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Lomatium triternatum

ternate desert-parsley

Apiaceae Western North America

Attracts Pollinators Attracts Butterflies Drought Tolerant

Native to North America

SunFull Sun

WaterLow · drought-tolerant

HardinessZones 4–8

Overview

Lomatium triternatum is a herbaceous perennial in the carrot family that grows from a deep, slender taproot and reaches 8–28 inches (20–70 cm) tall and 6–16 inches (15–40 cm) wide. Several erect stems rise each spring from the root crown and die back to the ground by midsummer. The leaves are divided ternately into long, narrow, linear segments 1.5–4 inches (4–10 cm) long, giving a grass-like outline. From April to June the stems carry compound umbels of small yellow flowers, each umbel 1.5–3 inches (4–8 cm) wide, held above the foliage on bare stalks. The flowers draw early-season bees and serve as a larval host for several swallowtail butterflies. Flat, winged, oblong fruits 0.3–0.5 inch (8–13 mm) long follow and split into two seeds at maturity. The taproot was a traditional food of Indigenous peoples of western North America. The plant grows on dry grasslands, sagebrush steppe, and open ponderosa pine slopes, going fully dormant by summer to survive seasonal drought. It resembles toxic relatives such as Cicuta spp. and Conium spp., which share the family's umbel form but differ in leaf shape and habitat.

Native Range

Native to western North America, from British Columbia south to California and east to Montana, Wyoming, and Colorado. It grows in sagebrush steppe, bunchgrass prairie, and open coniferous woodland on well-drained slopes.

Suggested Uses

Lomatium triternatum is used in native meadow restorations, sagebrush-steppe plantings, and rock gardens on dry sites. It supports early-season pollinators and serves as a larval host for swallowtail butterflies. The dormant summer habit suits plantings that receive no irrigation.

How to Identify

Identify Lomatium triternatum by its ternately divided leaves with long, narrow, linear segments 1.5–4 inches (4–10 cm) long and its yellow compound umbels held on leafless stalks in spring. Plants stand 8–28 inches (20–70 cm) tall and arise from a single deep taproot. The winged, flattened fruits set it apart from grasses, and its narrow leaf segments separate it from broader-leaved Lomatium spp. species.

Appearance

Size & Dimensions

Height8" - 2'4"

Width/Spread6" - 1'4"

Colors

Flower Colors

yellow

Foliage Colors

green

Fall Foliage Colors

no change

Bloom Information

Bloom Period

~5 weeks

Spring

Yellow umbels open from April to June, varying with elevation and latitude. Each plant flowers for roughly three to five weeks in spring before setting winged seed. Foliage and stems yellow and wither by midsummer as the plant enters dormancy.

Detailed Descriptions

Foliage Description

green

Growing Conditions

Sun Requirements

SunFull Sun

Requires 6-12 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 Range6.0 - 7.5(Neutral)

357912

Soil Types

loam sand rocky

Drainagewell drained

Water & Climate

Water Needs

Low

Frost Tolerance

hardy

Time to Maturity

2-4 years from seed to flowering

Drought Tolerance

Drought tolerant when established

Care & Maintenance

Care Guide

Lomatium triternatum grows in full sun on dry, well-drained soils including loam, gravel, and rocky substrates. It requires no supplemental water once established and depends on summer dormancy to survive seasonal drought. The deep taproot makes container culture and transplanting of mature plants difficult, so it is grown mainly from seed sown in autumn. Seed needs a period of cold, moist stratification to germinate. The plant declines in irrigated, fertile, or shaded sites and does not compete well with aggressive turf. Slugs and rot can affect plants kept too wet during summer dormancy.

Pruning

Lomatium triternatum needs no pruning. Spent flower stalks and foliage can be left to dry and self-sow, or cleared once the plant goes dormant in summer. Growth resumes from the root crown the following spring.