There are 15 species of Amorpha that are native to North America. They grow in dry prairies, scrub and sandy ground as well as woodlands and riverbanks. Amorpha’s native habitat ranges north and south from Canada to south Texas, New Mexico to Louisiana and Wyoming to Minnesota. They thrive in zones two to nine.
Amorpha canescens shrub has small, gray, aromatic leaves and tall racemes of small, dark violet flowers. It grows to about 3 feet tall. The common name is “lead plant” and one writer speculated that it was found growing on a lead mine and another said that its presence was thought to indicate where there was lead underground.
One seed source, Lorenz’s OK Seeds in Okeene, (580) 822-3655 and www.lorenzsokseedsllc.com, says it looks like it is covered in white lead.
The flowers bring bees and wasps for nectar. The caterpillars of Colias cesonia (Dogface Sulfur) and some moths eat the leaves. In turn, the insects feed the birds in our gardens. Deer and rabbits enjoy eating lead plants since it is a high protein pea.
Bowood Farms in St. Louis (www.bowoodfarms.com) offers the plant and they say it is cold hardy in zones five to eight. Bustani Plant Farm (www.bustaniplantfarm.com), where I bought my plant four years ago, rates its cold hardiness in zones four to nine. Owner Steve Owens said that another common name is Prairie Shoestrings because of its long deep stringy roots and 15-foot deep central root.
Prairie Moon (www.prairiemoon.com) commented that the tough roots made pioneer plowing difficult, causing early settlers to name it Devil’s Shoestrings. In Minnesota, it was called “Buffalo Bellow Plant” because it bloomed during bison rutting season (http://tinyurl.com/65864mu).
In traditional medicine, the leaves were made into tea to kill intestinal worms and treat eczema. Dried leaves are used to treat cuts and a tea made from the roots is used to ease stomach pain. The twigs are used to treat rheumatism.
The other Amorpha shrub that is a beauty in hot weather gardens is Amorpha fruticosa, known as False Indigo. It also has gray leaves though they are larger and more round. False Indigo will grow up to 10-feet tall over its lifetime. It also has purple flowers.
Its native range goes from coast to coast — most of the United States from Canada to Mexico.
False Indigo deer resistant and attracts butterflies. It can tolerate really wet soil followed by dry periods so is considered a good substitute for butterfly bush in a rain garden or dry creek. Rainscaping.org suggests it for erosion control, as well as boggy soils.
Several moth caterpillars use the plants’ leaves as food so they might be eaten to the stems over the summer.
Horizon herbs has the seeds available (www.horizonherbs.com) and Forest Farm (www.forestfarm.com) sells the plants.
To grow Amorpha from seed, start in the fall with pre-soaked seed in pots of light, well-drained soil. Amorphas are all members of the pea family so germination is increased with the use of legume (pea and bean) inoculant bacteria. They will take two months to come up.
These plants are best suited for naturalized gardens since they do not have tidy or compact growth habits. Lead plant only grows a few feet high but it can spread to 4 feet wide.
In our garden Amorpha is happy growing in the sun along a rock walkway.