Common name: Globe Thistle

Family: Asteraceae, Aster

Height x width: 3-4' x 2-3'

Growth rate: moderate

Foliage: alternate, 6-8" long, wavy and toothed with segments spiny (spinose) and thistle-like; upper surface rough, white hairy (setose) and greenish; lower surface white tomentose; basal leaves larger with petioles

Flowers: round globe heads 1½-2" across, dark to metallic blue; nice in bud even before flowers; long bloom for 6-8 weeks in summer with 4-8 flowers per branched stem (photo courtesy Missouri Botanical Garden plantfinder)

Hardiness: zones 3-8

Soil: well-drained, does well in dry and poor

Light: sun, tolerates part shade

Pests and problems: crown rot, aphids, four-lined plant bug (no problems serious)

Landscape habit, uses: borders, specimen, cut and dried fowers (cut just as flowers open for prolonged color retention), bees and nocturnal moths; plant low plants to cover base as basal leaves deteriorate

Other interest: name in Greek means "like a hedgehog" refering to the spiny flower bracts; native to Europe and Western Asia

Other culture: better color with cool nights but tolerates hot nights

Propagation: clump division (basal plantlets, minimum 3 year old plants) or root cuttings (2-3" long sections) in spring, seeds (2,600 per ounce) purchased as those collected often resulted in inferior seedlings


Of the 120 or so species, the following are the ones seen in commerce.

bannaticus (bah-nat-i-cuss')--similar to ritro only more hairy leaves, flower stems usually unbranched, and foliage is usually more deeply divided; native to southeast Europe

exaltatus (x-all-tah' tuss)--Russian Globe Thistle, more spiny leaves than ritro, unbranched stems, silvery white and later flowering inflorescences, tall to 8'; native to eastern Europe and western Russia

ritro (ree' tro)-- main species of commerce as described above; subsp. ruthenicus (rue-theh-ni-cuss')(ritro var. tenuifolius)--more deeply divided basal leaves with narrow segments than ritro, also shorter, white undersides of leaves, and less cold hardy

sphaerocephalus (sfair-o-cef' ah-lus)--2-6' tall, branched or unbranched, white or gray flowers, leaves white tomentose beneath; native to southern Europe to Russia

Cultivars: (considerable differences exist among sources as to correct species)
Cultivars species flowers height
'Blue Cloud' ritro soft blue, 2" across 3'
'Blue Globe' bannaticus dark blue 3'
'Blue Glow' bannaticus deep blue 3'
'Royal Blue' ritro metallic blue 2½'
'Taplow Blue' bannaticus metallic blue, 3" across 4-5'
'Taplow Purple' bannaticus violet blue 4-5'
'Veitch's Blue' ritro dark metallic blue 3-3½'

©Authored by Dr. Leonard Perry, Professor, University of Vermont as part of PSS123 course.

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