From fertile floodplains to heavy Saint Louis clay to the Ozark's thin, rocky topping, the heartland state of Missouri has soils as varied as its seasons. Stormy, tornado-prone springs; hot, humid summers; temperamental autumns and frigid winters combine with these soils to test every gardener's skills. The Missouri Botanical Garden helps by identifying native plants which are tolerant of growing conditions in each region of the Show-Me State.
Lead plant (Amorpha canescens), a small shrub of the pea family, grows wild in Missouri's open woodlands and on its river bluffs and prairies. Standing from 1 to 3 feet high, with a spread of 2 to 2.5 feet, lead plant has feathery gray-green leaves. Spikes of single-petaled blue or purple flowers, according to the Missouri Botanical Garden Bloom Data Sheet, appear from June until as late as September. Butterflies feed on the nectar.
Lead plant is common on Missouri's prairies and in open woodlands. Under cultivation, it works best in wildflower gardens or meadows. Plant disease-and-pest-resistant lead plant in sun and dry, well-drained sandy or rocky soil. It naturalizes easily.
A perennial of the milkweed family, swamp milkweed (Asclepias incarnata) thrives in Missouri's wet prairies, swamps and bogs. Occasionally reaching 5 feet, it typically standing 3 to 4 feet high with a 2-to-3-foot spread.
Swamp milkweed puts on a show any time between June and September, depending on seasonal growing conditions. Its tall stems bear rounded clusters of pink to mauve flowers above medium-green lance-shaped leaves. Attractive 4-inch brown seedpods stay on the plants through the winter, releasing their seeds on silken threads in the early spring.
This clumping herb is a great choice for sunny spots with moist to wet soils. Few plants do as well as swamp milkweed in the wet clay soils common around Saint Louis. Swamp milkweed's biggest drawback is its susceptibility to aphids. Periodic spraying with soap and water solution discourages them. Consider this plant for water or butterfly gardens.
Purple Polly Mallow
A Missouri Botanical Garden Plant of Merit, purple poppy mallow (Callirhoe involucrata) has bloomed from May to September in some years. A perennial ground cover standing up to 1 foot high and 3 feet wide, purple poppy mallow grows wild in Missouri's dry, rocky prairie soils. It often brightens the state's northeastern roadsides. Cup-shaped, magenta five-petaled flowers, says the Lady Bird Johnson Wildflower Center, account for the plant's other common name " winecup."
While the plants' deep tap roots protect them from drought, they also make transplanting difficult. Fortunately, the plants self-sow easily, forming ground covers fairly quickly. They're also effective when they are trained to cascade over stone walls. Plant them in full sun in well-drained, dry acidic soil--they handle every soil from sandy to clay but won't tolerate poor drainage.