Holosteum umbellatum
Holosteum
jagged-chickweed, umbellate chickweed
holosteum, jagged chickweed
slender.
ascending to erect, simple or branched, terete.
forming basal rosette, connate proximally into sheath, petiolate (proximal leaves) or sessile (cauline leaves);
blade 1-veined, oblanceolate to spatulate (proximal leaves) or elliptic to ovate (cauline leaves), somewhat succulent, apex acute.
terminal, umbellate cymes, sometimes not yet developed in young individuals, then with 2–4 bracts and often buds at base of pedicel;
bracts clustered, foliaceous with scarious margins to entirely scarious.
reflexed after flowering, erect in fruit.
bisexual or occasionally unisexual and pistillate;
perianth and androecium hypogynous;
sepals 5, distinct, green, lanceolate to ovate, 2.5–4.5 mm, herbaceous, margins white, scarious, apex acute to obtuse, not hooded;
petals 5, white to pink, clawed, blade apex jagged but not 2-fid;
nectaries not apparent;
stamens 3–5, arising from base of ovary;
filaments distinct nearly to base;
staminodes absent;
styles 3(–5), clavate to filiform, 0.5–1.5 mm, glabrous proximally;
stigmas 3(–5), subterminal to linear along adaxial surface of styles, minutely papillate (50x).
ovoid to cylindric, opening by 6 (rarely 8 or 10) revolute teeth;
carpophore absent.
35–60, orange to brown, oblong, shield-shaped, dorsiventrally compressed, papillate, marginal wing absent, appendage absent;
embryo central, straight.
= 10.
Holosteum umbellatum
Holosteum
Subspecies 5 (1 in the flora).
L. H. Shinners (1965) demonstrated that Holosteum umbellatum has been introduced in North America on several occasions. Collections from northeastern North America are mainly older ones from very localized populations, the first from near Lancaster, Pennsylvania, in 1856. Reports from the central United States show its occurrence there in several states in the 1940s, spreading rapidly along roadsides, railroads, and other calcareous sites. M. L. Fernald (1943f) suggested that H. umbellatum may have been spread as a contaminant in grass seed sown after highway construction in Virginia (see 34.2. Petrorhagia prolifera and 34.4. P. dubia for similar cases). The first collection from the western United States was made in 1926 and the species has since spread to various disturbed sites in the Pacific Northwest. Several plants in two recent collections from Oregon (e.g., Joyal 463, OSC) are infected with an ovary smut (Microbotryum sp.), the first evidence of such infection on Holosteum in North America known to us.
The early appearance and extremely brief life cycle of Holosteum umbellatum probably contribute to its being overlooked. It should be expected elsewhere in our range.
(Discussion copyrighted by Flora of North America; reprinted with permission.)
Species 3–4 (1 in the flora).
(Discussion copyrighted by Flora of North America; reprinted with permission.)
- Local floras:
BC, 
OR, 
WA - Local Web sites:
CalFlora, CalPhotos, 
Flora NW, 
Go Botany, 
IL Wildflowers, 
KS Wildflowers, 
MD Biodiversity, 
MI Flora, 
MO Plants, 
PNW Herbaria, Turner Photog. 
WildflowerSearch
iNaturalist (observations)
USDA Plants Database- LBJ Wildflower Center
- SEINet
- Plants of the World Online
- Encyclopedia of Life
- Wikipedia
- Google Image Search
