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Cicerbita macrophylla

common blue-sow-thistle

Asteraceae Caucasus and southwestern Asia

Attracts Pollinators Attracts Butterflies

SunFull Sun – Part Shade

WaterMedium

HardinessZones 4–8

Overview

Cicerbita macrophylla is a tall, rhizomatous perennial of the daisy family, growing 2-6 feet (60-180 cm) tall and spreading by creeping underground stems into broad patches. The lower leaves are large, 8-12 inches (20-30 cm) long, lyre-shaped with a big triangular end lobe and smaller side lobes, on winged stalks; upper leaves are smaller and clasp the stem. The upper stem branches into a loose head of many flower heads, each about 0.8-1.2 inches (20-30 mm) across and made up of pale lilac-blue strap-shaped florets. Flowering is in mid- to late summer. Each head produces achenes with a white pappus carried on the wind. The plant dies back to the rhizomes in winter and regrows strongly in spring. It spreads quickly by rhizome fragments and seed and can form dense colonies that crowd out other plants.

Native Range

Native to the Caucasus and southwestern Asia, where it grows in damp mountain woodland and tall-herb meadows. Introduced as a garden plant elsewhere, it has naturalised widely in Britain and northwestern Europe along road verges, railway banks, riversides, and waste ground.

Suggested Uses

Sometimes grown in large wild gardens and tall-herb borders where its spread can be contained, spaced well apart in moist ground. It suits rough, naturalistic areas rather than small beds. Its rapid rhizome spread and free seeding make it unsuited to confined or mixed plantings.

How to Identify

Recognised by the tall stems, large lyre-shaped lower leaves with a big triangular end lobe, and the loose clusters of pale lilac-blue, strap-flowered heads about 0.8-1.2 inches (20-30 mm) across. The blue flower colour separates it from yellow-flowered sow-thistles and hawkweeds. Its creeping rhizomes and patch-forming habit distinguish it from clump-forming blue Cicerbita spp. relatives.

Appearance

Size & Dimensions

Height2' - 6'

Width/Spread2' - 4'

Colors

Flower Colors

Foliage Colors

Fall Foliage Colors

Bloom Information

Bloom Period

~6 weeks

Summer

Flowers from July to August, sometimes into early September. Each plant flowers over about 4-6 weeks, with heads opening in succession up the branched stem. Flowering is later in cool seasons and at the northern edge of its naturalised range. Heads close in dull weather and by afternoon.

Detailed Descriptions

Foliage Description

green

Growing Conditions

Sun Requirements

SunFull Sun SunPartial Shade

Requires 4-8 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 Range5.5 - 7.5(Neutral)

357912

Soil Types

loam clay silt

Drainagemoist

Water & Climate

Water Needs

Medium

Frost Tolerance

hardy

Time to Maturity

2-3 years

Care & Maintenance

Care Guide

Grows in partial shade to full sun on moist, fertile soils and tolerates a range of conditions, which underlies its spread. It needs no care to persist and increases quickly by rhizomes once established. Cutting the tops does not kill it, as it regrows from the root system; only removing the rhizomes checks it. Seed and rhizome fragments spread along watercourses and in dumped soil. It is treated as an invasive weed in parts of Britain and is recorded for control on some sites.

Pruning

Cut stems down before the seed heads ripen to limit wind-blown seeding. Cutting alone does not remove the plant, which regrows from rhizomes. Digging out the whole root system is the means of removal where spread is unwanted.