Gardening column: Plant sense

‘How do I know what soil I have?’ I was asked last week.

The garden was north-facing, raised, with two fine evergreen shrubs, a camellia and a rhododendron. Close by was a healthy medium-sized cherry tree with a well-balanced habit. The garden already has some good keystone plants and the healthy appearance of the evergreens revealed a great deal about the soil. Then I noticed a lovely climber next door. The success of this vine showed why you should question everything.

According to the Royal Horticultural Society’s Encyclopedia of Gardening, there are five main soil types: sandy, peat, clay, chalk and silt, and soils are classified by how much clay, silt and sand they contain. You can work this out by squeezing the soil (moistened slightly if dry) to see how it responds. Sandy soil will feel gritty and loose (hence free draining) between your fingers, whereas clay soil will be sticky and can be made into balls. Choose plants that suit the conditions you have.

The happy condition of the shrubs told me this was a moist soil, with a pH on the acid side of neutral. Camellias and rhododendrons dislike dry and alkaline soils. In such conditions their foliage would have been pale yellow with chlorosis. The camellia showed no sign of scorching, indicating the semi-shaded position suits it. Drainage wise there is probably quite a high clay and organic content as both shrubs seemed unperturbed by the raised, and therefore drier, bed, the rain shadow of the house and the competition from the tree.

So what was the exotic climber next door? It was Campsis, a late-flowering vine with large trumpet-shaped flowers. They say Campsis is on the tender side and it needs good sun to flower, well this one is blooming beautifully on a sheltered north-facing wall in Joppa, on the outskirts of Edinburgh.

Rebecca Govier, Garden Designer (0781 750 5571, [email protected], www.greenedgegardendesign.co.uk)