TWO parched winters in a row; a Thames Water hosepipe ban which, if the Environment Agency has its bossy way, will ripen into a full-scale drought order; a borehole drilled in the grounds of the Royal Hospital; all this can mean only one thing — rain.

Throughout the Chelsea Flower Show, garden designers are cursing this sudden improvement in our horticultural fortunes, and who can blame them? The £20,000 garden settee clad in an old mackintosh; the tulips cowering under inverted Styrofoam cups; the artfully simulated dry river bed in full flood; the chipped bark path that turns to tannic slurry: these are the tears of things.

To highlight the misery, this year the Royal Horticultural Society required all involved in the build-up to the show to don a fluorescent yellow jerkin. The resulting scene resembled a swarm of giant and singularly bad-tempered glow-worms glimpsed through Scotch mist. Here and there, only the scarlet tunic of a Chelsea Pensioner punctured the gloom. I have often thought that the RHS should offer the public a limited number of tickets for this period of crazed construction and downpour-dodging. It is possibly the most impressive aspect of the entire event.

Miraculously, they have all done it again. The show, conceived in a drought, delivered in deluge, goes on regardless. This year’s is one of those Chelseas that consolidate rather than revolutionise. There are few new departures and rather a lot of déjà vu. But this is far from a complaint: we cannot always be innovating and good ideas bear repeating. More importantly, many of this year’s show gardens seem to have been made with a care as to whether or not they would work in reality.

This incursion of practicality is, I suspect, a happy by-product of the drought. Some designers have attempted explicitly low-water gardens deploying xerophytic or Mediterranean-type plants, lashings of insulating gravel and large expanses of stone. Others have merely moderated their customary exuberance, using a more limited planting palette and showing a shyness with the hose, whether by design or force majeure. Either way, the results are good: these are gardens rather than al-fresco art installations or obscene exercises in floristry.

A fine example of the first kind is the Saga Insurance Garden designed by Cleve West. It presents a world tour of culinary and medicinal plants in a series of large gravel borders that have something of the widely spaced, specimen-by-specimen rhythm of an old physic garden. Any repro nostalgia is dramatically dispelled, however, by three giant concrete sculptures described as proffering “quiet contemplation as they wait for the rain” — a short wait as it turns out.

By contrast, Robert Myers has eschewed eclecticism in an unashamed and delightful tribute to Campania, one region of Italy where good horticulture and erratic water supplies have coexisted harmoniously for millennia. The Costiera dei Fiori Garden includes a picturesque, pergola-screened potager, a playful majolica-tiled terrace, and a rocky bank replete with citrus, prickly pear and the native aromatics of the macchia Mediterranea.

While these two designs embrace drought, others face the challenge by preserving the abundance of our established horticultural repertoire and simply restricting the areas in which it is displayed. Lawns are replaced by stone or wooden pathways and terraces. Borders become jewel boxes, containers for concentrated colour and texture that should thrive even on short rations.

For example, Tom Stuart-Smith’s Daily Telegraph Garden presents a steppe-like sward of bearded iris, verbascum, salvia and ornamental grasses. The brilliant, dancing quality of this planting is offset by walls and tubs of richly rusted steel and weathered oak boarding — a clever contrast of youth and old age. Also notable are the specimens of Viburnum rhytidophyllum, quite possibly the most boring shrub in British cultivation but beautifully pruned here to expose its sinuous limbs: Stuart-Smith has found the sculpture in the block of stone.

Sarah Eberle’s garden for Bradstone is less vivacious, more monumental, with a bunker-like viewing deck and great sweeps of modernist masonry. Yet it works magnificently as a way of introducing elements of cultivated and wild landscape into a heavily built space. It leaves one wishing such designs could be realised in, say, the petrified purlieus of the South Bank. Drought notwithstanding, this is also a garden in which water plays a large part, and some of its aquatic plantings (the army of thrusting horsetails alongside the shingled brook, the elegiac veil of reeds in the main pool) aspire to a naturalistic and sculptural simplicity. The water, by the way, comes courtesy of Bradstone’s domestic sustainable drainage system which collects rainwater for the garden from the house walls and roof and stores it in underground tanks. We will be hearing more of such systems in years to come.

For the moment, however, that all feels academic as one cloudburst follows another. This year Chelsea will be well worth a visit on the last two days. With the chill wet weather, plants that would normally be exhausted by their months of coaching will only just be hitting their stride.

The RHS Chelsea Flower Show continues in the grounds of the Royal Hospital, Chelsea, until Saturday, May 27. All tickets must be bought in advance. For further details see www.rhs.org.uk/flowershows or telephone 020-7649 1885.

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