Senecio vulgaris
Senecio vulgaris
Common Groundsel
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Taxonomy
Family Asteraceae · Genus Senecio
Description
Senecio vulgaris, known as common groundsel, is a quick-growing annual with small yellow tufted flowers and fluffy seed heads. It thrives in poor, disturbed soils and often pops up uninvited. While easy to grow, it self-seeds aggressively and is toxic if eaten, so manage carefully around pets, livestock, and veggie beds.
Common Names
Common GroundselGroundselOld-man-in-the-springSimson’s Groundsel
Context
nativeRegion
Native to Europe, North Africa, and temperate Asia; now naturalized worldwide.
usdaZones
Annual/weed across USDA 2-11.
companionPlants
None (generally not recommended), Cabbage (aphid trap crop), Broccoli (aphid trap crop), Kale (aphid trap crop)
culturalUses
Historically used in folk remedies, but modern internal use is discouraged due to hepatotoxic pyrrolizidine alkaloids; noted as a toxic weed to livestock.
Care
Care Requirements
LightFull sun to partial shade; flowers best with 4–8 hours of direct light.
WateringModerate. Keep soil lightly moist; tolerates short dry spells but avoid waterlogging.
SoilAny well-drained soil, including poor and disturbed sites; pH roughly 5.5–7.5.
FertilizerNot needed; extra nutrients only encourage faster spread.
HumidityAdaptable; average ambient humidity is fine.
TemperatureGerminates at 40–77°F (5–25°C); grows best at 50–70°F (10–21°C); tolerates light frost.
Growth & Life Cycle
HabitHerbaceous annual; often behaves as a winter annual in cool climates; upright, branching.
Mature Size4–18 in tall (10–45 cm) and 4–12 in wide (10–30 cm).
Growth RateFast; can go from seed to flower in 5–7 weeks.
BloomingSmall yellow disc florets; blooms most of the year in mild climates, mainly spring to fall.
DormancyNo true dormancy; plants die after seeding, but a persistent seed bank maintains populations.
Propagation
MethodsSeed (self-seeding), Broadcast sowing
DifficultyVery easy
Best SeasonFall or early spring, when soils are cool and moist.
Maintenance & Notes
PruningHand-pull or cut before flowering/seed set; bag and dispose to prevent spread.
RepottingNot typically container-grown; if in pots, refresh soil annually and remove volunteers promptly.
Pests & DiseasesCan host aphids, whiteflies, and leaf miners; susceptible to groundsel rust (Puccinia lagenophorae), powdery mildew, and damping-off.
ToxicityToxic to humans, pets, and livestock if ingested due to pyrrolizidine alkaloids; may cause liver damage. Avoid ingestion and handle with care.
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