Late Autumn is a magical time to visit Knoll Gardens, one of the top nurseries for ornamental grasses in the UK (the other being Sussex Prairies). On one of my recent visits, I attended a masterclass for designers with owner Neil Lucas. He was generous as ever with his knowledge of how to choose and place grass in the garden.
He started with a couple of golden rules. Broadly speaking there are two main types of ornamental grass:
1. Full sun types: Deciduous, tall, deliver the ‘wow’ factor. Best to chop them during late Winter, say Feb/March. Chop the stems into say 3 or 4 sections and leave them to decompose on the ground where they fall.
2. Dry shade types: Evergreen, generally shorter. No need to clip unless they are looking tired. But do NOT do so during their dormancy period, instead they must be actively growing. The active growing season for most ornamental grasses is April-May-June.
Perfect for the needs of today’s time-pressed gardeners who do not want to be slaves to their garden, grasses are forgiving and generally require minimal care. No need for feed or fertiliser. Do not touch or turn their soil if at all possible. Do mulch. Can even be chopped mechanically with a hedge trimmer, but not a strimmer because they tear too much.
Neil Lucas nominates the “Big 5” grass families – drum roll…
Pennisetum – intriguing, fluffy, like pipe cleaners. (Varieties recommended: Dark Desire - very sultry dark, bushy & tactile. Velosum, a bit less hardy, Macurum with pretty blond heads.)
Panicum – light bright frothy dots. (Varieties recommended: Shenandoah, Merlot, Virgatum.)
Calamagrostis – tall vertical spires
Molinia - shorter vertical spires growing from lumpy clumps like those growing on lowland heath. (Varieties recommended: Arundacsia (2m tall), camellia (1.5m), Hydsverg (looks most like our lowland heath plants, distinct clumps) - all look good with Verbena.)
Miscanthus - soft brushes. (Varieties recommended: Flamingo, Starlight.)
But there are other useful grasses beyond the Big 5 – for instance:
Stipa tenuissima – very attractive and tactile, like blond horse hair.
Carex (strictly speaking it’s a sedge not a grass) – shade-lover. Most dependable one is Ice Dance - perfect for dry shade, but can crowd others out. Other varieties: C. divulsa (UK indigenous), C. remota (UK indigenous), C. ‘Silver Sceptre’, C. arenaria (sand dunes).
Sesleria autumnalis: telly tubby mound, a bit shaggy, evergreen, dry shade lover.
Melica uniflora ‘Alba’ - magical rice particles - even finer than M. altissima. Much sought-after for RHS Chelsea Flower Show as I found to my cost when sourcing for the show last year.
Anemanthele lessiana - deciduous.
Hakonechloa – soft low fluffy edge planting, quite happy in sun or shade.
The longer-lived grasses are Miscanthus, Panicum, Hakonechloa. Others have to be allowed to self-seed to maintain their presence.