Ptilimnium spp.

mock bishopweed

Apiaceae North America

Attracts Pollinators Attracts Butterflies Container Friendly

Native to North America

SunFull Sun – Part Shade

WaterHigh

HardinessZones 5–9

Overview

Ptilimnium spp. is a small genus of annual to short-lived perennial herbs in the carrot family (Apiaceae), native to North America. Plants are slender and upright, typically 8-36 inches (20-90 cm) tall, with hollow, branching stems. The leaves are finely divided into thread-like (filiform) segments, so the foliage looks feathery or almost leafless, and in some species the divisions are arranged in whorls. From late spring through autumn the stems carry flat-topped compound umbels of tiny white flowers, much like a smaller wild relative of Daucus spp. (Queen Anne's lace). The flowers draw small bees, flies, wasps, and other insects, and are followed by small ribbed fruits. Most species grow in wet ground, including marshes, swamps, ditches, pond margins, and seasonally flooded flats, and several occur in coastal and tidal wetlands. P. nodosum is federally listed as endangered in the United States. The genus tolerates wet, poorly drained soils that many garden plants cannot, but it is short-lived and depends on reseeding to persist.

Native Range

Ptilimnium spp. is native to North America, mainly the eastern, central, and southern United States. Species grow in freshwater and brackish wetlands, marshes, wet prairies, ditches, and the margins of ponds and streams, including tidal areas along the coast.

Suggested Uses

Grown in rain gardens, bog gardens, pond and stream margins, and wetland and native plantings. The feathery foliage and white umbels suit naturalistic and pollinator-focused wet areas. Species are also used in wetland restoration and stormwater plantings.

How to Identify

Recognize Ptilimnium spp. by its thread-like, finely divided foliage and its flat-topped compound umbels of tiny white flowers on slender, branching stems. The feathery leaves and small umbels distinguish it from larger members of the carrot family. It is almost always found in wet ground.

Appearance

Size & Dimensions

Height8" - 3'

Width/Spread6" - 1'6"

Reaches mature size in approximately 1 years

Colors

Flower Colors

white

Foliage Colors

green

Fall Foliage Colors

no change

Bloom Information

Bloom Period

~16 weeks

Spring Summer Fall

Flowering runs from late spring through autumn, often May to October, with the long season typical of the genus. The small white umbels open in succession over many weeks. Ribbed fruits follow and shed seed into the surrounding wet soil.

Detailed Descriptions

Foliage Description

green

Growing Conditions

Sun Requirements

SunFull Sun SunPartial Shade

Requires 6-10 hours of direct sunlight daily

• Full Sun: 6+ hours of direct sunlight

• Partial Shade: 3-6 hours of direct sunlight

• Full Shade: Less than 3 hours of direct sunlight

Soil Requirements

pH Range5.5 - 7.5(Neutral)

357912

Soil Types

loam clay silt

Drainagewet

Water & Climate

Water Needs

High

Time to Maturity

1 year

Care & Maintenance

Care Guide

Grow Ptilimnium spp. in full sun in consistently moist to wet soil, including the margins of ponds, bog gardens, and rain gardens. The genus tolerates standing water, poor drainage, and both freshwater and brackish conditions that suit few other ornamentals. Keep the soil wet, as plants decline quickly if allowed to dry out. Little feeding is needed in reasonable soil. Because most species are annual or short-lived, allowing some plants to set and drop seed maintains the planting. Plants are easily raised from seed sown on damp ground.

Pruning

Ptilimnium spp. needs little or no pruning. Spent stems can be cut back after seeding to tidy the planting, though leaving some seed heads sustains self-sowing. Old growth dies back and can be cleared at the end of the season.