Plant Profile: Carex

Carex divulsa at Elephant Park, London, in October. Credit: Giacomo Guzzon.

As a landscape architect working mostly in the public realm, I am always looking for tough plants that are visually interesting and will survive with little care.

More than huge and fancy double flowers or variegated vegetation, I am mainly interested in plants that are resilient, robust, and will withstand challenging environmental conditions. The public realm is indeed a very different environment than a private garden where we can easily control the care and limit human-animal disturbance. Continuously faced with these challenges, I became more and more interested in growing different species of the grass-like genus Carex. These plants have proven to be well behaved with different degrees of self-seeding, creating neat clumps, requiring little care, and being very versatile also in difficult locations around trees or in dry shade. Carex can be very long lived in the public landscape when planted in the right spot, and maintenance is really minimal since they are mostly evergreen species. Sometimes in a particularly cold winter with harsh frost, they can be cut back in the spring but not at soil level. They need to be left with enough vegetation to cope with the ‘haircut’, and must be cut at least 15 cm high to avoid killing them.

Carex is a large genus with over 2,000 species in the Cyperaceae family. Surprisingly, only a handful of species are commonly grown in large numbers in the UK and mainland Europe. The majority of the species available are from Asian origin and often with variegated foliage, with Carex oshimensis and Carex morrowii being undoubtedly the two main protagonists in the trade. In the USA on the contrary, there are specialised nurseries growing native Carex species in deep plugs specifically for landscape projects. Moreover, the Mt. Cuba Center botanical garden in Delaware is currently conducting a trial of many common and rare native species, with the aim to assess their potentiality for landscaping and inform the industry and professionals about new worthy plants. In Germany, the ‘Staudensichtung’, the Perennials Examination Group, is currently trialling 48 native and non-native Carex species across Germany and Austria. Through my travels in the US and Europe I have collected several species and I have been growing them and studying their behaviour in the UK and in northern Italy. In my experience some of the most promising candidates with fine leaves are: Carex divulsa (UK native), Carex remota (UK native), Carex cherokensis (US native), Carex pennsylvanica (US native), Carex lenta ‘Kyoto’ and Carex ‘Osaka’ (Japan origin). In the landscape industry we need more of these robust plants that are not particularly showy for garden centres but indispensable for designing resilient and low-maintenance landscapes that nowadays we are all aiming to create.

By Giacomo Guzzon – a senior landscape architect – head of planting design at Gillespies, academic tutor and lecturer in several universities and colleges in the UK.