


Have you seen this plant in Minnesota, or have any other comments about it?

Posted by: Molly Turner - BEMIDJI
on: 2018-06-21 14:56:45

I believe this is what is growing in the part of our yard that we chose not to mow this year.

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