Winterizing your olive trees

It might come as a surprise, but what is most fatal to olive trees in winter isn’t the cold – it’s moisture.

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) and have been known to survive temperatures as low as 0 to 4°F (-15 to -18°C).

But if moisture and water join the game, all is lost.

Let us see how olive trees can be protected during winter

You’ll have to proceed differently depending on whether your olive trees grow in the ground or in a pot or container.

Your olive trees are in the ground

If you live in the South, you shouldn’t worry, your olive trees will surely resist winter conditions.

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.

  • With garden soil, create a slope around the base of your olive trees so that water would not flow near their roots.
  • It is important to evacuate water as far as possible from your olive trees in winter: nothing is more dangerous to your tree.
  • Stop all irrigation after having harvested your olives.
  • Don’t fertilize after the harvest. Specifically, don’t add nitrogen-rich fertilizer in fall or autumn.
  • Mulch the base of the olive trees to protect roots from freezing. Using organic plant-based mulch is ok because it would only break down towards spring.

In spring, after freezing is over, you can start irrigating or watering again. This will help your olive trees recover from any wounds due to frost.

Your olive trees are in pots or containers

Once again, if you live in the South, where temperatures never drop below 20°F (nothing much is needed.

  • Place your olive trees in the sun.
  • Water only if the soil is completely dry, and then only small amounts of water.

However, if you live further North,

  • Best is to place your olive trees in a cool and well-lit place where it never freezes.
  • The winter cold in these areas is also very moist, so you must do your utmost to protect your olive trees from moisture.

If you cannot bring your olive trees indoors,

  • Never bring your olive trees indoors in winter.
  • Outside, bring them as close as possible to a window so that they may benefit from the warmth of the house.
  • Mulch the base of your olive trees to protect them from the cold.
  • Wrap the pots with a thick cover, and avoid letting rain fall in.
  • Cover with horticultural fleece, keeping buffer space all around so no leaves touch it. Again, the goal here is to avoid condensation touching the plant since it is a source of moisture.
  • Water as little as possible, and then only if no rainfall reaches the plant.

Read also

Credits for images shared to Nature & Garden (all edits by Gaspard Lorthiois):
Olive tree in winter shared by André P. Meyer-Vitali under © CC BY 2.0

Je souhaite poser une question sur le sujet

Poser ma question

Je souhaite apporter un commentaire

Laisser un commentaire
  • Gabriel M. wrote on 27 January 2019 at 1 h 17 min

    I live in Northeast Alabama. I was told by the people I purchased my olive trees from that I am slightly above the zone for Arbequina olives, even though those are supposed to be one of the more cold hardy varieties, so I was under the impression that I would need to bring them indoors or into a greenhouse, even though this is a bit of trouble (I bring them into a garage with artificial light for now, where it gets cold but never freezes, and I was considering a greenhouse, mostly just for the olives, at least at first). Your article says that they should be fine in the winter though. Are you sure about this? That would be great news, but it seems to conflict with the USDA zoning info I have from a couple of other sources, and the “hardy down to 20 degrees” info I have (we brought them inside just before it got into the teens at night, when some sleet and a light dusting of snow is on the way). But you say not much is needed if I plan to keep them outside all winter. Granted, it’s getting back up into the 40s and 50s most days, but it does stay below freezing in the day and in the teens at night for up to a week or so most winters here, and it snows or sleets usually at least a couple of times a year usually, and occasionally we get multiple inches of snow on the ground continuously for as long as a week. Will the olive trees really be able to handle this? I just want to make sure. They are about 7-8 feet high now, with a lot of time invested, and they are now worth a fair amount and difficult to replace. I thought this might be the case, because my understanding is that the Greek climate in classical times was colder than it is here now, and yet they had olives everywhere already then, but I just want to verify this before i risk their lives. Could you possibly provide some sources for this information? Thank you.

    • Gaspard Lorthiois wrote on 5 February 2019 at 15 h 00 min

      Hi Gabriel, your detailed question deserved a thorough answer!

      In a nutshell, although average temperatures seem to allow for growing olives, the occasional deep freeze puts outdoor olive trees at serious risk.

      Every few years, temperatures drop significantly, reaching 8 or 9 °F in Anniston, Alabama as it did in Jan 2018, 10°F (-12°C) in Jan 2015, 8°F (-13°C) in 2014, 9° (-12°C) in 2003. It always drops down to the lower teens 13, 14°F (-10°C) at some point almost every year. I took Anniston for reference since it isn’t too far from where you are.

      Olive trees, even the hardier Arbequina variety, can cope with routine colds in the lower 20s (-4 to -6°C), but to survive anything colder like the lower teens or upper single digits 8 to 12°F (-13 to -11°C), special conditions need to be brought together:

      • rather large tree already, at least 5 inches (15 cm) across. Younger trees are more vulnerable.
      • no precipitations in the preceding 10 days. As said in the article, moisture kills more than cold.
      • slow descent in temperature, over a week for instance. Sudden drops from 32°F to 10°F (0°C to -11°C) cause more damage than incremental low temps.
      • crucial point is that the preceding months should have been quite cool to ensure the trees haven’t started their spring vegetation.

      Even large olive trees suffer dearly when temperatures drop below 5°F (-15°C), losing leaf buds and twigs and entire branches.

      Two cold fronts swept over Europe, the more severe one in 1956 and a lightly less severe one in 1985.

      The 1956 one saw a mild December and January (temperatures barely around freezing), followed by a sudden snowstorm early Feb that brought temperatures down to 13°F (-10°C), which stayed for a week. A second cold front dropped temps down again to -5°F (-21°C) immediately after that, and a third cold wave meant that temperatures stayed below 13°F (-10°C) for an entire three weeks. That year, four out of five (80%) of all olive trees were cut down because entire trunks had died off – that was five million trees in France alone!

      The 1985 cold front wasn’t as severe, but also resulted in nearly half of all olive plantations being abandoned again.

      In many cases, trees cut down because the cold had killed the trunk were able to send new shoots up, so technically the tree wasn’t “killed”, but harvests were put off for around 4 to 5 years as new shoots grew and were pruned and trained.

      When I saw that historical lows for areas like Anniston flirt with these extreme temperatures (I saw a record for -27°F (-32°C) in 1966 in New Market over in Madison county), I understood you’d be up to the occasional catastrophic devastation as well, if your olive trees were planted in the ground without any form of protection. If planted in containers or cloth sacs, they would be even more vulnerable because the cold would hit the roots, too.

      So your horticulture store’s advice is well grounded in facts. Since you mentioned your grapevines were borderline surviving, expect the same from olive trees. What you can do is make cuttings from the twigs you prune off your olive trees and try transplanting those outdoors once they’ve grown a bit, that could be an interesting and not-too-costly experiment. But since you want to be 100% sure your actual olive trees survive, either keep bringing them in the garage in Jan and Feb, find some kind of well-insulated tent-like structure you can quickly set up that keeps temps in the lower 20s, or for a permanent solution get a greenhouse.

      What is interesting, though, is that olive production increases on years that have a harsh (but not too harsh) winter. It’s said that micro-fissures in twigs and tree stems put the tree in “recovery mode” and it goes all-out in terms of blooming and fruit-bearing. This is actually one of the reasons pruning started being practiced on olive trees. So the saying “if it doesn’t kill you, it’ll make you stronger” is very true!

      I’ll try to work this information into the article, so that it might not be misleading to readers in zones 7b and colder. For those in zones 8a and warmer, that extra 10°F means that olives are a welcome addition to any garden, whether in pots or in the ground, as long as basic winterizing with horticultural fleece is provided on wet, cold days!

      • Gabriel M wrote on 9 February 2019 at 20 h 38 min

        Thank you so much for your thorough research, and for helping me to better understand my options for growing olive trees in this area or in other areas with similar climates. Fortunately, it looks like we will be able to put up a green house before winter next year, which should protect the few trees we have here. In the future, as a more permanent solution, we will probably grow any additional olive trees that we plant in the ground somewhere further south of here, probably in zone 8b near the gulf coast. Based on your advice, this seem like our best options for growing our own olives, given the circumstances.

        I very much appreciate you looking into this for me in such detail. The additional information you’ve provided should be enough to save the lives of the trees I have.

        I am very much looking forward to your olive tree pruning article as well. As you write that future article, please consider one additional question I have. If I am going to keep these trees alive over the winter in my area, it appears that I will need to either bring them inside the garage under artificial light or into a greenhouse, as you suggested in your reply to my comment. I can do this, but I will probably need to prune the trees keep them around 8-8.5 feet high, including the 20 gallon fabric pots, which are themselves about 1.5 feet high. It is my understanding that these arbequina trees typically grow to 8-10 feet high above the ground or the surface of the pot. What I’ve heard so far about pruning olives suggests that we should probably not “top” the trees. Will it be ok to prune the tops of the olive trees to keep them around 7-7.5 feet above ground, rather than 8-10, or will this be harmful to the trees? Do you have any additional instructions about how to prune the trees to control their height without harming them, and in a way that will still keep them as productive as possible?

        Thanks again for all of your help!

Leave a Reply

Your email address will not be published. Required fields are marked *