When you need to fill in the gaps

The terrace garden look, with tidy plants running between paving, seems artless. It does, however, need plenty of forethought, and a vigilant battle against weeds. At Hinton Ampner, the National Trust garden near Alresford in Hampshire, they have had plenty of opportunity to see which plants will grow between paving since re-laying the terrace in front of the house.

The National Trust has old photos showing the terrace (100 yards long and about five yards wide) 40 or so years ago, when the house was privately owned. Then, huge clumps of campanulas, pinks and potentillas sprawled over the paving. Things have to be different now. With 30,000 visitors expected this year, the paving must be kept clearer, partly so people can walk along it safely, but also because hundreds of feet tramping over the garden will inevitably cause some damage to the plants.

Head gardener Nick Brooks explained that the first essential was to make sure the paving was level, safe, and would last well into the future. The terrace has been laid on hard core and sand, and more sand is being brushed into the crevices. Mr Brooks and his team have made their own compost of sterilised soil, coarse grit, bark and leafmould which is brushed into the paving before planting.

They have planted very low growing plants such as sedum acre, small thymes and aubrieta which they hope will confine themselves to the gaps between the paving. Towards the sides of the terrace pinks, small artemisias, and geraniums such as G. procurrens will form little mounds. At the edges, larger plants will be allowed, including hypericums, campanulas and perennial wallflowers. These will grow irregularly along the edges, and the idea is that a path will weave around the clumps.

When trying to establish a new plant, it is worth seeing if it can be divided into two or three pieces before planting. This works with small sedums, thymes, camomiles and with the highly successful Pratia pedunculata.

Some of the greatest successes plant themselves. The little Erigeron karvinskianus seeds itself into paving, as do some campanulas and geraniums. Sadly, the greatest successes at seeding themselves are couch grass and the dreaded small-leaved oxalis. This oxalis, which makes ground elder seem positively friendly, is not difficult to pull up. But as fast as you pull one plant up, three more have grown somewhere else.

If you follow Mr Brooks' advice and use a sterilised soil mixture in the first place, you won't import weeds. He also suggests that after planting, some sand should be brushed around the plants. Weeds which then seed themselves will be easy to pull out while they are small.

At Hinton Ampner they are taking the replanting slowly, experimenting to see what is successful. Whether you have 500 square yards of terrace in the country, or a few square feet behind a town house: what is needed is well planned and well-laid paving, plenty of experiments, and plenty of patience.

Hinton Ampner Garden, near Alresford in Hampshire. Open at weekends, Tues, Wed and Bank Holiday Mons. Adults pounds 2.50, children pounds 1.25