Mimulus ringens aka Allegheny Monkeyflower

Mimulus ringens is a North American perennial in the Phrymaceae family. Its common names include Allegheny monkey flower and square-stemmed monkey flower. Its native range spans central and eastern Canada and the United States. Wild plants grow in marshes, wet meadows, and low woods. They also grow beside streams and ponds. This upright plant spreads through creeping rhizomes and seed.

Garden plants often reach 1–3 feet [0.3–0.91 metres] tall. Some reach 4 feet [1.22 metres], beyond the usual range. Reported widths range from about 0.75–1.6 feet [0.23–0.5 metres]. The square stems have grooves along their sides. Branches often grow from the lower stems. Dark green leaves grow in opposite pairs without leaf stalks. Their blades are long and narrow, with toothed edges. The foliage has no hairs and dies back seasonally.

Flowers bloom from June to September, though local seasons vary. The blooms are often lilac or pale purple. Some plants have white flowers. Each tubular flower has two lips and an open mouth. Its shape recalls a snapdragon or a monkey's face. Long flower stalks rise from the upper leaf axils. Paired buds may open on separate days. Bumblebees pollinate the flowers, and butterflies visit the plants. Common buckeye and Baltimore checkerspot caterpillars also use this host. Oblong seed capsules follow the flowers. Each holds hundreds of seeds that wind can spread.

Grow this plant in fertile soil that stays moist or wet. It accepts full sun, but partial shade suits it best. It tolerates sand, loam, clay, and chalk soils. It also grows across acid, neutral, and alkaline conditions. Sources list USDA zones 3–8 and UK hardiness rating H4. Its need for steady moisture suits rain and bog gardens. Plant it near pond edges or in damp borders. Do not let border soil dry out.

This low-maintenance plant can form colonies where conditions suit it. Its flowers add colour to wet sites and native plantings. Deer resistance adds to its value in such spaces. Sources report few serious pest or disease problems. Still, slugs and snails may damage the plant. Powdery mildew can also occur. Cut back old growth when the season ends. Seed offers a means of propagation.