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perennial

Mountain Thistle

Acanthus montanus

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Mountain Thistle (Acanthus montanus) at Lakeshore Garden Centres

Mountain Thistle foliage

Mountain Thistle foliage

(Photo courtesy of NetPS Plant Finder)

Plant Height:  3 feet

Flower Height:  5 feet

Spread:  3 feet

Sunlight:  full sun  partial shade 

Hardiness Zone:  8a

Other Names:  Bear's Breeches, Alligator Plant

Description:

A shrubby perennial, featuring large, jagged spiny leaves of dark green, splashed with yellow-green variegation; impressive, bold spikes of pink to rose flowers tower over the foliage; longer leaves are more deeply cut than the species; a vigorous grower

Ornamental Features

Mountain Thistle features showy spikes of pink hooded flowers with rose overtones rising above the foliage in early summer. The flowers are excellent for cutting. Its attractive large deeply cut lobed leaves remain dark green in colour with showy chartreuse variegation and tinges of silver throughout the year.

Landscape Attributes

Mountain Thistle is an open herbaceous evergreen perennial with a rigidly upright and towering form. Its wonderfully bold, coarse texture can be very effective in a balanced garden composition.

This is a relatively low maintenance plant, and should be cut back in late fall in preparation for winter. Gardeners should be aware of the following characteristic(s) that may warrant special consideration;

  • Spreading
  • Suckering
  • Spiny

Mountain Thistle is recommended for the following landscape applications;

  • Accent
  • Mass Planting
  • General Garden Use
  • Naturalizing And Woodland Gardens
  • Container Planting

Planting & Growing

Mountain Thistle will grow to be about 3 feet tall at maturity extending to 5 feet tall with the flowers, with a spread of 3 feet. Its foliage tends to remain dense right to the ground, not requiring facer plants in front. It grows at a medium rate, and under ideal conditions can be expected to live for approximately 20 years. As an evegreen perennial, this plant will typically keep its form and foliage year-round.

This plant does best in full sun to partial shade. It does best in average to evenly moist conditions, but will not tolerate standing water. It is not particular as to soil type or pH. It is somewhat tolerant of urban pollution, and will benefit from being planted in a relatively sheltered location. Consider applying a thick mulch around the root zone in both summer and winter to conserve soil moisture and protect it in exposed locations or colder microclimates. This species is not originally from North America. It can be propagated by division.

Mountain Thistle is a fine choice for the garden, but it is also a good selection for planting in outdoor pots and containers. With its upright habit of growth, it is best suited for use as a 'thriller' in the 'spiller-thriller-filler' container combination; plant it near the center of the pot, surrounded by smaller plants and those that spill over the edges. It is even sizeable enough that it can be grown alone in a suitable container. Note that when growing plants in outdoor containers and baskets, they may require more frequent waterings than they would in the yard or garden. Be aware that in our climate, most plants cannot be expected to survive the winter if left in containers outdoors, and this plant is no exception. Contact our experts for more information on how to protect it over the winter months.

This plant is not reliably hardy in our region, and certain restrictions may apply; contact the store for more information.

 
 
Hardiness Zone Plant Height Minimum Sunlight
Characteristics
Accent  Massing  Garden  Naturalizing  Container 
Applications
Flowers  Foliage Color  Texture  Plant Form 
Ornamental Features