Name: Berteroa incana
Common Names: hoary alyssum, false hoary madwort, hoary
History: Hoary alyssum is an annual, or short lived
perennial that originated from Europe and Asia. It is believed
that it reached North America in contaminated alfalfa and clover
seed. In Montana, hoary alyssum was first found in Gallatin
county in 1905.
Roots: Hoary alyssum has a long, slender, tap root.
Stems and Leaves: Hoary alyssum has a basal rosette with
oval or lance shaped leaves that are three to five cm long. The
plant can have one or more flowering stems that are 20 to 70 cm
tall and usually branch at the top. Leaves on the stem grow
alternately, upward, and they are smooth edged like the basal
rosette leaves. The stems and leaves are covered in tiny, star
shaped, gray hairs giving the plant a gray appearance.
Flowers and Seeds: The flowers bloom early spring to late
fall depending on the amount of water they receive. The flowers
are small, white, and have four petals. The petals are narrow
towards the bottom and have a distinct notch in the top of them.
There are two short outer stamens and four long inner stamens
that are bright yellow. The seeds are contained within seedpods
that are five to eight mm long. In each pod there are four to
twelve dark, reddish brown, lens shaped, seeds that are one to
two mm long.
Methods of Reproduction: Hoary alyssum reproduces only
through its seeds. The seeds can remain viable in the soil for
up to nine years.
Environments Favorable for Infestation: Hoary alyssum
likes to infest dry, low nutrient, disturbed ground, like
roadsides, trails, vacant lots, lake and stream beds, lawns, and
Environmental Impacts: Hoary alyssum is not palatable to
livestock because of its woody stock therefor, decreasing forage
in pastures and fields. In large amounts (30 to70%) it is
toxic to horses and can cause swelling in the lower legs, fever,
diarrhea, and in extreme cases death.
Range: Hoary alyssum occurs in 38 of the lower 48 states
and in Montana it infests 27 of our 56 counties as of 2015.
Prevention: All equipment and vehicles must be carefully
washed off after traveling through an area where hoary alyssum
occurs to prevent spreading the weed seeds.
Mechanical: Hand pulling, mowing, (mowers must be
carefully cleaned after) and tilling repeatedly can be effective
Cultural: Goats and sheep have not been used to graze
hoary alyssum although they will eat it.
Biological: There is not currently a bio-control agent
approved for use in the U.S.
Chemical: Opensight, Chapparal, Payload, Broadstar, and 2
4-D have been useful in controlling hoary alyssum.
Other: Prescribed burning, re-vegetation, and
irrigation have shown successful results in controlling hoary
1."Biology, Ecology, and Management of Hoary Alyssum." NRCS.
Web. 13 Aug. 2015. <http://www.nrcs.usda.gov/Internet/FSE_PLANTMATERIALS/publications/mtpmstn8346.pdf>.
2. "Biology, Ecology, and Management of Hoary Alyssum." Web. 13
Aug. 2015. <http://store.msuextension.org/publications/AgandNaturalResources/EB0194.pdf>.
3. "Hoary Alyssum." : University of Minnesota Extension.
Web. 13 Aug. 2015. <http://www.extension.umn.edu/agriculture/horse/pasture/hoary-alyssum/>.
4. "Montana Weed Control Association." Montana Weed
Control Association. Web. 13 Aug. 2015. <http://mtweed.org/weeds/hoary-alyssum/>.
5. "Plant Fact Sheet." Web. 13 Aug. 2015. <http://plants.usda.gov/factsheet/pdf/fs_bein2.pdf>.
6. Web. 13 Aug. 2015. <http://www.pestid.msu.edu/wp-content/uploads/2014/07/HoaryAlyssum.pdf>.
8/13/15 By: Alycia
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