Drought-tolerant plants for urban gardens
by Rhiannon James
credit: Tony Rodd
Hosepipe bans may be headline news this year but for container gardeners, long sessions with the watering can are a staple of every season. And while watering the pots on a summer’s evening can be very relaxing; finding dejected, drooping plants when this job doesn’t get done certainly isn’t. Automatic irrigation systems are one solution to the problem, but they’re not practical for everyone, so an alternative is to pick plants which can cope with less water.
Drought-tolerant plants are not just a labour-saving option for containers; they’re useful for urban flower beds too where dry soil can be an issue. And, of course, if you want the garden to look great despite the drought restrictions this year, it pays to pick plants that can make the most of any moisture. We asked the experts to name their favourite water-wise plants for urban pots and plots.
“Aloe striatula is a surprising success in the UK: even outside London, this wonderful plant has managed to survive the last few hard winters. It’s a perfect plant for a pot or a hot spot at the base of a wall. I water mine infrequently and holidays can be taken without coming home to dry twigs. The plant is evergreen and subtly architectural with lovely spikes of yellow flowers in June. Be generous with it and use a big pot, or several for a really stunning result.”
James Aldridge, garden designer (www.jamesaldridgedesign.com)
“The beaked yucca (Yucca rostrata) has needle-sharp leaves that could take your eye out, be careful where you place it! This stunning architectural plant will slowly form a sculptural trunk up to nine feet /three metres tall, topped with a rosette of narrow, blue-grey, pointed leaves. It does best in full sun and as it’s slow-growing, it will be happy in a container for many years, but it must have decent drainage.
The Mexican lily (Beschorneria yuccoides) looks like a yucca but it doesn’t have the sharp-ended leaves so it’s much more user-friendly. The rosette of grey-green leaves eventually produces outrageous, arching, red flower spikes that are up to six feet/ two metres tall and rude by any standards. A variety called ‘Quicksilver’ has broader, bolder leaves than the main species. After it has flowered, the central part of the plant dies off but don’t panic as in the meantime, it will have produced a whole clump of new plants (‘pups’) around its base. These go on to repeat the performance all over again. Grow it in full sun on a rich but well-drained soil.
Both these plants come from arid, desert -like locations so they hate to have their roots sitting in wet soil over the winter months. Good drainage and the right soil mix are essential. Put plenty of drainage material in the base of containers. A mix of 50% John Innes No.3 and 50% horticultural grit is the perfect growing medium.
Group spiky plants together for a ‘heat wave’ effect or use them as a pointed contrast to softer and rounder plants.”
Declan Buckley, garden designer (www.buckleydesignassociates.com)
“Many of the Mediterranean species, especially those with grey or glaucous foliage, are a good bet, and sticking to this group of plants will also help to build a theme and some consistency. Amongst the possibilities are the yuccas – a favourite is Yucca aloifolia which will introduce real drama and sharply-defined architecture to the garden. Try it with Euphorbia myrsinites which will provide an interesting and cactus-like ground cover below. Eryngium agavifolium is another favourite for providing a bit of stature.
Agave americana takes this architectural theme to an extreme with huge spear-shaped, leathery foliage in almost metallic blue-grey. The thorns on the leaf edges can be dangerous so it’s best not to use these plants in areas where children might play. Soften the architecture with grasses such as Stipa tenuissima or Salvia officinalis ‘Purpurascens’. Artemisia ‘Powis Castle’ and any of the sparky eryngiums will also help in expanding the composition.”
Andrew Wilson, garden designer, author and chief assessor for the Royal Horticultural Society (www.wmstudio.co.uk)
“Lamb’s ears (Stachys byzantina), which has silver, furry leaves that feel lovely, seems to survive total neglect in hot sun or partial shade as long as it doesn’t get waterlogged. Plants can look a bit sad after the ravages of winter, but they soon produce new growth in spring, and are easily propagated from seeds or cuttings. Lamb’s ears is an excellent ground cover plant, but it also looks good in metal pots alongside cool blue and purple plants such as Tradescantia purpurea and globe thistle (Echinops ritro) or the hot reds, oranges and pinks of pelargonium, pot marigold, rose campion and coreopsis.
Sedums and sempervivums are even tougher. They come in a huge range of colours and forms and hardly need watering at all. Although they are primarily foliage plants, sedum flowers are attractive to bees. Small sedums such as S. cyaneum can be massed together for more impact.”
Helen Wallis, garden worker at Culpeper Community Garden (www.culpeper.org.uk)
“My favourite drought-tolerant plant has to be the Agave americana or the century plant. I planted some in the Spanish Gardens three years ago and they have really prospered. I thought they might not be hardy enough for English winters but they have survived the last two with only one casualty and this was not due to the cold but to the fact that the crown became wet and frozen. Here was a case where water was definitely the wrong thing! Be aware that this agave can grow to a height of two metres and a spread of three metres or more but plants do take a decent amount of time to get to this size. When I was in Barbados a few years ago I saw them used as a boundary. No intruders were going to get past the sharp points the plants have on their leaves!”
David Lewis, Head Gardener at Kensington Roof Gardens (www.roofgardens.virgin.com)
“Pennisetum ‘Red Head’ is a great, (relatively) new plant that’s beautiful, drought-tolerant and loves sun. It looks fabulous in urban gardens.
Generally, grasses can cope best with a lack of water when they’re in the ground as even the most drought-tolerant of plants will need some water when in a pot. That said, they are of course, much less demanding than bedding plants in their need for irrigation.”
Neil Lucas, owner of Knoll Gardens (www.knollgardens.co.uk)
“Watering containerised plants is always tricky in the summer, especially if you go away for a couple of weeks. An automated irrigation system can help you to get over this problem but alternatively, you could create a ‘dry garden’ using plants that require little moisture.
This is all well and good in the warmer months but many of the plants that like to be dry in the summer, like to be frost-free and dry in the winter too; something that is pretty unachievable in Britain. A cool greenhouse or a cloche will help to overwinter some of the most tender plants – keeping them relatively dry will be the key to successful re-growth in the spring – but often in town gardens where space is at a premium this just isn’t possible.
Having said that, herbs such as lavender, rosemary, thyme and oregano are of course wonderful performers in containers, relishing the warm, dry conditions that mimic their natural habitats. Sculptural evergreens are also worth considering; yucca, dasylirion and agave all have architectural merit although their sharp, pointy leaves can come into contact with unsuspecting knees when they’re planted in containers so site them where they can be appreciated from afar. These plants tend to prefer a loamy, free-draining soil which can dry out quickly in a container. Glazed containers are quite good at holding moisture as are some of the GRP and plastic ones. Terracotta containers are absolutely dreadful at retaining moisture but lining them with a piece of plastic will help a lot.
Planting drought-tolerant evergreens in the ground can be a hit-and-miss experience. In towns, agave and yucca both overwinter well with ample grit dug into the soil around their roots – if you can create a good level of drainage, you will hopefully alleviate the problem of excess water around roots which can freeze in winter and kill a slightly tender plant. This really is the key to in-ground success, particularly on a clay-based soil. As the plants age and mature they appear to gain in hardiness. Cistus, ballota and senecio seem to do very well in sunny town gardens and survive both hot summers and cold winters. Although these plants are fairly drought-hardy, a mulch of well-rotted compost applied around the base of the plant in the autumn will help to retain some heat in the soil as winter draws in and also help to retain moisture in the soil in summer.
As with a lot of gardening, how you tend your plants and what you grow will depend on your soil, aspect, prevailing winds and frost zone. Right plant, right place really is the key to successful gardening so take time to assess your site and how it behaves and plant accordingly. You will cut down your workload and grow a far healthier plant in the long run (and if all else fails, you can always consider ‘plastic’ – some of the fake buxus balls are extremely realistic nowadays, but that might well be a contentious point!).”
Kate Gould, garden designer (www.kategouldgardens.com)