Clear out the yard, but spare the concrete

WORKSHOP: Gill King and Michael Griffith-Jones want ideas for their courtyard, yet they don't want to lose the stone floor

Our home is a brick (c1914) two-storey warehouse in south London. We would like some ideas of how to treat a walled courtyard space, approximately 34ft by 16ft. This is currently a single storey extension to the main building. We plan to remove most of the roof, leaving a shelter nine feet deep at the north-west end and knock out the windows and doors to create arches in the 10ft high wall. It has a concrete floor which we do not propose to take up, although we can break it up in certain areas for drainage purposes. This area is on an east-west axis and is quite overshadowed by largeish trees over which we have little control. We think built-up beds will be necessary and want to include a pond."

When Gill King and her partner, Michael Griffith-Jones wrote this letter, they were living in a Portacabin, waiting for builders to finish work on their warehouse, once a ceramic tile works. By the time I caught up with them, they had moved in and the area where the Portacabin had been standing had become another cause for concern. It is beside the extension they talked about in their letter: a rectangle, mostly rubble, roughly 18ft by 10ft filling the north-east corner of their plot and heavily overshadowed by a large sycamore. Not the most propitious spot for planting.

The only earth in the whole place is a thin strip, just four feet wide squeezed in between the outside wall of the extension (which was to become part of the garden) and the tall, battered chain link fence that is their northern boundary. It's just about wide enough to walk down without knocking the corners off your elbows.

Ms King does not mind the lack of earth. "I've got very attached to our tarmac" she said. "I like the idea that once, huge 40ft lorries backed in and out of this building. We've kept so much of the structure. We don't really want to start digging up the hard surfaces."

Ms King and Mr Griffith-Jones are both social workers in their forties and they want the garden to be a peaceful refuge, a soothing place, with the white noise sound of water burbling in the background and great waves of scent to billow past the seats they have already put in the walled courtyard.

By taking the roof and every other roof joist away from the lean-to extension, they had created a very successful walled-round courtyard with a pergola- like roof. They had taken out the old Crittall windows, leaving three arched openings along the north facing wall. The old, cracked concrete floor was still in situ, but the walls on the inside of the courtyard had been whitewashed, giving the space a curiously Moorish air.

I suggested a rectangular pool in the centre of the courtyard, built to the same proportions as the yard itself. A raised pool would break up the space more effectively than a sunken one, and would be easier and cheaper to build. Faces brightened at the thought that the beloved concrete would not have to be sacrificed, but fell when I suggested hedging all the way round the raised pool with box. This would grow up to the level of the water and then be neatly cut across the top, so that the water would look as if it was contained in low hedges of box, rather than in breeze-block walls.

Could the box hedges be planted in troughs, asked Ms King. "No" I said firmly. They could drill a border round the outside of the pool and plant in that. It would still be less trouble than excavating a space big enough for the pool itself. But the look on their faces convinced me they would do nothing of the sort. The pool, with a simple submerged jet in the centre to give the required background noise, would be simple to install. At the end of summer they could fix a net over the top of it to catch the leaves that fall in huge numbers from the sycamore.

On the outside of the courtyard where the thin strip of earth runs between the wall and the chain-link boundary fence, Ms King and Mr Griffiths-Jones had dug big planting pits underneath each of the windows, and had already set Clematis montana in each of them. They had three different kinds: 'Tetrarose' which has big lilac-rose flowers, 'Elizabeth', which smells of chocolate and the more deeply coloured 'Pink Perfection'. If I had been choosing, I would have spread the flowering times of the three clematis more widely by choosing just one Montana, with a Macropetala clematis for early spring and a Jackmanii type for high summer.

Set on the outside of the courtyard wall, the plants faced north. But if the stems were led in through the window spaces, they could be trained up the inside south-facing aspect of the wall, where they would not only flower better, but be more easily seen by Ms King and Mr Griffith-Jones. When the clematis are large enough, they could scramble along the open pergola-like roof joists.

Since this was the only earth these two gardeners have they need to make the most of it. I suggested vines such as Vitis coignetiae which could cope with the shade cast by the sycamore, Vitis vinifera 'Purpurea' and a rumbustious rose such as the white, cluster- flowered 'Rambling Rector'. It only flowers once, but then so do the Montana clematis. For late summer, they could try white-flowered solanum, and in the sunniest spot, the tropical looking climber Campsis x tagliabuana 'Mme Galen'. The vines would give a feeling of luxuriant leafiness. The clematis, rose and solanum would add colour. The campsis has foliage as good as its brilliant orange trumpet flowers. All could be trained through the window arches and up the inside courtyard wall to the roof beams.

Inside the courtyard building, Ms King and Mr Griffith-Jones had terracotta tubs formally planted with pairs of spiky mahonias, yellow-flowered fremontodendron and Magnolia grandiflora, the big-leaved evergeen bull bay that comes from the Florida swamps. They aren't adapted to life in containers, but in the short term, they may be happy enough, especially if the watering system Mr Griffith-Jones talked about is installed. They will all need regular feeding. I find Osmacote slow release granules the easiest and best method of feeding. Used in spring, they provide food for the next six months.

If they built a raised bed along the far east-facing wall of the courtyard, Ms King and Mr Griffith-Jones would make life easier for their plants. They would also give themselves room to build up satisfying plant groups - difficult in an 18in container. But it would mean drilling holes for drainage in the concrete at the bottom of the raised beds. Although I dared not suggest it, I would then cover the concrete throughout the courtyard with creamy gravel, making sure I had cracked up enough of it underneath to allow flowers such as erigerons and violas to self-seed.

The space outside the courtyard was more difficult to resolve, overhung and dripped on by the sycamore. But since Mr Griffith-Jones seemed to like formal arrangements I suggested dividing the space visually into two squares by standing a bay tree in a pot in each of the two halves of the long rectangle.

Neither of them wanted to remove the rubble here, so the plants would have to cope with shade, drought, and starvation. If they could be started off in pockets of good earth, excavated in the rubble, they would have at least a fighting chance of survival. Dark-leaved bugle, arums with marbled leaves (Arum italicum 'Pictum'), epimediums with good foliage on thin wiry stems, creeping lamiums, pink and white purple-leaved Viola labradorica (or even the bullying yellow flowered), tellima and spotty- leaved pulmonaria would all be worth trying. Once planted, they could be left to weave themselves together into a low Persian carpet of changing leaf and flower. Small ferns such as Polypodium vulgare 'Cornubiense' might survive too.

But I am worried about those magnolias, which are programmed to grow into massive stately trees, at least 15ft high, 10ft wide. I can imagine their roots soon banging against the sides of their pots shouting "Help! Let me out." I hope Ms King and Mr Griffith-Jones will be able to hear them.