Field pennycrest is an annual weed and member of the mustard family, Crucifereae, that also includes cabbage, broccoli, and sweet alyssum.  It is a native of Eurasia but was introduced into the US by 1701 and is now naturalized in all of the 48 contiguous states.  Plant prefer full sun, medium moist, fertile, slightly acid soil and can be found in meadows, fallow fields, croplands, grasslands, gardens, nursery plots, roadsides, railroad right-of-ways,  and waste lands.  

Description:  Young plants form a rosette of leaves up to six inches across and develop a central stem with several side stems.  The leafy stems grow up to twenty four inches tall and  are ribbed with wings along some of the ribs.  The leaves on the stem are  alternate, arrow-shaped,  and narrow and  have  slightly wavy margins with a few blunt teeth.  They are hairless, up to four inches long, and have a garlic-like odor when crushed.  The lower leaves have short petioles or clasp the stem while those  in the middle or upper part of the stem have a pair of lobe-like projections that clasp the stem.  The flowers are carried in flat-topped terminal racemes on both the main stem and upper side stems,  and elongate when in fruit.  They appear from mid-spring to late summer, and  are 1/8″ across and have four white petals. The fruit is 1/2″ long round flat seed pod with a membranous wing and resembles an old English penny hence the common name pennycress.  A single plant can produce up to 20,000 seeds/year that can remain viable in the soil for up to thirty years.  Plants reproduce by seed.

Control: Mulch to discourage sprouting of existing seeds in the seed bank.  Pull or hoe young seedlings and dig or mow older plants before they go to seed.  Do not till the soil as it will move seeds in the seed bank to upper parts of the soil where they can readily germinate.  In severe cases herbicides can be used:  good control has been achieved with 2,4 D and MCPA.

 

Photo Credits:

Acker Hellerkraut, Wikimedia

Matt Lavin, Wikimedia

 

 

By Karen