How not to make a roof garden

In Alcalá de los Gazules and other pueblos blancos of Andalucia, where houses tend to be built one on top of another, it is unusual to have a garden attached to your house. Many of the locals grow fruit and vegetables in nearby plots of land called huertos, and adorn their whitewashed walls and windowsills with pots of geraniums. But the traditional English-style garden, with flowerbeds and lawns, is rarely seen.

Undaunted, when we moved here in 2008 I decided to create a garden on our large flat roof. I had a vision of a leafy haven for insects, birds and butterflies, with jasmine and potted citruses to scent the warm evenings, bougainvillea and geraniums for a riot of colour, and of course home-grown, sun-ripened tomatoes, peppers and herbs. The cats would have somewhere fun to frolic and snooze. Everything would be grown in pots, so we would be able to sit out and read all day, confident in the knowledge that we would would never again have to trim a privet hedge or mow a lawn.

The locals use their roof terraces to hang out the washing, tie up their dogs or occasionally keep poultry. Sitting out on the roof is purely for mad foreigners, and growing flowers up there is just plain weird (though the odd cannabis sativa plant has been spotted). But we carried on regardless, lugging sacks of compost and gravel mulch, giant planting troughs and clay pots up two flights of stairs in 30 degree temperatures.

We invested in four ridiculously expensive plastic troughs, each 120 x 60 cm, made of a kind of durable plastic which looks just like terracotta. The real thing would have been so heavy that the roof would probably have caved in under the weight, and would have absorbed water faster than I could top them up. We used broken polystyrene instead of crocks for drainage, again to save weight, and mulched them with two inches of pretty pink gravel. We put up a trellis for things to climb up and provide us with some privacy (a mule-track snakes up a cliff just behind the house).

We get no rain at all from May to September, and temperatures average 35°C in July and August, so watering has to be done daily after sundown. Fortunately we already had a water supply up there, though it was two years before we got round to attaching a hosepipe to it, when our plastic watering-can finally gave up and melted in the heat.

Lantana camara, the colours of
the Spanish flag

A compost heap is out of the question of course, and what goes up those two flights of stairs must eventually come down again. I made the mistake (once) of using a biodegradable plastic bin-liner to store leaf-mould, which biodegraded rather more quickly than expected and deposited said mould all over my feet when I picked it up.

The first few months were reasonably successful. Our little lemon tree produced nine lemons, enough for a whole summer's intake of G&T. The bougainvillea, hibiscus, plumbago auriculata, Spanish flag plant (lantana camara), mandevilla and Spanish jasmine (jasminum grandiflorum) grew vigorously in the troughs and soon had to be attached to the trellis with garden wire. Trailing geraniums planted amongst the shrubs flourished, as did the pots of thyme and rosemary. Cherry tomatoes and chili peppers germinated rapidly from seed and were quickly potted on and placed outside to enjoy the sunshine; no need for hardening off here, as the temperature rarely falls below 4 or 5 degrees even in midwinter.

The first setback was the wind. Our wind is so famous it has its own name, the Levante, which means “from the east”. Our garden faces east. That damn wind whips through the mountains on its journey from the Sahara and hits us full in the face, ripping washing from the line, overturning garden furniture and tossing the smaller pots around like shuttlecocks. Bye-bye, little tomato plants …   Then came the geranium moths, nasty little brown buggers which lay their eggs in the stalks so the plants rot from the inside. Their official name is cacyreus marshalli and they came over from Africa in the 1990s doing untold damage to Andalucia's most celebrated perennial. Not wanting to spray everything with pesticide, I had to rip out the affected plants (nearly all of them). Fortunately they don't like my scented geraniums, which have insignificant little pink flowers but a wonderful lemony smell and grow easily from cuttings.

The next plague to strike was woolly aphid. I spotted little white chewy blobs on the stems of the lemon tree (by now, and in fact ever since, bereft of lemons). Inside these blobs live tiny red aphids. Anxious to retain my green credentials (nothing gets through the white goo anyway) I carefully removed them all by hand and thanked my stars they hadn't discovered the bougainvillea, which they apparently love.   The ants mopped up the ones I missed.

The following year I had wised up to the Levante terrorist threat and put the tomato plants (Roma and Tumbler varieties) in large heavy pots, placed up against the wall for protection. Dutifully watering them twice a day I managed to raise an impressive crop of fruit of both types, but the Roma succumbed to blossom-end rot and the cherries were tiny with chewy thick skins. At the time of fruition you could buy fabulous vine-ripened toms in the market for 50 cents a kilo … Another lesson learned.

The herb garden fared slightly better, especially sweet basil, coriander and flat-leaf parsley grown from seed. But I had sown them too late (April) and by the time they were ready to plant out (June) there was no shade left and they literally baked in the soil.

By year three the soil in the troughs must have been exhausted, despite regular feeding; the flowering shrubs gave a very poor show. Removing two inches of gravel mulch and replacing the top six inches of compost was backbreaking and messy. I'm not even sure it did any good, but we'll see what this summer brings. I've since been told that plumbago prefers damp shade and lantana hates being in pots! The jasmines are still thriving, filling the air with their exquisite scent, but the delicate white flowers tend to shrivel in the wind. The happiest plants are the bougainvilleas, especially a dwarf bush variety, and hibiscus, which flower all through the winter.

Happy grasshoppers

I finally admitted defeat last year and replaced the flowering perennials with a variety of low planters full of kalanchoes, cacti, succulents and sedums, mulched with white pebbles and seashells. They sneer at the wind, adore the searing sun and don't mind at all if I forget to water them for weeks on end. They have been colonised by a family of giant grasshoppers and some geckoes, who between them dispose of unwanted bugs more efficiently than any spray. I grow my herbs on the windowsill over the winter and freeze them, and I buy tomatoes and peppers in the market.

Maybe I am getting lazier as I get older, or the languid Spanish heat has drawn me into the culture of mañana - never do today what you can put off till tomorrow. But these days a deckchair and a good book have a lot more appeal than a sack of compost and permanently black fingernails ...