• AGM plants

    AGM plants have been through a rigorous trial and assessment programme. They are:

    • Excellent for ordinary use in appropriate conditions
    • Available to buy
    • Of good constitution
    • Essentially stable in form & colour
    • Reasonably resistant to pests & diseases

Deep in stipa

It’s time to cut back those perennial grasses - and on the Portsmouth Field at RHS Garden Wisley the stipa trial is having a haircut

The stipa trial before its spring trimThe plants' foliage looked stunning in winter's early morning light at a time of year when much of the garden was asleep.

Leaving the foliage on over winter also protects the plants from cold and moisture, minimising the chance of winter rot; but now it’s time to cut them back, as they’re starting to look unkempt.

Spring cleaning

Richard Eborn raking dead leaves out of clumps of stipaThis job is done in various ways. I comb out the dead leaves on the evergreen entries, including Stipa tenuissima, with a spring-tine rake starting at the bottom and pulling upwards.

On the deciduous entries, including S. ambigua and S. formicarum, I cut the old dead leaves back to just above new growth using secateurs - you can also use shears - into a slightly mounded shape about 30cm (1ft) high. Then I rake out any remaining dead leaves. For the evergreen S. gigantea entries I cut down their long oat-like flower stems, measure them for the trial, and comb out the dead leaves.
Stipa trial at RHS Garden Wisley, after its spring tidy upAfter this I hoe the bed and cultivate the soil to remove my footprints and improve the drainage (Stipa don’t like it wet). The end result is a neat bed ready for this season’s growth - and another year to perform. Stipas are mostly clump-forming, cool season evergreen grasses, needing full sun and well-drained soil that is not too fertile.

Come and visit the trial in the autumn to see them at their peak.


Useful links

Find out more about RHS Plant Trials

RHS advice: Ornamental grasses

RHS advice: Cutting back ornamental grasses

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