The genus Pennisetum comprises about 80 species, mostly perennial, from sub-tropical and warm temperate regions of the world. Many are highly ornamental, and for the most part, clump-forming (a few are rhizomatous), with neat tussocks of arching foliage from which numerous fountains of plume-like inflorescences emerge from mid- to late summer. The seedheads persist throughout the winter and the sere foliage can be an asset during the colder months when brown becomes more valuable in the garden.
With so many pennisetums now on offer, we can fully recognise their terrific garden potential. When planting Pennisetum, consider how to bring out the best of the plant, either by planting in drifts, or, if your chosen species or cultivar is bold enough, leaving it to stand on its own. The lovely flowers and foliage combine well with late-summer perennials, such as asters or Helianthus.
I first became aware of the attractions of Pennisetum during my student days at Kew. Adjacent to the School of Horticulture is the Grass Garden, a wonderful oasis with a central patch of lawn that became a bolthole for students looking to relax between lessons. From this spot you could observe how visitors, particularly children, were drawn to the fountain grasses when in flower, stroking the long, bristly plumes as they would the tail of a cat.
The shorter species are particularly well suited for the front of the border. The foliage remains smart from head to toe and acts as a useful screen when placed in front of taller perennials, such as phlox, the lower leaves of which often become ragged as the season progresses. The fine foliage and soft, arching flowerheads sway in the slightest breeze and this attribute is highlighted when planted next to a stiff shrub.
It is well worth seeking out Knoll Gardens, Dove Cottage Nursery and Garden, or the Grass Garden at Kew for inspiration on using grasses in the garden. Below you’ll find some of the best Pennisetum’s to grow, chosen by head gardener Matthew Reese.
The best Pennisetum for late summer borders
Pennisetum orientale ‘Tall Tails’
Taller and more imposing than the type species, this plant can be used as a focal point or en masse in a border, or planted in a pot. It produces long, buff, catkin-like plumes with a hint of pink in late summer. Loose habit.
Height 1.4m. Hardiness rating USDA 5a-8b.
Pennisetum ‘Fairy Tails’
A hybrid with an upright habit that flowers from early summer onwards. Copious, airy, bottlebrush flowers of faded-pink age to gold-grey. Leave for winter effect and tidy in the spring.
Height 90cm. Hardiness rating RHS H3.
Pennisetum orientale ‘Karley Rose’
A superb plant that produces masses of silvery-pink flower spikes from July into autumn above a dense tussock of arching green leaves. Works well as a specimen or in groups. Suitable for cooler areas.
Height 60cm. Hardiness rating RHS H3, USDA 5a-8b.
Pennisetum thunbergii ‘Red Buttons’
Hailing from the African savanna, this delicate, clump-forming species produces masses of small, dense flower spikes atop willowy stems. The flowers age to pale brown. Needs sharp drainage and a sheltered spot. Tidy in the spring.
Height 1m. Hardiness rating RHS H3.
Initially makes an upright plant topped with silvery-green flowerheads. As the season progresses, the flowers age to brown and set seed, and the stems splay. It has a mild running habit and needs a sheltered position if grown in colder regions.
This reliable, vigorous cultivar produces mounds of arching, blue-green foliage and pink, bristly flower spikes from July into autumn. Plant in full sun with good drainage. Cut the flower spikes for flower arrangements before they set seed.
Height 1.2m. Hardiness rating RHS H3.
Pennisetum alopecuroides ‘Cassian’s Choice’
Named for the German horticulturist, Cassian Schmidt, this cultivar has bristly, dark flower spikes from August above mounds of fresh-green foliage. It will continue throughout autumn and well into winter.
Height 1m. Hardiness rating USDA 5a-9b.
Pennisetum x advena ‘Rubrum’
Best treated as a tender perennial, this cultivar has purple-red foliage and long, drooping flower spikes to match. Prefers rich, moist soil and is suitable for borders or pots. Lift in autumn and protect from frost. Plant out in late May.
Height 1.6m. Hardiness rating RHS H3.
Pennisetum alopecuroides ‘Dark Desire’
Red, whiskered flowers, above mounds of lush, dark foliage, darken with age. It looks sublime backlit in low autumn sunlight and prefers a sunny spot in good soil that doesn’t sit wet in winter. Selected by Knoll Gardens.
One of the finest grasses for the front of the border, if a little messy. Arching stems bearing fluffy, silver flower spikes are produced from mid-August and persist into autumn. Plant in a hot, dry site, and only cut back in the spring. Good for flower arranging.
Height 60cm. Hardiness rating RHS H3.
Pennisetum alopecuroides ‘Black Beauty’
A striking, dark-flowered form, with long, cylindrical plumes that look wonderful backlit by the evening sun. It favours a moist, free-draining soil that is not too dry. Performs best in southern English counties in a warm, sheltered position.
An attractive, vigorous spreader, ideally confined to a container. If grown in the border, monitor it closely and use a root barrier to check its progress. This cultivar produces greenish-white flowers throughout the summer that fade to tan-brown with age.
Pennisetum alopecuroides ‘Hameln’
A compact form that produces masses of curved, silver-green flower spikes atop arching, green foliage. It develops gold hues in autumn and will remain attractive through the winter. Remove old foliage in spring.