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Hoary Alyssum
Berteroa incana
L.
Mustard
Family |
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Key identifying traits
Flowers are white with 4 petals, deeply divided
Usually only branched at the top of the plant
Leaves are alternate, blades are simple
Fruit is oblong, with two compartments containing 2 to 6
seeds
Seeds grow close to stem, are round to oblong, narrowly
winged, grayish-brown and rough
Biology and ecology
- Can be an annual, winter annual, biennial, or a
short-lived perennial (!)
- Most abundant in disturbed sites but is also found in
meadows and pastures
- Starting to be an invader in alfalfa crops
- 1 to 2 ½ feet tall
- Can be toxic to horses if it comprises 30% or more of
their diet
- Spreads rapidly due to the high number of seeds per plant;
spreads only by seed
- Likes direct sunlight but can also tolerate shade
Control
Prevention – Learn to
identify plants; know your property; beware of fill dirt, hay
and seed from outside your area
Biological – No known biological control
Cultural – Good vegetative cover helps but does not
prevent establishment or spread
Mechanical –
Hand
pulling or digging can be very effective for small infestations
but should be done before there are seed pods. Mowing is not a
good control option; plants tend to start growing flat along the
ground.
Chemical – Several effective at label rates but may
require more than one application. If in flower, it can still be
effectively controlled with appropriate herbicides.
The
PNW Weed Management Handbook does not have this weed listed for
control recommendations, but other annual mustard
recommendations may be useful. Telar and Escort are
effective on most mustards and adding 2,4-D can help stop seed
viability when plants are in bloom |
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seeds pods & flowers
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Hoary alyssum on street corner
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Hoary alyssum in tree planting
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Hoary alyssum on a mountain road
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Where found –
Largest infestations in the
county are in Colville, Arden, Chewelah and Northport areas but Hoary alyssum is
spreading rapidly.
MSdoc
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