Alys Fowler: thinking of a green wall? Give climbing plants a go instead

On the walk to work, I pass a half-dead green wall. It had gone the way of many green walls, which are often far more work than anyone wants to let on. So I pondered the merits of green walls versus climbers. Climbers won. These are plants that actually want to grow upwards across something vertical and require no more effort from you than giving them something to grow on. Putting up wires or netting may seem a faff, but when you’re on to your third replacement plant and the drip irrigation is still overwatering a particular section of your green wall, vine eyes and wire tensioners may suddenly look more interesting.

One reason people are drawn to green walls is their suitability for small spaces. Many climbers are perfectly content with life in a container, and watering a pot is much more simple than trying to water a wall.

If you decide to grow your climbers in a container that’s, say, the size of a window box on the ground, you’ll have a hard time. Even annual climbers such as sweet peas and climbing nasturtiums need more room for their roots. Most climbers, particularly perennials, have evolved to grow in woodland, whether that’s in the depth of shade, such as ivy, or at the edge, they need something to climb and more often than not that’s a tree. Woodland soils are deep, rich and cool; this is the opposite of many pots that are shallow, exposed and often very hot. Thus, you need the deepest pot you can find. A good nursery-grown climber, whether it’s for a pot or the soil, will be grown in a long tom pot, which is taller than it is wide. For a perennial climber, ideally you’d like a 15-20 litre pot; something you can just about get your arms around. Although this may seem too big, it’s a false economy to use something smaller; you’ll have to water endlessly in summer and eventually re-pot. A five-litre nursery-bought climber potted into a 20-plus litre pot will happily fill a 2m x 3m wall (provided it’s got support to climb up).

The Boulevard collection (‘Picardy’, ‘Parisienne’, ‘Cezanne’ and ‘Countess of Wessex’ are my favourites) are compact with flowers at a height you can see them. Use a rampant Clematis montana or C. cirrhosa and you may find someone else is enjoying the blooms in the flat above.