Sow Thistle
Sonchus oleraceus
A leafy annual resembling a soft thistle, with milky sap, lobed prickle-edged leaves and small dandelion-like yellow flowers. It is a widespread garden and field weed.
- Light
- Full sun to part shade
- Water
- Average
- Difficulty
- Easy
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Overview
Sow thistle (Sonchus oleraceus, common or annual sow thistle) is an annual weed in the aster family. Despite its name and prickly-looking leaves, it is not a true thistle and its spines are soft.
It grows quickly into a leafy, branching plant topped with clusters of small yellow flowers that resemble dandelions. Broken stems exude a milky latex. It is a familiar weed of gardens, fields and waste ground.
How to identify it
Recognize sow thistle by its soft-spined, lobed leaves, milky sap and small yellow flowers.
- Erect annual, often 1-4 ft tall, branching toward the top
- Deeply lobed leaves with soft, weakly prickly margins, often clasping the stem with rounded basal lobes
- Milky white sap that oozes from cut stems
- Clusters of small, yellow, dandelion-like flower heads
- Fluffy, parachute-like seeds dispersed by wind
Care & growing
Sow thistle is a weed; care details are for identification and control.
- Light: Full sun to partial shade
- Water: Average moisture; adaptable
- Soil: Tolerates most soils, favoring fertile, disturbed ground
- Temperature: Grows in cool to warm seasons; an annual or winter annual
- Propagation: By abundant wind-blown seed
- Control: Pull or hoe young plants before they flower and seed; mulch and dense planting suppress it. It pulls easily thanks to a relatively shallow taproot
Habitat & origin
Native to Europe, western Asia and North Africa, sow thistle has spread worldwide, including throughout North America.
It thrives in gardens, cultivated fields, vacant lots, roadsides and other disturbed, fertile, sunny sites. It is one of the most cosmopolitan weeds and readily colonizes bare soil.
Frequently asked questions
Is sow thistle a real thistle?
No. It is in the aster family and only loosely resembles a thistle; its leaf spines are soft rather than sharp, and it has milky sap like dandelions.
How do I control sow thistle?
Pull or hoe plants while young and before they flower, since they spread by wind-blown seed. They have a shallow taproot and come up easily, and mulch helps prevent new seedlings.
How can I identify sow thistle?
Look for an erect annual 1-4 ft tall with deeply lobed, soft-prickled leaves that clasp the stem, milky sap from cut stems, and small yellow dandelion-like flower heads.
How does sow thistle spread?
It reproduces entirely by abundant fluffy, parachute-like seeds carried on the wind, allowing it to colonize bare and disturbed soil quickly.
Sow Thistle guides
In-depth guides for identifying, growing, and caring for Sow Thistle.
