mouse-ear hawkweed (Hieracium pilosella)
Pilosella officinarum (L.) F.W.Schultz & Sch. Bip.
Like most hawkweed species, it shows tremendous variation and is a com-
plex of several dozens subspecies and hundreds of varieties and forms,
each with their own scientific names and synonyms. As would be antic-
ipated Hieracium pilosella has a very large number of synonyms, many
based on European studies. Pilosella officinarum is the synonym most
likely to be encountered in most North American references.
CONFIRMATION STATUS: Pending confirmation.
TAXONOMY: The currently accepted scientific name for mouse-ear
hawkweed is Hieracium pilosella L. There are two varieties of Hieracium
pilosella found in the United States: 1) variety pilosella, and 2) variety
niveum Müll. Arg. Variety niveium has a restricted distribution in the New
England region. Only variety pilosella is reported as occurring in Virginia.
NATIVE STATUS: Introduced, United States and Canada.
GENERAL BOTANICAL CHARACTERISTICS:
Habit: Mouse-ear hawkweed is a low-growing, perennial plant with flow-
ering stems rising 6 to 8 inches. The whole plant, with the exception of the
flower parts, is covered in glandular hairs, usually whitish, sometimes red-
dish on the stem. The scape is leafless and glandular.
Leaves: This hawkweed grows from a basal rosette of leaves, the rosette
leaves being entire, elliptic in outline, acute to blunt with the underside of
the leaves covered with hair. All leaves have a distinctive white midvein
and are generally between 1 1/4 to 4 inches long, reaching 3/4 inches in
Flowers: The flowering stem (scape) sprouts from the centre of the basal
rosette. It is usually much taller than the leaves. The flowerheads are borne
singly on the scape and are a pale lemon-yellow colour, with the outermost
ligules having a reddish underside. The flower heads are approximately 1
inch across, with bracts surrounding the flower head covered with black
hairs and glands. In general, the flowers resemble dandelion.
Fruit/Seeds: The fruit is an achene with slender bristles.
Roots: The root system is comprised of fibrous roots and stolons. The
stolons can generate a new rosette at their extremity, each rosette has the
possibility of developing into a new clone forming dense mats in open
REGENERATION PROCESS: Mouse-ear hawkweed propogates it-
self by reseeding and through stolon spread, often forming a large mat
of "plants" that are really derived from a single source.
HABITAT TYPES: Mouseear hawkweed is primarily a weed of turf-
grass, lawns, pastures, hayfields, and roadsides. It does best in disturbed
areas, where it can compete better against other early successional plants.
SITE CHARACTERISTICS: Mouse-ear hawkweed prefers dry, sunny
areas. It grows well on sandy and similarly less fertile ground types, par-
ticulary in disturbed or waste areas.
SEASONAL DEVELOPMENT: Mouse-ear hawkweed flowers from
May until August.
GENERAL DISTRIBUTION: Mouse-ear hawkweed is a plant of two
widely separated parts of the United States and Canada. First, it is found
throughout the New England and mid-Atlantic states as far south as
Georgia (although not reported from South Carolina), and extends as far
west as Tennessee and Kentucky. It reappears in Michigan and Minnesota
and can found throughout the Canadian maritime provinces, extending
west through Quebec and Ontario. The second part of the United States
and Canada where it occurs is the far northwest, ranging north from Ore-
gon, Washington, British Columbia inot Alaska.
SKY MEADOWS DISTRIBUTION: To be determined.
Mouse-ear hawkweed is probably a recent arrival to Sky Meadows State
Park and, possibly, to Facquier County. It is not currently listed as occur-
ring in Facquier County by the Department of Agriculture's PLANTS
Database, although it does occur in adjacent Rappahannock County and
in several other Virginia counties (e.g., Fairfax).
IMPORTANCE AND USES: There is insufficient information currently
available concerning the wildlife value of mouse-ear hawkweed. However,
as a species of the Hawkweed genus, it is probably used as a food plants by
the larvae of some Lepidoptera species. Some Hawkweed Genus visitors
include autumnal rustic, broad-barred white, dot moth, Hebrew character,
large yellow underwing, lime-speck pug, the shark, the grass moth Dia-
semia reticularis, and also by small beetles.
The mouse-ear hawkweed contains umbelliferone, a known antibiotic
against brucellosis, a highly contagious disease caused by ingestion of
unsterilized milk or meat from infected animals or close contact with
their secretions. Umbelliferone is also a frequent active compound in
sunscreen lotions. The plant is also a potent diuretic.
Crooked Run Valley