Olive trees are hardy down to -5 degrees and must be protected from frost and snow both in the pot and outdoors. The crown of the olive tree in particular must be protected against the cold with a fleece. Roots and trunk can be protected from frost over the winter using leaves, brushwood, coconut and felt mats.
How are olive trees wintered?
Olive trees are overwintered bright and frost-free at 5 to 10 degrees in late autumn after long periods of frost. This can happen in the hallway, winter garden or greenhouse. Overwintering outdoors is possible if the bucket is protected. To do this you need a coaster made of wood, for example, a jute bag to protect the bucket and a fleece to protect the crown. Outdoor plantings can also be protected with a frost monitor.
Are olive trees hardy?
Olive trees originally come from the Mediterranean region. The winter hardiness is thereforeonly limited Temperatures down to -5 degrees Celsius are tolerated by the common varieties without any major problems. Only a few varieties can tolerate permanently lower temperatures from -10 degrees Celsius. These include:
- Aglandau
- Arbequina
- Bouteillan
- Cornicabra
- Empeltre
- Frantoio
- Hojiblanca
- Picual
For all other varieties there is arisk of irreparable frost damageParticularly mild regions in the Rhine Valley or around river valleys are characterized by winters that are not too severe. Overwintering outdoors is usually easy here. Especially in eastern Germany, in the low mountain ranges, the Alps and other high altitudes, temperatures drop early and persistently. For these areas, it is therefore recommended to overwinter in suitable winter quarters. This should be as bright, cool and protected from the weather as possible. In addition, direct sunlight should be avoided to prevent overheating.
When do olive trees overwinter?
No later thanwith the onset of night frosts winterization measures should be taken. It is therefore advisable to take a regular look at the weather report between October and November. Even just a few very cold hours can cause permanent damage to the Mediterranean plant.
Nevertheless, it is recommended to cultivate Olea europaea outdoors for as long as possible. Slightly sub-zero temperatures usually do not harm the tree. In this way, the plant can be slowly introduced to cooler temperatures over several years.
In contrast, pests and pathogens in particular are always killed effectively and rigorously. Especially before a planned move to a winter quarters with other plants, any diseases can be avoided in advance.
In a protected and covered place, the olive tree can tolerate temperatures of up to -5 degrees Celsius.
Olive tree pruning in winter
Basically, regular pruning of the olive tree is not necessary due to its slow growth. However, individual cutting measures can be useful. The ideal pruning time is early spring. In any case, new growth should not have started yet, otherwise growth will be delayed in the coming period. Alternatively, the cut can be done in late autumn during overwintering.
For a comprehensive pruning, the following steps are recommended:
- shorten crown shoots that have grown out of shape
- thin out inner branches
- Remove competitive branches
- cut off shoots growing directly from the trunk
- remove dead branches and cones
All important information about cutting types and dates is summarized here. Additional cutting instructions are shown in the following video.
Overwintering olive trees outdoors
In milder regions, the olive tree can easily stand outdoors all year round. However, depending on the type of cultivation, i.e. whether the tree was planted directly in the ground or in a pot, there are a few tips to consider.
Terrace, balcony and carport
Terrace, balcony and carport are ideal locations for olive trees. It is important that the plant is as close as possible to the house wall. These places offer natural protection from weather influences such as snow and rain. At the same time, they receive enough light. Even during winter dormancy, which is triggered by low temperatures, the plant still needs light exposure. However, direct sunlight is not absolutely necessary.
In case of particularly severe frosts, further precautions must be taken. The roots lying directly below the surface of the earth can be protected with a coconut mat. It is also recommended to place a felt mat or bubble wrap around the pot. Alternatively, you can also use a jute bag to place the pot in.
To prevent moisture and cold from penetrating, it is also recommended to place a Styrofoam or wooden plate under the pot. Finally, the above-ground plant parts are protected with a fleece.
Plant bags are much easier to use. Because of their size, they can easily be used for multiple potted plants. The integrated zipper also makes regular ventilation easier. This is especially necessary on frost-free days to prevent moisture and pests from accumulating. The translucent material still allows enough radiation to reach the plant.
Overwinter planted olives outdoors
Specimens transplanted outdoors are primarily in exposed places that are often extremely vulnerable to the weather. In order to get Olea Europaea through the winter well, good frost protection is required.
How to do it
- Cover tree slice with leaves, brushwood and mulch
- Wrap the trunks of young plants with a reed or coconut mat
- Cover the crown area with fleece
- Air regularly
Alternatively, a portable greenhouse can be built around the olive tree. These are commercially available in various sizes and designs and are characterized by their quick assembly. However, caution is advised when dealing with high snow loads. The high pressure can cause both the greenhouse ceiling and the fleece to give way dangerously. The result is injuries to the olive, which cannot withstand the pressure from above. Even with this form of cultivation, regular ventilation on frost-free days is absolutely necessary. For young seedlings, the casing of the trunk must also be removed. Accumulated moisture can then evaporate so that there is no risk of illness.
Once olive trees have established themselves in the location, in some cases only crown protection is necessary.
Overwinter olive tree indoors
Wintering indoors is also quite popular. Especially in regions that are exposed to severe frosts, it is recommended to move it to a consistently frost-free location. However, only rooms that provide appropriate exposure and temperature are suitable.
Greenhouse and unheated winter garden
The greenhouse and the unheated winter garden already offer ideal conditions for wintering. The glass material ensures sufficient exposure. Despite the microclimate inside, special winter protection for the plants is recommended at temperatures below 0 degrees Celsius. We recommend installing a frost monitor. This emits constant heat over several days, which prevents the tree from falling below the frost line. Temperatures between 5 and 10 degrees Celsius are optimal. At temperatures above 12 degrees Celsius, the olive ends its winter rest. Therefore, check the heat level regularly using a thermostat.
Hallway, garage and cellar
In particular, overwintering in the hallway, garage or basement isnot easily possible Lighting in particular is a problem in the garage and basement. In any case, it should There should therefore be a south or west facing window nearby. While the temperatures in these rooms are often already in the desired zone of 5 to 10 degrees Celsius, interior rooms such as the hallway tend to be too warm. Cool corridors that face north usually hardly heat up, so wintering is possible here too. Separate protection of the plant is not necessary in these locations.
Apartment
Wintering in the apartment is not possible due to the usual temperatures of over 18 degreesThe olive cannot go into hibernation at these temperatures. It therefore requires consistently high light intensity, which cannot be guaranteed, especially in winter. As a result, the tree loses its leaves and eventually dies.
Care in winter
Olea europaea also needs care in the winter months. This is less extensive due to the extended winter dormancy, but is essential for the plant's survival. The following sections will therefore focus in particular on correct irrigation and fertilization.
Watering the olive tree
To prevent the root area from drying out, continuous, moderate watering is advisable when temperatures are above zero. The root ball should never dry out, but should not be too wet either. Persistent waterlogging leads to rot on the root strands. As a result, the entire plant dies. It is therefore advisable to check the moisture of the substrate with a finger test. When the soil has a dry structure at a depth of two to three centimeters, the olive can be watered again.
A watering rhythm of two to three weeks has proven to be a good rule of thumb. The temperature is particularly important for water requirements. The cooler the tree is, the less water is needed.
Fertilize olive tree
Although the olive tree is an evergreen plant, it needsno fertilizer in winter. Constant application of fertilizer can even lead to stress reactions in the plant, which it responds to by leaf fall. Therefore, only fertilize during the growing season from May to August. Due to their limited volume, potted plants need new nutrients more often than planted plants. Regular fertilization every three to four weeks provides the tree with optimal care. You can find tips on correct fertilization during the growth phase in this article.
Winter olive tree
The olive tree can leave its winter quarters as soon as the severe frosts have passed. As a rule, alreadyfrom March only slight temperatures below zero are reached, which can be survived without any problems. The plant should be wintered out at the latest when the temperature limit of 12 degrees Celsius during the day is exceeded.
A much greater danger to the tree is exposure to sunlight in spring. During the winter months, the plant is only used to moderate light. It is therefore advisable to slowly acclimate them to sunlight in spring. In this way, leaf burns are avoided, which can only be eliminated by pruning.
This is how winterization works:
- 1. – 2nd week of winterization: only shady place
- 3. – 4th week of winterization: place in the sun for a few hours, but definitely avoid midday sun
- from the 5th week of hibernation: placement in the desired location in full sun
In addition to wintering, repotting at the same time is advisable. At the latest when the crown diameter exceeds the pot diameter, it is time for a larger planter. In this context, the existing substrate should also be removed as best as possible in order to lay a good foundation for the new growth.
Wintering in early spring can easily be combined with repotting. This gives the olive new space at the beginning of the new growth phase.
Information on correct repotting can be found here.
Diseases and pests
Especially during wintering, the olive tree is susceptible to diseases and pests due to its slowed metabolism. But a lack of care also increases susceptibility.
Frost Damage
Frost damage occurs when the outside temperature temporarily falls below the tolerable outside temperature. For most varieties, this limit is -5 degrees Celsius. Just a few hours below this limit can cause irreparable damage to the plant. Particularly sensitive areas are
- branches
- Cambium (growth layer in which the water and nutrient pathways run) and
- Roots
As a rule, dead areas are only visible once the buds have sprouted. These remain in their original state and may lose their leaves. Before radical pruning, the damaged parts of the plant should be located as precisely as possible. This keeps the stress on the plant at a tolerable level, especially in view of its low tolerance to cutting and slow growth.
Root damage can only be determined by planting out. Frost damage in this area usually only occurs on potted plants. If the plant shows leaf loss without the shoots showing frostbite, damage to the root area is likely. In this case, repot the entire plant and remove soil from the root ball. Dead root parts can be recognized by their dark discoloration. These should be cut back generously to encourage the formation of new shoots. In combination with fresh, nutrient-rich substrate, minor injuries can heal again.
Pest Infestation
A variety of insects nest between the branches or in the bucket before the onset of winter. Below we have put together an overview of the most common pests with their identifying features. Further information about individual pests and alternative treatment options can be found here.
Aphids: Aphids are difficult to see with the naked eye due to their small body size. The damage manifests itself in a stunting of the leaves as the plant sap is withdrawn from them. As a result, the plant shows overall stunted growth. As a rule, only the eggs in the ground survive the conditions in the winter quarters. However, these hatch in early spring and weaken the olive, which is still growing. Spraying the plants with field horsetail juice is suitable as a preventive measure and also in the event of an acute infestation.
Small Weevil: The Spruce Weevil generally poses no danger to the olive tree. However, the larvae can cause immense damage to the root system. The females lay up to 800 eggs per year directly in the ground. After a three-week rest period, the larvae gradually hatch and begin to eat underground parts of plants. Only next spring will the larvae increasingly pupate and stop feeding. Due to the limited guidance function, the plant becomes very weak overall and is in danger of drying out despite sufficient irrigation. Nematodes that are added to the substrate are particularly effective against the caterpillars.
Scale insects: Scale insects hardly stand out from the leaf structure due to their greenish color. Nevertheless, the insect infestation leaves clearly visible feeding holes and webs near the leaf veins. As a result, the leaves become stunted and eventually fall off. In addition to the adults, the eggs are also completely insensitive to frost, so timely detection and treatment is necessary. Natural control is possible with nettle or wormwood manure, which is sprayed several times.
Mealybugs: Mealybugs can easily survive temperatures down to -40 degrees Celsius. However, the damage pattern differs significantly from that of other pests. In contrast to these, the mealybug secretes a sticky secretion, honeydew, on the infected plants. This is caused by the sucking of plant juices from the ducts. As a result, the leaves turn yellow to brown and eventually fall off. Since the pests do not have adhesive profiles, they can be sprayed off with a powerful jet of water. Alternatively, spraying with a mixture of water and spirit is also promising.
Diseases in winter quarters
In addition to pests that nest on the plant itself or in the soil, pathogens in winter quarters are also a widespread problem. Above all, unfavorable location conditions and incorrect care promote illness.
As soon as the foliage begins to wither despite an adequate supply of water and nutrients, a pest or pathogen is often involved.
Eyespot: Eyespot is characterized by circular spots on the leaves. As the disease progresses, the circles become larger and larger. The result is leaf fall and subsequent branch dieback. The olive has often been infected with the fungus for a long time before the first symptoms become visible. Nevertheless, rapid treatment after the first visual signs appear is important. Otherwise there is a risk of spreading to all surrounding plants. Therefore, remove all parts of the plant that have already been infected as quickly as possible and dispose of them in the trash. The remaining parts of the plant should then be treated with a fungicide.
Fire bacterium: The course of the disease with the fire bacterium often goes unnoticed for a long time. Transmission occurs exclusively through infected insects such as lice and cicadas, which introduce the pathogen directly into the bloodstream. Over several months, the phloem, which is responsible for supplying water and nutrients, becomes clogged, so that the olive gradually withers away. The first signs are dry leaf edges, later the plant becomes completely dehydrated. There is still no known treatment for the disease.
FAQ
What diseases can affect olives in winter quarters?
The most common diseases are eyespot disease and fire bacterium. Transmission occurs either through fungal pores or through host insects that place the pathogens directly on or in the plant.
What does frost damage look like on an olive?
Frost damage is often not visible to the naked eye. It is not until the following spring that the affected sections show no new growth and a dead structure. Beforehand, you can only check the activity of the individual branches by making a targeted cut.
How do you overwinter an olive tree?
When overwintering, the focus is on protecting the roots and crown. The roots can be protected with a coconut mat, bark mulch or leaves. These allow for constant ventilation but keep the area frost-free. The tree crown should be wrapped with an air- and light-permeable fleece, preferably with several plants together.
When does an olive tree overwinter?
The most common species in our country can tolerate temperatures down to -5 degrees Celsius. Even just a few hours of lower temperatures can cause irreparable damage to the olive. The move to winter quarters should therefore take place at night at the latest if this limit is not reached. As soon as there are no longer any plus temperatures in sight during the day, a permanent transfer to a suitable location makes sense.