II
E. K. PARKER
Shoestring Weed
LAWRENCE jENKINS
E. R. jACKMAN
SHOESTRING WEED
Psoralea lanceolata
Showing entire plant at bloom stage.
Oregon State System of Higher Education
Federal Cooperative Extension Service
Oregon State College
Extension Bulletin 563
Corvallis
November 1941
Shoestring Weed
(Psoralea lanceolata)
By LAWRENCE JENKINS and E. R. JAcKmAN*
Illustrations by Cathrine Davis Young
Shoestring weed is one of the newer weeds in Oregon, so far reported in
six eastern Oregon counties. Occasionally it is found on cultivated land but
generally infests waste places and roadsides. The plant commonly grows from
10 inches to 2 feet tall. It closely resembles alfalfa in appearance but has a
strong, offensive odor. Judging from limited observations, it is not eaten by
livestock. Leaflets are produced in groups of three, about the same size and
shape as those of alfalfa. The plant grows from large, creeping roots that are
dark brown, long, and toughhence the name, "shoestring." Leaves and stems
are speckled with dark brown to black raised glands that produce a resinous,
sticky substance. The glands are about the size of pin points. Flowers are purple to white and are borne in compact clusters on slender stems arising in the
axils formed by the leaf stems and main stem. Plants observed in Oregon
produce very little mature seed as blossoms drop before seed has formed. Seed
is about the same size as that of alfalfa and is produced singly in small pods.
Control. Little is known regarding the control of this pest. It apparently
is quite resistant to cultivation. Judging by its deep and extensive, tough root
system, probably two seasons of summer fallow will be required to control it
completely. The plant is late in maturing, so an annual hay crop could be
harvested from the land, followed by deep plowing and summer fallow the
balance of the season. Limited trials using sodium chlorate on this pest have
not given good control. Most of the patches in the state are small ; therefore
carbon bisulphide appears to offer the most promise. This chemical should be
applied at the rate of 2 ounces per hole in holes 5 to 6 inches deep and 18
inches apart in staggered rows. The holes should be closed immediately after
treating.
Carbon bisulphide is a liquid that forms a gas that kills the roots. In dry
soil this gas sometimes evaporates from the soil too fast. Tar paper covering
over the treated area has been used to slow down this evaporation from the
surface with varying degrees of success.
Extension Bulletin 510 contains a detailed discussion on the use of carbon
bisulphide and other methods of controlling perennial weeds.
This is one of a series of 39 bulletins discussing 58 perennial weeds in
Oregon and their control. A list of bulletins in this series will be found on the
last page of Extension Bulletin 510. The individual bulletins are punched so
that several may be bound together if desired.
ACKNOWLEDGMENTS: The authors thank Dr. Helen M.Gilkey, Curator of the HerR. Hyslop, In Charge, Division of Plant Industries, made many helpful suggestions.
barium, for reading the manuscript and checking the description of the plant. Professor
G.
E. R. Jackman is Extension Specialist in Farm Crops and Lawrence Jenkins is
Assistant Extension Specialist in Farm Crops at Oregon State College.
Cooperative Extension Work in Agriculture and Home Economics
Wm. A. Schoenfeld, Director
Oregon State College and United States Department of Agriculture, Cooperating
Printed and distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914