An estate agent in the Algarve selling a quinta will usually mention the olive trees in the first paragraph of the listing, and with fair reason, since some of them are centuries old. Britain’s climate is harder on olives than Portugal’s, but a surprising number of gardeners grow one anyway, either in a large pot or in a sheltered spot in the ground. They are slow, forgiving and good-looking, and they ask for much less attention than most fruit trees.
How much cold they will take
A mature olive tree can tolerate temperatures down to about minus ten degrees Celsius for a short spell, though wet cold does more harm than dry frost. A young tree is far less hardy, and it needs protection in its first couple of winters: wrap the crown in horticultural fleece, and keep potted trees in a sheltered corner or an unheated porch. In the north of England and Scotland a pot is the safer choice, since it can be moved indoors when a hard freeze is forecast.
Pot or ground
In a pot, use a large container with drainage holes and a gritty, free-draining compost. A loam-based compost such as John Innes No. 3 with a good handful of horticultural grit added suits them well. Start with a pot around 40 centimetres wide and move up a size every few years. Stand the pot on feet so that water runs away freely.
In the ground, choose the sunniest and most sheltered spot you have, ideally against a south-facing wall. The soil must drain well. If your garden is heavy clay, plant on a raised mound or in a raised bed. Spring is the best time to plant, because the tree has a whole summer to settle in before its first winter.
Watering and feeding
Olives are tougher than they look and rot is a bigger risk than thirst. Water a potted tree when the top few centimetres of compost have dried out, and cut back sharply in winter. A tree in the ground needs regular watering in its first summer and very little after that. Feed in spring with a balanced fertiliser, and don’t push growth with too much nitrogen, which produces soft shoots that suffer in the first frost.
Pruning
Prune in late spring or early summer, when the risk of hard frost has passed. Take out dead, crossing and weak branches, and open up the centre of the canopy so that light and air reach the middle. A loose, vase-like shape suits olives and also makes them easier to protect in winter. Resist the urge to cut hard. A heavily pruned olive takes years to recover.
What about the fruit
Don’t count on olives. Even in a warm summer, British trees rarely ripen a worthwhile crop, and fruit that does form is usually too small for pickling. Treat the tree as a foliage plant. The silvery leaves catch the light, and the trunk gets knottier and more characterful with each passing year.
A tree for the long term
Olives grow slowly, and that is part of the appeal. A young tree bought this spring will look much the same next year, and quite different in ten. If you plan to stay in a house for a long time, planting one is a small and rather pleasing act of faith. Buy the biggest you can afford from a reputable nursery, give it good drainage and a sheltered spot, and let it get on with it.
