Well, quite a lot these days. Bookshops are always a good indication of current trends in a country, and American bookstores are piled high with volumes of instruction and inspiration, from Rosemary Verey's two coffee-table volumes on the American Man's and the American Woman's garden, to earnest little paperbacks on 'holistic approaches to horticulture'.
The United States suffer extremes of climate that make British grumbles about the weather seem feeble. The pioneer spirit prevails, however, and even Tulsa, Oklahoma - where the soil is a heavy clay, waterlogged or baked solid according to season, and the weather is largely confined to scorching heat or tornadoes - can manage an extremely impressive Iris Show in May.
The Bay Area of San Francisco perhaps has it easiest, since the climate there almost fulfils my ideal: warm and sunny during the day, cool and rainy at night. Its benefits may be seen merely by strolling around Berkeley, whose street names (Oak, Spruce, Rose) promise much.
In Walnut Street, for instance, the front gardens are as diverse and captivating as the domestic architecture. No two houses are alike except in their use of wood as a principal building material, lending them a sort of folksy modesty that belies the terrifying price of real estate. The sidewalks are broad and separated from the road by narrow beds, often planted with shrubs or bulbs. Every few yards, one passes a mature tree. Californians make use of juniper, senecio, cotoneaster and rosemary, loosely clipped into hedges; but the demarcation between public and private property is also softened by ivy and such small ground-cover plants as Polygonum 'Pink Bubbles', a coyly named but attractive knotweed with dusty rose pompoms about the size of marrowfat peas, and Oxalis chrysantha, which has slender primrose trumpets.
Many shrubs are trained into standards, notably the incandescent bottlebrush, Callistemon rigidus, with its bristling array of bright crimson stamens, purple and white solanums, and heavy-bellied daturas. Roses, jasmine and honeysuckle wreathe around or spill over picket fences, along with a particularly sophisticated variety of black-eyed Susan which has bitter-orange flowers bursting out of hairy, rust-and-green calyces. Plants tend to be grown in clumps rather than borders, and, yes, people do grow agaves. One garden almost converted me to succulents: a Martian landscape of gross sedum, with spikes of unnatural-looking flowers thrusting from their fleshy centres. In their midst, cleaving the air, were giant specimens of the century plant, Agave americana, which looked as if they had been sculpted from aluminium. Not nature as we know it on our verdant island, perhaps, but this garden had immense style.
Texas may be more readily associated in people's minds with rodeos than with the comparatively sedate occupation of gardening, until one remembers how many plants have the botanical suffixes texana and texensis. Austin is on the fringe of the Texas Hill Country, where the spring wildflowers are major tourist attractions. The state flower is not, as popular imagination would have it, a yellow rose, but the Texas bluebonnet (Lupinus texensis), a comparatively low-growing but eye-catching lupin which, from March until May, blankets the country with blue.
The protection and promotion of Texan wild flowers owes much to Lady Bird Johnson, the wife of Lyndon Baines Johnson, who headed a scheme to encourage natives such as Mexican hat (a brown-splotched yellow coneflower, Ratibida columnaris), pink evening primrose (Oenothera speciosa) and scarlet Texas paintbrush (Castilleja indivisa) to colonise freeway verges. Even in May, when the temperature has started upon its inexorable and enervating ascent, roadsides are bright with patches of these flowers, along with the gaudy Gaillardia pulchella, or Indian blanket, best seen in the distance, from a passing car.
The Austin soil is relatively shallow so it only takes a little water to soak it thoroughly. This is just as well, since temperatures often remain at around 100F from May through until late September. One advantage of such heat is that people plant lots of trees, which provide much-needed shade as well as making residential areas of the city unexpectedly and attractively rural. I was unable to discover what was discussed at the Austin Men's Gardening Club (my female host affected to believe that this organisation combined elements of the Freemasons and Iron John), but elsewhere the talk is all of 'xeriscape'. Derived from the term 'xeric', which describes plants that grow in dry conditions, xeriscaping is a conservation-conscious form of gardening in which plants appropriate to the area are grown in near-natural conditions, thus saving water and maintaining the natural ecological balance. Coarse rather than baize-like 'luxury' grasses are used for lawns, and low-maintenance wildflowers are grown in beds and borders.
Such is the range and beauty of native plants that no one need fear that their garden will end up looking like a weed patch. Austin's long-established Barton Springs Nursery, on the picturesquely named Bee Caves Road, is an excellent place to discover which plants flourish in the area (and to buy, should you want to, cowboy garden statuary). One of the most striking plants in their display beds was Commelina erecta, which has blue flowers of an ipomoea-like intensity, but which had not in fact been planted there and is very definitely regarded as a weed. Somewhat resembling (and related to) tradescantia, its flowers are said to act as a botanical Geiger counter, turning mauve in the presence of radioactivity, though I'm happy to say that all the ones I saw were a clear und unequivocal blue.
Other natives are more cherished, and the nursery boasted a whole bench devoted to wild and domesticated salvias, with colours ranging from the pale powder-blue of the lyre-leaf sage, Salvia lyrata, to the brilliant scarlet of the cedar sage, Salvia roemeriana. Particularly attractive is Salvia chamaedryoides: this has germander-like, glaucous foliage, which forms neat mounds and is studded with royal blue flowers. Extremely well-grown specimens cost only dollars 1.59 (just over pounds 1).
Not all Texan plants are tender (the Austin area is visited with single-night frosts - perhaps as few as seven a year, but severe when they come), and there are several which would be well worth trying in an English garden. The standing cyprus or Texas plume, Ipomopsis rubra, is not a tree, but a biennial that in its second year puts up 5ft-tall single stems, with feathery foliage, and produces striking scarlet tubular flowers in May and June. Calylophus drummondianus, the square bud (or box-eye) primrose, is particularly elegant and might best be described as an oenothera in black tie: each clear yellow, slightly rumpled flower has a deep jet throat, from which an inky stigma extends.
Unlike the British, Texans are not afraid of the colour orange, and native helenthaea, and heliantheae such as the huisache-daisy (Amblyolepis setigera) or the zexmenia (Wedelia hispida) enliven gardens as well as the wild. Equally attention-seeking and equally popular, is the Mexican sunflower, Tithonia rotundifolia, with its retina-searing petals surrounding a vivid ginger centre. Smaller, but useful as punctuation, is the flame-coloured Gomphrena globosa, which resembles an everlasting clover. The bright purple variety is the horticultural equivalent of an exclamation mark, and needs to be used accordingly.
Another troubling purple is that of the Tradescantia pallida, which is widely grown. The contrast between the small icing-sugar-pink flowers and the lolling purple tongues of foliage, has always put me off this plant, but at Barton Springs it was grown against a backdrop of wild blue rye. The tall grass, which is similar in colour to oxidised copper, perfectly complements and gently subdues the secretsia, drawing one's eye away from the flowers to the foliage.
On balance - and it is no doubt heretical to say so - I found Texan plants and gardens more interesting than Californian. 'Pacific gardening', as it is now rather grandly known, has undoubted attractions. And yet, nice as it may be to leave salvia and datura in place and unprotected during what passes there for the winter, I should miss having that sense of the year turning. There is something rather dispiriting (not to say occasionally unfortunate in terms of colour and design) about camellias and roses blooming side by side. That masochism for which we British are renowned begins to assert itself. 'It's all rather too easy, isn't it?' one thinks, recalling the battles lost and won against our own late frosts. Although they labour under conditions very different from our own, it is the Texans with whom I had a real sense of horticultural kinship.
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