Plant of the Month for September, 2013

 (berk-HE-yuh pur-PUR-ee-uh)

General Information:

A thistle you can actually love and best of all, your friends will be extremely envious of your prized possession. Berkheya purpurea (purple berkheya) is one of those rare plants from Africa that seems to do quite well in gardens including cold northern gardens. Many sources on the net report a hardiness of only 6 or 8, but there are plants that have overwintered north of Toronto, and in my Ontario zone 5 garden. For northern gardeners the plant is certainly worth another look.

Berkheya purpurea; photo by Robert Pavlis

B. purpurea is a prickly thistle. It forms a low rosette at ground level, and then in June a flower stock starts to grow. It flowers at 1 m high in early August with flowers that are 8-10 cm in size. Flowers open in succession from the top of the stem downwards, unlike most plants that open flowers from the bottom, up. Each flower lasts a few days and a single plant can have up to 15 flowers (5-8 is normal).

Berkheya purpurea; photo by Robert Pavlis

The plant is reported to have a taproot, but it is also described as rhizomatous.  It is possible that a young plant has a tap root that branches out as the plant matures into a multi-headed clump.  It is fast growing, long lived and has few pests, especially the 4 legged kind – it is just too prickly to eat. When you plant it in the garden, mark it well so that no-one weeds it out by mistake.

Purple berkheya is the only mauve to purple flowered species in the genus; most of the others are yellow or in some cases white.

Life Cycle: perennial

Height: 5 cm (2 inches), flowers at 1 M (3 ft)

Bloom Time: mid to late summer

Natural Range: South Africa (1,500 – 3,000m)

Habitat: moist, steep, grassy mountain slopes

Synonyms:  Stobaea purpurea, Crocodilodes purpureum

 

Cultivation:

Light: full sun

Soil: good drainage

Water: average moisture to dry

USDA Hardiness Zone: 5?– 11

Propagation: seed, division

Seedex availability (ORG&HPS annual Seed Exchange): usually

A

Sow @ 20°C. Seed germinates within 3 months.
Berkheya purpurea GRRA 2014
Robert Pavlis