Silphium Species, Slender Rosinweed

Silphium radula var. gracile

Family: Asteraceae (ass-ter-AY-see-ee) (Info)
Genus: Silphium (SIL-phee-um) (Info)
Species: radula var. gracile
Synonym:Silphium gracile



Foliage Color:

Unknown - Tell us

Bloom Characteristics:

This plant is attractive to bees, butterflies and/or birds

Water Requirements:

Average Water Needs; Water regularly; do not overwater

Where to Grow:

Unknown - Tell us


4-6 ft. (1.2-1.8 m)


12-15 in. (30-38 cm)

15-18 in. (38-45 cm)

18-24 in. (45-60 cm)


USDA Zone 5a: to -28.8 C (-20 F)

USDA Zone 5b: to -26.1 C (-15 F)

USDA Zone 6a: to -23.3 C (-10 F)

USDA Zone 6b: to -20.5 C (-5 F)

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)

USDA Zone 9b: to -3.8 C (25 F)

Sun Exposure:

Full Sun

Sun to Partial Shade


Unknown - Tell us

Bloom Color:

Bright Yellow

Bloom Time:

Late Summer/Early Fall

Mid Fall



Other details:

Unknown - Tell us

Soil pH requirements:

5.6 to 6.0 (acidic)

6.1 to 6.5 (mildly acidic)

6.6 to 7.5 (neutral)

Patent Information:

Unknown - Tell us

Propagation Methods:

By dividing the rootball

From seed; direct sow outdoors in fall

Seed Collecting:

Allow seedheads to dry on plants; remove and collect seeds

Properly cleaned, seed can be successfully stored


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

Dripping Springs, Texas

Houston, Texas

Gardeners' Notes:


On Sep 4, 2016, marasri from Dripping Springs, TX wrote:

Maybe mine has hybridized with other Silphiums because it is 6' tall and growing in alkaline soul. I do like whatever it is because it grows without human assistance of any kind, and blooms for a long time. Never needs watering. It can take some partial shade. Unfortunately the live oak has expanded and it is a leaning live oak so the flowers are in the low branches.


On Aug 27, 2006, dmj1218 from west Houston, TX (Zone 9a) wrote:

This plant is native to the prairies, long-leaf pine savannahs, and roadsides in southeast Texas to Aransas county and east into Louisiana and is rarely found anymore in Texas in its pure form. This is because it's genetic integrity is comprimized due to the fact that it hybridizes easily with the taller, more aggressive native Silphiums such as S. laciniatum (compass plant), S. albiflorum (white rosinweed), and S. radula (roughstem rosinweed).

Slender rosinweed is usually about knee-high and is a well behaved garden plant prefering acidic sandy to sandy loam soils that are well-drained. The 2-3" blooms are a large translucently clear yellow. The plant colonizes by rhizomes and is easily grown from seed or by dividing the rootball while dormant in winter.