Cirsium Species, Roadside Thistle, Tall Thistle

Cirsiumaltissimum

Family
Asteraceae (ass-ter-AY-see-ee)
Genus
Cirsium (SIR-see-um)
Species
altissimum (al-TISS-ih-mum)
Synonym
Carduus altissimus
Cirsium diversifolium
Sun Exposure
Full Sun
Foliage
Herbaceous
This plant is resistant to deer
Height
36-48 in. (90-120 cm)
4-6 ft. (1.2-1.8 m)
6-8 ft. (1.8-2.4 m)
Spacing
36-48 in. (90-120 cm)
Hardiness
USDA Zone 4a: to -34.4 °C (-30 °F)
USDA Zone 4b: to -31.6 °C (-25 °F)
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)
USDA Zone 10a: to -1.1 °C (30 °F)
USDA Zone 10b: to 1.7 °C (35 °F)
Danger
Plant has spines or sharp edges; use extreme caution when handling
Bloom Color
Lavender
Bloom Time
Late Summer/Early Fall
Mid Fall
Other Details
Category
Biennials
Perennials
Water Requirements
Drought-tolerant; suitable for xeriscaping
Average Water Needs; Water regularly; do not overwater
Foliage Color
Where to Grow
Bloom Characteristics
This plant is attractive to bees, butterflies and/or birds
Bloom Size
Other details
May be a noxious weed or invasive
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
Propagation Methods
From seed; direct sow outdoors in fall
From seed; winter sow in vented containers, coldframe or unheated greenhouse
From seed; sow indoors before last frost
Self-sows freely; deadhead if you do not want volunteer seedlings next season
Seed Collecting
Allow seedheads to dry on plants; remove and collect seeds
Properly cleaned, seed can be successfully stored
Regional

This plant is said to grow outdoors in the following regions:

Cole Camp, Missouri

Guysville, Ohio

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Gardener's Notes:

0
positive
0
neutral
0
negative
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