It’s not always easy to say when a plant has had its chips. We’ve all learned to lift and divide border stuff now and then, but when is the now? Your proper professional will have a routine and keep a diary. Besotted amateurs (I’m making a confession) will merely observe and enjoy – even the onset of senility. It gives a border an established look.
When to ditch a shrub can be a much harder question. ‘The slower it grows the longer it lasts’ is a fair rule of thumb: a broom or a mallow that gallops away is soon a diminishing asset; a well-managed rose can go on practically for ever. The real question is not how long it will live but how long will it remain an ornament?
The question came up because one of the terraces in our daughter’s garden on the Riviera clearly begs to be refreshed. There are shrubs with more wood than leaf and flower. An old plumbago has become a thicket, cistus stands stodgy and flowerless, hydrangeas are gracelessly stumpy or leggy, my favourite Solanum laciniatum waves thin flowering shoots above amputated limbs. Only perowskia flourishes in straggly masses of lavender blue.
Is the answer piecemeal chopping, and planting in the gaps? The mixture of old plants and new is rarely a good one. Encouraging the ground-covering herbaceous plants, in this case mainly agapanthus and ‘Society garlic’, as they used to call Tulbaghia violacea, keeps the borders looking filled, but the proportions of height and lower mass soon get out of kilter. You see the bones; it all looks senile. Much better to pull it all out and start again. Then the real foundations of the garden become apparent; in this case olive trees, stone walls blanketed with trailing rosemary, the shining green lemon trees, the pergola with its grapevines and the sentinel cypresses state their simple case. Do we need more furnishing?