Lead Plant: Amorpha canescens
Charles Umbanhowar Jr., Spring 1998, Minnesota Plant Press 17(3)
Lead plant ( Amorpha
canescens Pursh ) is one of the few native shrubs on the prairies of Minnesota. The
common name may refer to the grayish color of the leaves or perhaps to an old belief that
the plant was an indicator of lead ore deposits. Amorpha comes from the Greek
amorphos meaning 'without shape or deformed" in reference to the small (-1/4 inch)
flower which is reduced to a single petal; and canescens is Latin meaning
'gray-hairy". Lead plant is widely distributed throughout the prairies of Minnesota
especially in mesic or dry areas. Individuals grow 1 to 2 feet tall. They are shrubby,
meaning they have woody stems and their buds are above the ground, but they can bud from
ground level if plants are burned or grazed. A member of the bean family, the leaves are
compound, like most legumes, are 2 to 4 inches long, and are composed of - 25 pairs of
grayish leaflets along a single axis (rachis). Flowers are born on several terminal
spikes. An individual spike may contain 50 to 100 flowers. The massing of so many small flowers
and the contrast of the single purple petal and yellow stamens of each flower can only be
appreciated at close range but it is one of the great joys of viewing this plant. When
pollinated each flower produces a single seed, borne in a small, gray hairy pod. Seeds
require both a cold period and heat to germinate. Heat can be provided by pouring boiling
water over the seeds and then allowing the water to cool.
As a legume, lead plant is a host to nitrogen-fixing
bacteria in its roots. The bacteria provide the plant with nitrogen in exchange for sugars
that the plant produces through photosynthesis. These bacteria are available as inoculum
from most native-seed suppliers. Intensive grazing will reduce the abundance of lead
plant, and it does not tolerate cultivation. Periodic burning reduces plant size but
increases plant number-a pattern found for many prairie legumes. I often use the presence
of large lead plants or old, dead stems as a sign that an area has not been burned in the
last several years.
Lead plant is one of 15 species of Amorpha present in
the United States, and one of 3 species in Minnesota. False indigo (Amorpha fruticosa)
grows 5 to 6 feet tall, and the leaflets are larger and seem to be less hairy than those
of lead plant. Dwarf wild indigo (Amorpha nana) is found in the western, dry
prairies of Minnesota. It is more diminutive in stature (-l foot tall), and the leaflets
are greener and more rounded.
Lead plant and the other Amorphas have been used
medicinally by Native Americans who called it "buffalo bellow plant' because it
bloomed coincident with the rutting of bison. Drunk as a tea or smoked, the plant was used
to treat ailments as varied as pinworms, eczema, and rheumatism.
Size: 3 inch cluster
Date: Early June
Leadplant (Amorpha canescens)
The beautiful dark purple spikes of leadplant should be
appearing now on the North Dakota prairies. Leadplant is primarily a plains dweller but
also occurs in sandy open woods as far east as Michigan and Indiana.
This plant may reach forty inches in height but usually
is about a foot and a half tall in our area. The plant gets its colloquial name from the
gray appearance caused by fine hairs which cover the leaves stems and unopened flowers.
Flowering spikes are crowded at the top of the stems. Each spike produces nearly a hundred
tiny flowers. Leaves are composed of about twenty pairs of oval leaflets. The thick
taproot of this perennial plant penetrates deep underground. At maturity the seedpods
(legumes) are about three-sixteenths of an inch long.
Leadplant is fairly common on most native prairies in
eastern North Dakota. The plant seems to reach best development on east- and southfacing
slopes. Leadplant is good livestock forage as indicated by a two to tenfold reduction in
coverage of the plant on heavily grazed pastures as compared to those moderately or
lightly grazed. When long-idle native prairie dominated by introduced grasses is burned in
the spring, leadplant and other native plants usually show a remarkable recovery.
Leadplant is a member of the bean family (Fabaceae)
which contains hundreds of economically important plants. Fab means "bean" in
Latin. The generic name Amorpha stems from the Greek amorphos, "deformed," in
reference to the absence of four of the five petals normally found on
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