Culture
Grow in moist to wet loams in full sun to part shade. Best in part shade. Intolerant of dry soils. Best in a sheltered location protected from strong winds. Plants are dioecious (male and female flowers on separate plants) and should be grown in clumps to assure cross pollination will occur in the event fruiting on female plants is desired.
Noteworthy Characteristics
Napaea dioica, commonly called glade mallow, is a robust, coarse, dioecious, herbaceous perennial that typically grows to 4-8' tall. It is uncommon (listed by the CPC National Collection of Endangered Plants as "apparently secure", with the Holden Arboretum designated as primary custodian) throughout its midwestern U.S. growing range which extends from southeastern Minnesota and northeastern Iowa east to Wisconsin, northern Illinois, Indiana and Ohio. It was originally determined to be also native to Virginia and Pennsylvania, but some experts now believe this determination was based upon a misidentification of this species in those two states with a similar species (Sida hermaphrodita). It is native to moist thickets, floodplain forest openings, riverbanks, riverbottom prairies, ditches, alluvial meadows and lake margins.
Glade mallow has a single upright central stem. Small, fragrant, bractless, tubular white flowers bloom in cymose panicles in early to mid summer (June to early August) on outward branching side stems which appear on the upper half of the plant. Each flower (to 3/4" across) has a short tube which flares outward into 5 lobes. Flowers open in the morning and close up at night. Fruit is a schizocarp which appears in late summer on female plants and which splits open when ripe to disburse seeds (each schizocarp has 8-10 papery single-seeded mericarps). Leaves (to 10" long) with dentate margins have 5-9 palmate lobes. Largest leaves are found near the base of the plant. Notwithstanding its genus meaning and common name, this mallow is usually not found in glades.
Genus name from Greek means open woodland area or alpine glade.
Specific epithet from Greek means two houses in reference to the fact that plants are dioecious.
Problems
No serious insect or disease problems.
Uses
Best in moist part shade areas of the landscape.