Water is valuable, so we need to make the best use of what we get, writes Jane Powers
No sooner had I decided to write about conserving water in the garden than it rained for two and a half days. Parts of Ireland received almost a month's rainfall in those inundated hours. In our dehydrated garden, such wholesale saturation was entirely welcome. The conditions were perfect for a spot of mulching, with all those gallons of water deposited into beautifully warm soil.
So, after weeding, I covered the soil in our small vegetable beds with grass clippings (not too thickly, or they get slimy when they begin to break down) to lock in the moisture and warmth, keep down the weeds and preserve the soil structure. Now, when I look at the blanketed patch, I know that the soil is nicely protected, and I feel snug and happy - the way you feel when you see a sleeping infant safely tucked up in its cot.
I'm happy also because I know I'm doing my bit for the environment by conserving water - and what a lovely, virtuous feeling that is. Mulched beds need little watering compared with those that are unprotected, whose moisture is squandered by heat and wind.
Indeed, mulching moist and weed-free soil is one of the best ways to reduce water use in the garden. Organic materials - grass clippings, straw, garden compost, spent mushroom compost, shredded wood and bark, cocoa shells - all rot down eventually, nourishing the soil in the process. Gravel or stone chippings are inert, but they need to be topped up after some years. This kind of stony surface looks just right when used around grey-leaved and succulent plants - in other words, plants that need little water to survive.
These drought-resistant flora are staples of the water-saving garden. Of course, they're not called for (or even appropriate) if you're gardening on heavy clay in a damp county. But if you live anywhere along the coast, where the soil is generally light, or in an urban area where the soil is tired and thin, and where high walls cast a "rain shadow", then it's wise to grow plants that need little water.
Suitable species come from areas where rainfall is naturally low or where the vegetation is subjected to the drying effects of sun and wind. Seaside plants, growing in sandy soil and exposed to salt, are especially drought-resistant. So are plants from regions such as the Mediterranean, southern Africa, Australia, California and South America and from prairies, steppes, maquis and garrigue.
Such plants have roots that may be long and thin, plumbing the depths of the soil for moisture, or that may form a far-reaching underground network, drawing water from a large area. Their foliage is designed to resist desiccation through exposure, and it may be insulated with hairs or fur (as in verbascum), or be blue or greyish to reflect the sun (smoke bush: Cotinus coggyria). Waxy leaves, such as those of bergenia, are slow to transpire moisture, while the small and hard leaves of many herbs and Australian plants require little water - and are parsimonious about giving up what they have. Plants with succulent leaves, such as sedums and sempervivums, are like vegetable camels, carrying personal stores of water to see them through the dry times.
A plant that is definitely not shy about drinking water, and is far too cosseted in gardens, is grass - that is, the lawn. If you want to conserve water, reduce the size of the lawn. At the very least, make it more water-retentive by spiking it in early autumn, or using a hollow-tined fork to make holes about 8-10cm deep. Such aeration opens up compacted soil and allows water to travel deeper.
It's a waste of precious water to pour it on to lawns, but other parts of the garden need help during dry periods. Newly planted areas and food crops may need watering, but do it in early morning or evening, so the heat of the day doesn't suck the moisture right back up again. Watering deeply and infrequently is better than little and often, as the latter promotes shallow roots, which are constantly thirsty.
The very best way, though, to create a moisture-conserving garden is to work more water-retaining organic matter into the soil: dig it in, add it to planting holes or leave it on top, then let the worms till it in for you. The cheapest and closest-to-hand material is our own, home-made garden compost - a substance that a newly green nation is making by the binload, following the introduction of pay-by-use refuse charges. Which prompts an obvious question: if the current composting activity is anything to go by, is the only way to spur a similar interest in saving water to meter it and charge for it?
PLANTS FOR THE WATER-SAVING GARDEN
Besides the plants listed below, most Mediterranean herbs - thyme, rosemary, fennel, oregano and so on - are non-thirsty candidates. Likewise, many bulbous plants tolerate drought, including alliums, cyclamen and small-species tulips.
GROUNDCOVER AND LOW-GROWERS
Bugle (Ajuga reptans), lady's mantle (Alchemilla mollis), sea pink (Armeria), Bergenia, Brunnera macrophylla, Convolvulus sabatius, Dianthus deltoides, Diascia, Echeveria, smaller hardy geraniums, ivy varieties (Hedera: it crawls, as well as climbing), Sempervivum, periwinkle (Vinca).
BORDER PERENNIALS
Achillea, bear's breeches (Acanthus), Agapanthus, Alstroemeria, Crocosmia, Japanese anemone, foxglove species (Digitalis: the native species, D. purpurea, is biennial, but it self-seeds; look out for the pretty white form), Dianthus carthusianorum, globe thistle (Echinops), sea holly (Eryngium), smaller Euphorbia species, Gaura, larger and more sprawly hardy geraniums, Corsican hellebore (Helleborus argutifolius), stinking hellebore (H. foetidus), red hot poker (Kniphofia), Lychnis coronaria, Osteospermum, oriental poppy (Papaver orientale), Phlomis russeliana, Solomon's seal (Polygonatum), large Sedum varieties, Sisyrinchium, lamb's ears (Stachys byzantina), Verbena bonariensis (short-lived).
WOODY PLANTS
Wormwood (Artemisia), Ballota, Brachyglottis 'Sunshine', butterfly bush (Buddleia), rock rose (Cistus), Convolvulus cneorum, smoke bush (Cotinus coggyria), Dodonea, wallflower (Erysimum), Euphorbia, Grevillea, Griselinia, Hebe, sun rose (Helianthemum), Hypericum, lavender, catmint (Nepeta), Russian sage (Perovskia), shrubby cinquefoil (Potentilla), rue (Ruta graveolens), cotton lavender (Santolina).
ARCHITECTURAL PLANTS
Agave, (the hardiest is A. parryi, but other species survive in warmer areas), Beschorneria yuccoides, seakale (Crambe maritima), cardoon (Cynara cardunculus), giant echiums (E. pininana and E. wildpretii) cotton thistle (Onopordum acanthium), Osteospermum, Paulownia (prune the branches back very hard in early spring to keep it compact), Phormium, Yucca, Verbascum.
ORNAMENTAL GRASSES
Many are drought-resistant, but these are readily available: Pheasant grass (Calamagrostis arundinacea, also known as Stipa arundinacea), pampas grass (Cortaderia selloana), Bowles' golden grass (Milium effusum 'Aureum'), giant oats (Stipa gigantea).