Smooth Sow Thistle, Milk Thistle, Common Sow Thistle, Annual Sow Thistle, Hare's Colwort
Sonchus oleraceus

Family: Asteraceae (ass-ter-AY-see-ee) (Info)
Genus: Sonchus (SON-chus) (Info)
Species: oleraceus (awl-lur-RAY-see-us) (Info)

Category:

Annuals

Height:

18-24 in. (45-60 cm)

24-36 in. (60-90 cm)

Spacing:

24-36 in. (60-90 cm)

Hardiness:

USDA Zone 7a: to -17.7 C (0 F)

USDA Zone 7b: to -14.9 C (5 F)

USDA Zone 8a: to -12.2 C (10 F)

USDA Zone 8b: to -9.4 C (15 F)

USDA Zone 9a: to -6.6 C (20 F)

Sun Exposure:

Sun to Partial Shade

Danger:

N/A

Bloom Color:

Bright Yellow

Bloom Time:

Late Winter/Early Spring

Mid Spring

Late Spring/Early Summer

Mid Summer

Late Summer/Early Fall

Blooms repeatedly

Foliage:

Smooth-Textured

Veined

Other details:

May be a noxious weed or invasive

Drought-tolerant; suitable for xeriscaping

Soil pH requirements:

6.1 to 6.5 (mildly acidic)

6.6 to 7.5 (neutral)

7.6 to 7.8 (mildly alkaline)

Patent Information:

Non-patented

Propagation Methods:

From seed; direct sow outdoors in fall

Seed Collecting:

Allow seedheads to dry on plants; remove and collect seeds

Regional

This plant has been said to grow in the following regions:

Canoga Park, California

Austin, Texas

San Antonio, Texas

Leesburg, Virginia

Gardeners' Notes:

0
positives
1
neutral
0
negatives
RatingContent
Neutral

On Mar 6, 2008, htop from San Antonio, TX (Zone 8b) wrote:

Smooth sow thistle, milk thistle, swine thistle (Sonchus oleraceus) is an introduced plant from Europe that can be found growing natively in Texas and numerous other states. It can grow in just about any type of soil; however, it prefers nutrient rich soils. Smooth sow thistle has a considerable variation in leaf form and flower color.

This annual/biennial sow thistle forms a winter rosette, grows from a long taproot and is from 8 inches to 5 feet high. The stout stems are hollow, usually 5-angled, hairless and exude latex when broken. The spined leaves are grayish rather than dark glossy green like prickly sow thistle. However, both species can have some plants that fall in the intermediate range in this regard. In the shade, the leaves may have a have purple blotching... read more