What hardiness zones is Romneya coulteri suitable for?

Romneya coulteri is suitable for USDA hardiness zones 7, 8, 9, 10.

What are the sun requirements for Romneya coulteri?

Romneya coulteri requires Full Sun.

How much water does Romneya coulteri need?

Romneya coulteri has Very Low water needs.

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Perennials

Romneya coulteri

Matilija poppy

Papaveraceae

Southern California (Los Angeles, San Diego, Riverside counties) and Baja California, Mexico; chaparral and dry canyon habitats

At a Glance

TypePerennial

HabitSpreading

FoliageSemi-evergreen

Height4-8 feet (1.2-2.4 m)

Width6-10 feet (1.8-3 m)

Growing Zones

USDA Hardiness Zones

7 - 10

Zone 7

Zone 8

Zone 9

Zone 10

These zones indicate the coldest temperatures this plant can typically survive.

Frost Tolerancehardy

Key Features

Attracts Pollinators

Deer Resistant

Drought Tolerant

Fragrant (light)

Native to North America

Maintenancelow

Overview

A large, spreading, semi-woody perennial subshrub in the family Papaveraceae, native to the chaparral, dry canyons, and coastal scrub of southern California and Baja California, Mexico. Plants establish slowly from the root but eventually form extensive spreading colonies 4–8 feet (1.2–2.4 m) tall and 6 feet (1.8 m) or more wide via deep, wide-spreading rhizomes. The deeply pinnately lobed, blue-gray to glaucous leaves 3–6 inches (8–15 cm) long are attractively textured and provide year-round structure in mild climates. From late May through July, the plant produces the largest flowers of any native North American perennial: bowl-shaped blooms 4–9 inches (10–23 cm) across with six to nine crinkled, papery white petals surrounding a prominent boss of golden-yellow stamens, resembling a fried egg — giving rise to the common nickname 'fried egg plant.' The flowers have a light, pleasant fragrance. Romneya coulteri is fiercely drought-tolerant once established but deeply intolerant of disturbance: it virtually cannot be transplanted after establishment, and spreading rhizomes are extremely difficult to contain or remove. Mildly toxic if ingested (alkaloids in foliage and sap).

Native Range

Native to the dry chaparral, rocky canyon slopes, and disturbed roadsides of southern California (Los Angeles, San Diego, Riverside counties) and Baja California, Mexico, growing in well-drained, often poor, rocky or sandy soil in full sun.

Suggested Uses

Planted as a bold specimen or massed in large-scale dry gardens, California native plantings, and naturalized slopes at 5–6 foot (1.5–1.8 m) spacing — allow full room for mature spread. The enormous white flowers and blue-gray foliage create a dramatic structural presence in summer. Combine with other drought-tolerant California natives (ceanothus, salvia, artemisia). Not appropriate for small gardens or areas where rhizome spread cannot be managed. Outstanding for erosion control on dry slopes.

How to Identify

Identified by large, spreading, semi-woody clumps of deeply pinnately lobed, blue-gray glaucous leaves and enormous bowl-shaped white flowers 4–9 inches (10–23 cm) across with crinkled papery petals surrounding a prominent central boss of golden stamens. The combination of enormous papery white flowers (the largest of any North American native perennial), blue-gray deeply lobed foliage, and spreading rhizomatous colonies in dry, sunny conditions is unmistakable.

Appearance

Size & Dimensions

Height4' - 8'

Width/Spread6' - 10'

Colors

Flower Colors

white

yellow

Foliage Colors

blue

gray

silver

Fall Foliage Colors

no change

Bloom Information

Bloom Period

~8 weeks

SpringSummer

Blooms late May through July in zones 7–10, with individual flowers lasting 2–4 days and new buds opening in succession over 4–6 weeks. The flowers are most productive during the first few years of establishment; mature colonies bloom abundantly. In the Pacific Northwest, plants that receive summer heat bloom reliably in June–July. The fragrant flowers are most effective as a bold summer display in naturalistic and dry garden settings.

Detailed Descriptions

Flower Description

pure white crinkled papery petals surrounding prominent golden-yellow stamens; bowl-shaped, 4–9 inches across; lightly fragrant

Foliage Description

blue-gray to glaucous; deeply pinnately lobed, 3–6 inches long

Growing Conditions

Sun Requirements

Full Sun

Requires 6-8 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 Range6.5 - 8.0(Alkaline)

357912

Soil Types

sandrockychalk

Drainage

well drained

Water & Climate

Water Needs

Very Low

Frost Tolerance

hardy

Time to Maturity

2-3 years

Drought Tolerance

Drought tolerant when established

Care & Maintenance

Care Guide

Plant in full sun in lean, sharply drained, sandy or rocky, neutral to slightly alkaline soil with a pH of 6.5–8.0. Once established, extremely drought-tolerant — summer watering should be minimal to none in dry-summer climates. Avoid amending soil with compost or fertilizer; lean, infertile conditions are preferred. Critical planting note: R. coulteri resents root disturbance profoundly — purchase small plants in containers and disturb the roots as little as possible when planting. Once established, the plant is nearly impossible to move or eradicate. The spreading rhizomes are aggressive — install a deep root barrier (18–24 inches / 45–60 cm) at planting if containment is needed. Hardy to zone 7 (0°F / -18°C) with good drainage.

Pruning

Cut all stems back to 6–12 inches (15–30 cm) above ground in late winter (February–March) before new growth begins — this annual hard cutback is essential and stimulates the most vigorous growth and flowering. Do not cut back in fall; winter stems provide some frost protection. Contain spread by cutting back rhizome runners at the perimeter with a sharp spade in early spring.

Pruning Schedule

early spring

Maintenance Level

low

⚠️ Toxicity Warning

Toxic to humans