Blue mustard (Chorispora tenella) is an invasive plant that has found a new home it really likes. Each spring, countless vacant lots, fallow fields, and roadsides are blanketed in the pale purple hues of Chorispora. The color lasts for weeks as the plants grow, up to several feet tall, and new flowers emerge.

Blue mustard hails from Russia. Experts aren't sure when it first arrived, but in 1929 it was spotted in Idaho. Here it has all the comforts of home, full sun, dry climate, and poor soil-few natural insects and diseases to curb its growth. This adventive weed wasted no time taking over disturbed areas and spreading rapidly throughout the west.

Blue mustard is an annual that germinates in late fall or early winter. It overwinters in a rosette and resumes active growth in the spring.

It is a leafy herbaceous plant that has a spreading habit. Stems and leaves, covered in tiny gland-tipped hairs, are sticky. It has a nasty odor, a smell similar to discovering your child's melted crayon in the dyer or on your dashboard.

Rosettes, with deeply lobed leaves, look like dandelions. As plants mature, leaves become less deeply indented. Leaves are about 1 to 3 inches long with stalk lengths decreasing from the base to the top of the plant.

Small purple flowers bloom from March to May. Like all mustards, flowers have 4 petals that form the shape of a Maltese cross. Small bean-like seed pods break crosswise, into two pieces, rather than splitting lengthwise down the pods.

Because it germinates in the fall, this weed is prepared to take springtime moisture away from slower starting plants. Most native plants and crops are no match for blue mustard. Dairy animals grazing it are likely to produce foul tasting milk.

Once in bloom, plants can produce seed in 10 days. Seed is produced in large quantities and remains viable in the soil for 5 years or more.

Small patches of blue mustard, and many other annual weeds, can be managed by handpulling. It has a shallow taproot and is easily removed. Applying organic mulches, like bark or compost, helps prevent blue mustard from invading your yard. For more information on control methods, please visit http://www.ext.colostate.edu/ptlk/2119.html

For information on other natural resource issues, call the Jefferson Conservation District at 720.544.2870. The mission of the district is to protect our natural resources through education and environmental awareness. Karen Berry is a member of the Jefferson Conservation District and the Wheat Ridge City Council.