sweet vernalgrass (Anthoxanthum odoratum)
scented vernal grass
sweet vernal grass
sweet-scented vernal grass
TAXONOMY: The currently accepted scientific name for sweet vernal-
grass is Anthoxanthum odoratum L.
NATIVE STATUS: Introduced, United States and Canada.
GENERAL BOTANICAL CHARACTERISTICS: Sweet vernalgrass
is a tufted, long-lived (i.e. perennial), grass usually growing 10-80 cm tall,
but occasionally reaching up to 1 m in height. The upright (i.e. erect) flow-
ering stems (i.e. culms) are slender, hairless (i.e. glabrous) and unbranched.
The leaves consist of a leaf sheath, which partially encloses the stem, and
a spreading leaf blade. The leaf blades (1-31cm long and 1.5-9 mm wide)
are rolled when developing, but flatten out as they mature. They are entire
with long-pointed tips (i.e. acuminate apices) and are hairless (i.e. glabrous) or have some scattered hairs (i.e. sparsely pubescent) on both surfaces.
Where the leaf sheath meets the leaf blade there is a small membranous
structure (i.e. ligule) 1-5 mm long. The seed-head is a narrow spike-like
cluster (i.e. spiciform panicle) and is borne at the tips of the stems. These
seed-heads (1-12 cm long and 0.7-2 cm wide) consist of numerous flower spikelets (6-10 mm long) that are borne on very short stalks (i.e. pedicels)
0.5-1 mm long. Each flower spikelet has a pair of bracts (i.e. glumes) at
the base, one of which is about twice as large as the other. They are some-
what hairy and have a single tiny flower (i.e. floret) topped with a small
bent awn (6-9 mm long). These tiny flowers have two floral bracts (i.e. a
lemma and palea) and both male and female flower parts (i.e. three sta-
mens and an ovary topped with a style and two-branched stigma). The
flower spikelets turn from green to light brown or straw-coloured as they
mature and break apart above from the seed-heads above their bracts (i.e.
glumes). The 'seed' (i.e. caryopsis or grain) remains contained within the
other floral parts. Sweet vernalgrass species also gives off a strong scent
of freshly-mown grass. The scent is particularly strong when dried, and is
due to coumarin, a glycoside, and benzoic acid – it smells like fresh hay
with a hint of vanilla. The roots are quite shallow, absorbing nutrients
mainly from the upper 10 cm of soil. Like many other grasses, sweet ver-
nal grass contains allelopathic chemicals that suppress the growth of other
plant species. However, old roots appear to enhance the growth of other
grass species, while decreasing the growth of new Anthoxanthum plants. Phosphorus content in the roots averaged 0.155%, a relatively high level.
This is probably one of the factors leading to the increased growth of other
species on sites with decomposing sweet vernal grass roots.
REGENERATION PROCESS: Sweet vernalgrass propogates itself by
reseeding flowering early in the spring and forming distinct, identifiable
clumps that do not spread vegetatively. The seeds are commonly dispersed
by wind, water, animals and vehicles. They may also be spread in contam-
inated agricultural produce, particularly fodder, and in dumped garden
HABITAT TYPES: Commonly a weed of pastures, roadsides, disturbed
sites and waste areas. It also invades coastal environs, heathlands, heathy woodlands, meadows and fields, grasslands, open woodlands, forest edges,
moist forests, riparian vegetation, freshwater wetlands, alpine and sub-al-
pine vegetation and cliffs, balds, ridges or ledges.
SITE CHARACTERISTICS: Sweet vernal grass grows well on poor
soils. It commonly occurs on soils that are low in phosphorus. Sweet ver-
nal grass also shows a remarkable ability to genetically adapt to different environmental conditions.
SEASONAL DEVELOPMENT: Seedheads develop around April and
May and give off a sweet smell.
GENERAL DISTRIBUTION: Sweet vernalgrass ranges from northern
Florida to southern Canada along the East Coast and west to the Mississippi
River flood plain. It also occurs from northern California to Vancouver Is-
land, Canada. It was introduced to North America from Europe in the late
1700s as a meadow grass and has since escaped cultivation.
SKY MEADOWS DISTRIBUTION:
Grass specimens can be found on trails marked in red.
Appalachian Trail/Old Trail
South Ridge/North Ridge
Rolling Meadows/ Lost Mountain
The specific distribution of sweet vernalgrass has not been determined.
IMPORTANCES AND USES: Sweet vernalgrass has often been includ-
ed in hay and pasture mixtures for its fragrance, but since it was discovered
that cattle find it unpalatable, this practice is waning.
Native Americans used large sweet grass to make baskets.
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