Will an olive tree in a pot survive an English winter?

Why does the olive raise this question at all?

The olive is the tree most people picture when they think of a Mediterranean courtyard: silver leaves, a gnarled trunk, warm stone. It is also a tree that grows well in English gardens, in the right conditions. The doubt comes every September, when the evenings shorten and an owner looks at a specimen that has spent the summer on a sunny terrace and wonders what the coming months will do to it.

A well sited olive in a pot has a good chance of coming through, but nobody can promise it. Hardiness depends on the tree, the setting, the winter and the care it receives. What can be done is to give it the conditions the RHS describes, and to have a plan for the coldest nights before they arrive.

How hardy is an olive, according to the RHS?

The RHS guide to growing olives says many olives are hardy through most of the UK, tolerating temperatures of -5 to -10°C. It adds a clear caution: leaves and branches can still be damaged by severe frosts, and it notes that winter protection is required in colder parts of the UK. The RHS defines a severe frost as one with a temperature below -5°C (23°F).

Its olive growing guide makes the same point more briefly. Many olives are hardy, but branches can still be damaged by severe frosts, so pot grown trees should be stored somewhere frost free or have their branches covered with horticultural fleece.

Why do pots change the picture?

A tree in the ground has a mass of soil around its roots. A tree in a container does not, and its roots sit closer to the cold. The RHS guide to trees in containers explains that in exposed gardens, roots growing near the edges of a container are vulnerable to freezing temperatures, and suggests wrapping the container in bubble wrap or hessian held with twine.

Containers also bring an advantage. The same guide describes tender trees such as olives as ideal in pots because they can be moved into a frost free place over winter, which the RHS defines as somewhere with a night time minimum of 4°C (39°F), such as a cool greenhouse or conservatory. For a large specimen that cannot be moved easily, wrapping and siting do that work instead.

What should you do as autumn arrives?

The Met Office places the autumn equinox around 22 or 23 September, and this is a natural point to change how a potted olive is looked after.

When	What the RHS advises	Why it matters
From late September	Container olives need regular watering from April to late September; over winter keep the compost barely moist	The RHS names overwatering as the most common cause of loss of container plants
Now	Raise pots off the ground on pot feet or bricks	Lets excess water drain away
Before hard frost	Choose a sheltered position away from cold winds	Cold wind damages foliage as well as frost
Severe frost forecast	Wrap the canopy in a couple of layers of fleece or hessian, and wrap the container	Protects branches and roots on the coldest nights
Milder spells	Remove the wrapping, and replace it when severe frost returns	Wrapping is for severe frost, not the whole winter

Pruning is already behind us for the year. The RHS advises against pruning olives later than August, because new growth will not have time to harden before the risk of frost.

What do people get wrong?

The RHS guide to container maintenance names overwatering as the most common cause of loss of container plants. The first is overwatering. A summer routine carried into November leaves compost cold and saturated, which is exactly what the RHS advice on keeping it barely moist is meant to avoid. Leaving a pot flat on paving, where water collects underneath, makes it worse.

The second is wrapping too early and leaving it on too long. The RHS describes wrapping for very cold winters and severe frosts, and removing it in milder weather. The third is siting. An olive placed in a cold, windy corner because it suited the design in summer is more exposed to the cold winds the RHS advises keeping olives away from.

How does the container help?

The RHS recommends a thick, frost proof container, at least 30 to 35cm in width and depth or large enough to hold the roots easily, with plenty of drainage holes. It suggests a peat free, soil based compost such as John Innes No. 3 with about 20 per cent horticultural grit by volume to improve drainage. The RHS guide to trees in containers adds that frost proof terracotta is heavy, which steadies a tree in windy weather, though the same weight makes the pot harder to move under cover.

When is this not the answer?

If the garden sits in a frost pocket or faces into a cold prevailing wind with no shelter, an olive may struggle whatever is done for it. In that setting a clipped yew or a dwarf pine, both on the RHS list of trees for containers, will give the garden structure without the winter worry. If there is nowhere frost free to move a smaller tree and no one to wrap a larger one on cold nights, it is worth thinking again before committing.

Where should you begin?

Look at where the olive stands now and ask how that spot feels on a cold, windy January evening rather than a September afternoon. Lift the pot onto feet, ease back the watering, and keep fleece somewhere easy to reach. The gallery shows olives in their settings.

The studio gardens are in Linby, Nottinghamshire. Appointment only, by design. You can write to us through the enquiry page to talk about an olive for your garden.