Stipa

These deciduous or evergreen grasses are a favourite of garden designers, says Miranda Kimberley.

Stipa calamagrosti - image: Floramedia
Stipa calamagrosti - image: Floramedia

Stipa is a "must have" for many garden designers. When a low grass is called for, S. tenuissima is drafted in with its feathery heads, adding a lovely texture as they undulate in the wind. Alternatively, S. gigantea Award of Garden Merit (AGM), with its large, golden, oat-like flower heads, is often the choice when a tall grass is required. But there are also several other design-worthy species.

Stipa is a huge genus of around 300 species. They can be deciduous or evergreen grasses and their natural habitat is open woodlands, stony slopes and steppes. They originate from temperate and warm-temperate regions in New Zealand, Europe, Asia and the Americas.

The genus has become more difficult to pin down after being reclassified. Many species have been renamed but continue to be referred to as Stipa in the trade.

As well as the two favourites, there is the excellent S. calamagrostis, which will also appear under its synonym Achnatherum calamagrostis. It forms quite a large clump and produces lots of fluffy silvery-white flower heads in late summer.

S. arundinacea, generally now referred to as Anemanthele lessoniana AGM, has the common name pheasant's tail grass because its evergreen foliage takes on tints of copper, gold and bronze in the autumn and its hazy pink trailing flower heads are a feature, too.

Garden-worthy Stipa are happy in well-drained soil in a sunny position. In the border, Stipa, particularly gigantea, do not like to be crowded, mimicking how they grow on open sites in their native habitat. They will roll up their leaves in drought conditions while they do not cope well at all with having their roots wet in winter.

Plants in containers should be looked after carefully and not allowed to stand in full drip trays. They are best grown from seed, which should be sown in the autumn so plants are exposed to frost. They tend to be slow to establish if divided.

Outside of ornamental horticulture, Stipa is a useful economic plant. S. tenacissima, or esparto grass, is grown in north-west Africa and its fibres are used to weave bags and the once again trendy espadrille. The fibres are also used to make high-quality paper as well as thin paper for rolling cigarettes.

What the specialists say

- Hayley Willerton, partner, the Alpine & Grass Nursery, Spalding, Lincolnshire

"The genus is very popular, with certain forms having particular beauty with their ability to dance in the wind and hold the light. Mostly perennial and non-invasive, they are also popular to wildlife, such as the nest-building material provided by S. tenuissima (Mexican feather grass).

"My favourite is S. arundinacea, with its beautiful leaf colour that changes throughout the year. The tallest evergreen grass, it is hardy, versatile and looks good in drifts or even in patio containers.

"Its seed heads are also attractive to finches during autumn. Last year, we supplied a local theatre restaurant with just this grass for its long lengths of raised planters. They looked fantastic throughout the summer.

"Stipa generally prefer well-drained soil in sun. The main thing to avoid is too much winter wet. If in containers, make sure that they are never standing in water."

- Neil Lucas, owner, Knoll Gardens, Dorset

"Stipa are first-rate garden plants. Easy movement and long-lasting appeal can be claimed for most grasses. Stipa have these qualities in abundance. It's a very large group so you need to choose ones that work best for your particular situation.

"A few years ago, the family was split into smaller sections. S. tenuissima became Nassella tenuissima and is still one of the most widely grown of all grasses, and deservedly so. My favourite is probably S. gigantea because it is quite magnificent when in full plume and can bring drama and effect to even quite small plantings.

"They are easy to grow in mostly sunny, well-drained to droughty conditions. They prove effective pretty quickly, making us want to reach out and touch them. Some, like N. tenuissima, need dividing every few years to keep them fresh, whereas S. gigantea is best left undisturbed to build up the energy it needs for its magnificent displays."

In practice

- Shelley Mosco, managing director, Green Graphite Landscape Design, London

"I tend to only use S. gigantea and S. tenuissima - gigantea to look at all year round and tenuissima to pet. I like to use gigantea for large specimen planting. As it's generally evergreen, it always has a presence.

"I like to match it up with tall, wiry plants with umbel flowers or spires - something like Veronicastrum virginicum or Verbena bonariensis AGM.

"Tenuissima, with its smaller scale, is best planted in big slices on banks or borders. It's excellent for somewhere like a sensory garden because of its soft, tactile nature. While both are easy to establish, be aware that gigantea does not like to be crowded. Give them plenty of room."

Species and varieties

- S. arundinacea, renamed Anemanthele lessoniana AGM (H4), produces arching clumps of evergreen foliage, tinted copper, gold and bronze in autumn through to spring and hazy pink trailing flower heads. Evergreen - comb out dead foliage in the spring. Height: 1m. Spread: 1.2m.

- S. barbata forms tidy clumps of green foliage with long, slender, silvery flower heads. Can be difficult to establish. Dislikes competition and likes a sunny, well-drained spot. Height: 60-80cm. Deciduous.

- S. calamagrostis (syn. Achnatherum calamagrostis) is a fantastic species that produces long, slender, arching leaves and masses of long, fluffy, silvery-white flowers in late summer. The whole clump matures to a buff colour in the autumn. Deciduous - cut down to the ground in late winter. Height: 1m. Spread: 1.2m.

- S. elegantissima (syn. Austrostipa elegantissima) is best grown in a pot with some winter protection. It produces airy flower panicles throughout the season that dry to an attractive silver/beige colour. Prefers extremely well-drained soil. Semi-evergreen. Height: up to 40cm.

- S. gigantea AGM (H4), or golden oats, forms a dense clump of arching grey-green foliage from which long-stemmed, oat-like flower heads emerge in midsummer. These bend over as they mature. Makes a good architectural feature when outlined in frost. Height: 1.8m. Evergreen.

- S. gigantea 'Gold Fontaene' is a lovely selection made by German nurseryman Ernst Pagels. It produces huge clumps of narrow foliage and spikes of large golden-brown upright flower heads. These are held high above the foliage and last well into the winter. Needs a sunny well-drained spot. Height: 2-2.4m. Evergreen.

- S. grandis forms basal clumps of narrow foliage that are topped by cat whisker-like flowers that colour buff as the season progresses. Likes a sunny, well-drained position. Height: 70-90cm. Deciduous.

- S. ramosissima (syn. Austrostipa ramosissima) is lovely but may need some winter protection. Forms clumps of dense, strongly upright stems producing a mass of airy inflorescences over a long period. Semi evergreen. Height: 1.8-2.2m.

- S. tenuissima (syn. Nasella tenuissima) is widely used by garden designers because it forms neat clumps and has elegant feathery seed heads that move in the wind. Good for specimen or mass plantings, and good in containers as well. Likes a well-drained sunny spot. Height: 60cm. Spread: 30cm. Evergreen.

Thank you to Floramedia, which supplied the images for this article from its photo library

www.floramedia-picture-library.com


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