You might not expect this: what is most fatal to olive trees in winter isn’t the cold – it’s moisture. Protect and winterize your olive tree by diverting excess water and providing shelter and insulation.
If the cold sets in gradually and the air is dry, olive trees are hardy down to 10 to 17°F (-8 to -12°C). Some have been known to survive temperatures as low as 0 to 4°F (-15 to -18°C). When moisture and water join the game, all is lost.
Key facts on winterizing olive trees:
Olive hardiness zone UK: H2-H3
Olive hardiness zone USA: 9b-10
Hardiest olive tree varieties: Arbequina, Picholine and Mission
Protecting olive trees in winter
The basic rules to protect your olive tree from the cold in winter are:
- excellent drainage (no soggy soil)
- shelter from wind (windbreakers)
- fleece or bubble wrap (insulation from the cold)
- moving the tree indoors if too cold (for potted olive)
You’ll have to proceed differently depending on whether your olive grows in the ground (see right below) or in a pot/container (jump to it here).
Winterizing an olive tree in the ground
If you live wherever winters are mild, with only light frost, you shouldn’t worry, your olive trees will certainly survive. However, if you live North or in a region where it rains a lot during winter, you must take a few steps to protect your olive trees.
It is important to evacuate water as far as possible from your olive trees in winter: nothing is more dangerous to your tree.
- With soil, create a mound around each tree so water doesn’t flow towards the trunk.
- Stop irrigating after the harvest.
- Don’t fertilize after the harvest. Specifically, don’t add nitrogen-rich fertilizer in fall or autumn.
In spring, after freezing is over, start irrigating or watering again. This will help your olive trees recover from wounds due to frost.
Growing your olive trees in front of a wall or hedge will cut off the coldest winds. If some portions of your orchard are exposed to cold wind, set up a windbreaker. Even a low stone wall will work wonders and is better than nothing.
Mulch the base around the olive trees to protect roots from freezing.
Use organic plant-based mulch: it breaks down and fertilizes soil only towards the end of winter. Before that, it’s a great insulator.
Wrap the tree with insulation. On smaller trees, a wide swath of bubble-wrap or winterizing fleece helps survive over the first few years. A fully-organic option is burlap or bundles of straw.
Once wrapping the tree becomes impractical, let the tree fend for itself, or wrap just the trunk and scaffold branches. Older trees resist cold weather better than younger ones. In fact, cold weather improves olive-bearing, to a certain point.
Olive tree in a pot: winter care
Once again, if you live in warm areas, where temperatures never drop below 20°F (-6 or -7°C), not much is needed.
- Place your potted olive tree in the sun, near a wall.
- Water only if the soil is completely dry, and then only small amounts of water.
- It’s normal for the tree to lose some of its leaves over the dormant period, about 1/3rd of them will fall in winter.
- Move your olive tree indoors to a cool and well-lit place where it never freezes. Garage, unheated greenhouse, garden shed…
- Protect your olive trees from excess soil moisture by not watering much.
If you cannot bring your potted olive trees indoors,
- Never bring your olive trees indoors in winter. Giving it only a couple days of warmth would trigger growth. This is uncalled for in the middle of winter.
- Outside, bring them as close as possible to a window so they can benefit from the warmth of the house.
- Mulch the base of your olive trees to protect them from the cold.
Lastly, wrap the olive tree as follows:
- Wrap the pot with a thick cover or straw, and block rain from trickling in.
- Cover all branches with horticultural fleece, keeping buffer space all around so leaves don’t touch it. The goal here is to avoid condensation touching the plant since it is a source of moisture. Pack straw around the branches if need be.
- Water as little as possible, and only if no rainfall reaches the plant.
Smart tip about winterizing olive trees
You’ll increase hardiness of your olive tree in winter by protecting it from wind. Set a lattice up on two sides, forming a corner that will cut the worst of colds winds off.
CC BY 2.0: André P. Meyer-Vitali