Senecio vulgaris, common groundsel
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Herbaceous

Senecio vulgaris

common groundsel

AsteraceaeEurope, western Asia

At a Glance

TypeAnnual
HabitUpright
FoliageDeciduous
Height4-18 inches (10-45 cm)
Width4-10 inches (10-25 cm)

Key Features

Deer Resistant
Maintenancemoderate

Overview

Senecio vulgaris is a low-growing, erect annual in the daisy family (Asteraceae) reaching 4–18 inches (10–45 cm) tall with a 4–10 inch (10–25 cm) spread. Stems are erect, branching, smooth to sparsely hairy, somewhat fleshy. Leaves are alternate, pinnately lobed with irregularly toothed segments, 1–4 inches (2.5–10 cm) long, clasping the stem at the base, smooth to sparsely hairy, somewhat fleshy. Flower heads are small, cylindrical, 0.3–0.4 inch (8–10 mm) long, with yellow disc florets only — completely rayless (no ray florets). Phyllaries have conspicuous black tips, a diagnostic feature shared with S. sylvaticus. Fruit is an achene with a white pappus, forming a small dandelion-like sphere at maturity. A single plant produces 1,000–15,000 seeds, dispersed by wind. The life cycle completes in 5–6 weeks, with multiple overlapping generations per year. In the Pacific Northwest, flowering and seed production occur nearly year-round. Contains pyrrolizidine alkaloids; toxic to livestock and humans. One of the most common garden weeds in the Pacific Northwest, appearing in cultivated beds, nursery containers, and disturbed ground year-round.

Native Range

Native to Europe and western Asia, occurring in gardens, nurseries, cultivated fields, and disturbed ground from sea level to approximately 8,000 feet (2,400 m). Naturalized across all 50 U.S. states and all Canadian provinces. One of the most common garden weeds worldwide.

Suggested Uses

Used in Asteraceae identification for the rayless head comparison: S. vulgaris (rayless) versus S. sylvaticus (short curled-back rays) versus Jacobaea vulgaris (prominently spreading rays). The black-tipped phyllaries are a standard Senecio diagnostic feature. The rapid life cycle and year-round germination are primary teaching examples in weed reproductive biology. The pyrrolizidine alkaloid content is taught in livestock and human toxicology alongside Jacobaea vulgaris and S. sylvaticus.

How to Identify

Distinguished from Senecio sylvaticus (wood groundsel) by the completely rayless flower heads (versus short curled-back rays), the shorter stature, the non-glandular (versus glandular-sticky) stems, and the preference for gardens and cultivated ground (versus disturbed forest sites). Distinguished from Jacobaea vulgaris (tansy ragwort) by the rayless heads (versus prominently rayed), the annual habit (versus biennial/perennial), and the much smaller size. The cylindrical rayless heads with black-tipped phyllaries, the fleshy pinnately lobed leaves, and the year-round presence are diagnostic.

Appearance

Size & Dimensions

Height4" - 1'6"
Width/Spread4" - 10"

Colors

Flower Colors

yellow

Foliage Colors

green

Fall Foliage Colors

no change

Bloom Information

Bloom Period

~40 weeks
J
F
M
A
M
J
J
A
S
O
N
D
SpringSummerFallWinter
Flowers nearly year-round in the Pacific Northwest, completing multiple generations annually. Individual plants complete their life cycle in 5–6 weeks from germination to seed dispersal. The white pappus spheres are visible at any time of year. Self-pollinating. Seeds germinate at soil temperatures as low as 40°F (4°C).

Detailed Descriptions

Flower Description

Yellow

Foliage Description

Medium green, pinnately lobed with irregularly toothed segments; smooth to sparsely hairy, somewhat fleshy

Growing Conditions

Sun Requirements

Full Sun
Partial Shade
Requires 4-10 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
loamsandsiltclay
Drainage
well drained

Water & Climate

Water Needs

Medium

Frost Tolerance

hardy

Care & Maintenance

Care Guide

Hand-pulling before seed set is effective; the shallow, fibrous root system extracts easily. The rapid life cycle (5–6 weeks) means pulling must occur before the white pappus appears, as seeds disperse immediately. In garden beds, hoeing at weekly intervals during the growing season prevents seed set. Mulching with 2–3 inches (5–8 cm) of organic material suppresses germination. In nursery settings, sanitation of container surfaces and growing media reduces spread. The year-round germination and rapid cycling mean the species is present in gardens in every season in the Pacific Northwest.

Pruning

No pruning applicable. Plants are pulled or hoed before the white pappus appears. The rapid 5–6 week life cycle requires frequent monitoring, particularly in spring and fall when germination rates peak.

Maintenance Level

moderate

⚠️ Toxicity Warning

Toxic to pets and humans
Senecio vulgaris (common groundsel) - Identification & Care Guide | PlantRef