Lemons, tangerines and their warmth-loving relatives are not made for the frosty winters of central Europe. But if a few points are observed when choosing a location and caring for it, it is also possible to overwinter citrus plants successfully in more northern regions.
When temperatures approach zero degrees, citrus plants should move to their winter quarters. Here we tell you what you should pay attention to when choosing the location and whether wintering outdoors is also an option. To ensure that your citrus tree gets through the winter safely, we also explain all the important care measures that ensure a he althy plant in spring.
Which citrus plants are hardy?
Almost all citrus plants such as Lemon (Citrus x lemon), Orange (Citrus sinensis ) and tangerines (Citrus reticulata) only survive temperatures down to around - 5 °C.
However, some hardy citrus plants are so hardy:
- The three-leaf orange (Poncirus trifoliata) can withstand temperatures down to - 25 °C
- The Ichang lemon (Citrus ichangensis) is frost tolerant down to - 15 °C
- Kumquat (Citrus japonica) can handle temperatures as low as -12 °C
These and other representatives of the conditionally hardy citrus plants are often crossed with less tolerant species in order to obtain more frost-tolerant varieties. When buying a citrus plant, you should therefore seek competent advice on frost hardiness. If you are not sure which hybrid is in your citrus tree, you should play it safe and overwinter in a frost-free location.
Important: The hardiness of citrus plants also depends on care. If you fertilize too late, too much or with the wrong nutrient, winter hardiness can suffer. It also causes too much watering and cutting the citrus plants too latesusceptible to frost. Older plants are generally more frost hardy than young ones. In addition, due to regional and local temperature differences, citrus trees can safely overwinter in one home garden, but freeze in a less sheltered garden nearby because wind and humidity damage them. It is therefore important to always play it safe when wintering the Mediterranean plants.
If your citrus plant is an orange or lemon tree, we also recommend our special articles on wintering orange trees and wintering lemon trees.
Citrus plants overwinter
Citrus plants overwinter optimally in cool temperatures in a bright place. Even if you don't have such a place to overwinter your citrus tree, you can keep your plant he althy through the cold season. The most important rule of thumb when choosing a location is: The cooler the place, the darker it can be and the brighter the place, the warmer it can be.
The following also applies to all citrus plants: as long as the temperatures allow, they should stay outdoors. There they get a maximum amount of light and pests cannot spread so quickly. A wind-protected place on a sunny house wall is generally ideal for citrus fruits and especially for the transitional period. The wall warms up during the day and releases the stored heat at night - these are the conditions that Mediterranean plants love.
Citrus plants generally tolerate light and short-term frosts down to - 5 °C and can even prevent pest infestation during the hibernation. So it is important to keep an eye on the weather. The citrus plants should move to their winter quarters at the latest when the temperatures continue to drop or periods of permafrost are announced. Depending on the region, this is the case between the end of September and the end of November. It should be noted here that the temperatures locally, i.e. in your own garden or on the balcony, often deviate greatly from the forecast. It is therefore better to rely on your own experience and the thermometer than on the weather forecast.
Important: Citrus plants are sensitive to relocation. Moving or turning several times means great stress for the plant and should be avoided, otherwise leaf fall can occur.
Hint: Greatest enemy of the MediterraneanAutumn is too wet for citrus plants, because a damp root ball reduces frost hardiness. It is therefore important to choose a permeable substrate that does not get waterlogged - conventional peat substrates are unsuitable here. Our Plantura organic potting soil is more suitable, which is particularly permeable due to its expanded clay content and can therefore promote the winter hardiness of citrus plants. In the bucket, the organic soil can also be mixed with more expanded clay or other coarser stone material so that it remains structurally stable and well drained for a long time.
Winter citrus plants outdoors
Overwintering outdoors can only be considered for citrus species with a particularly pronounced frost tolerance.
Greenhouses, sheds or garages with a natural light source are suitable for wintering outside. An orangery - there are also mobile variants - offers citrus fruits an optimal place to overwinter. However, this purchase is associated with corresponding costs. In order to rule out temperatures that are too cold, a frost monitor or the use of frost protection candles is also worth considering. Jute or bast mats are suitable for additional protection of the root ball. You can use a roasting thermometer to check the temperature in the pan. If the ground in the wintering place is particularly cold, you can warm the feet of the citrus plant with an insulating styrofoam plate or an electric blanket. Check out our special article for more tips on how to protect plants from frost.
Tip: Some service providers also offer winter storage under optimal conditions in orangeries - collection, plant protection on site and return transport to you are often included in the service.
Important: protect citrus plants from frost
If it gets really icy outside, the temperatures can fall below freezing even in the winter quarters, depending on the insulation. Use an electric frost monitor that heats up when the temperature falls below a critical level to prevent damage to the plants. An alternative are frost protection candles, which can increase the temperature in the winter quarters by a maximum of 2 - 3 °C when severe frost is announced. With this method, however, it is important to keep a close eye on the weather forecast.
Wintering indoors
The citrus trees can optimally overwinter at temperatures that are as cool as possible between 1 °C and 12 °C in a bright place. The metabolism is shut down in acold sleep mode. Such cool conditions can be provided by unheated rooms, garages with daylight and conservatories. Staircases can also be suitable, provided the plant is not exposed to drafts there.
If such a place is not available for wintering, a warmer, very bright interior can also be chosen. Here the citrus tree does not go into a dormant phase, but continues to grow slowly. If the plant overwinters at room temperature, there is not enough light indoors to enable sufficient photosynthesis. Double glazing and sun protection glazing often means that the plant does not get enough usable light, even in relatively bright rooms. During a warm hibernation, the entire crown should therefore be illuminated by one or more plant lamps with around 100 watts. Metal halide vapor lamps or fluorescent tubes are suitable because they emit wavelengths that can be used for photosynthesis.
Tip: When do citrus plants shed their leaves?
- If the plant is moved and rotated frequently.
- If the hibernation location is warm but too dark: The light supply is not sufficient to gain energy in photosynthesis. Due to the warm and often dry air, however, the plant has to carry out a lot of energy-intensive cell respiration. As a result of this undersupply, the citrus tree sheds leaves to save energy.
- If the wintering place is cold but very bright: The brightness makes the plant do a lot of photosynthesis. The cold, however, makes the processes for absorbing and transporting water and nutrients in the plant very slow. As a result of this undersupply, the leaves are shed to slow down the rate of photosynthesis.
The right care in winter quarters
The hibernation phase is just as dangerous for citrus plants as general anesthesia is for us humans - so you should keep a close eye on the saplings.
Check for pests
During the hibernation, many pests find optimal conditions to spread and also infest neighboring plants. To avoid damage, it is important to check for typical pests before and during winter storage. See our special articles for tips on controlling scale insects, spider mites and mealybugs.
Fertilize correctly
In cool hibernation, the last fertilizer application of the year in October is recommended. Citrus plants should not be fertilized between November and March so as not to disturb the dormant phase. If the winter is bright and warm with lighting, it makes sense to fertilize once a month, otherwise a lack of nutrients is inevitable. It is best to use a primarily organic liquid fertilizer with trace elements, such as our Plantura Organic Citrus & Mediterranean Fertilizer. This is precisely tailored to the needs of citrus plants and contains all the important nutrients.
Water in winter quarters
The plant should be watered as needed, i.e. when the substrate is dry, with water at room temperature and with as little lime as possible. Plants that have wintered in a warm environment use and naturally need water much more frequently. Spraying the leaves with boiled water every two to three days can counteract excessive leaf shedding. Regular airing, but without a strong draft, is also important.
Winter out citrus plants
The following applies to hibernation: As soon as the temperatures allow, a citrus plant wants to be outside again. It could be from April, but the weather forecast should be closely monitored and winter protection material should be kept ready until the ice saints in mid-May. With the start of the new growth period from March or April, fertilizer should be applied regularly again in order to provide the plant with the best possible care and to stimulate the formation of new shoots. A primarily organic liquid fertilizer with a nutrient ratio specially tailored to citrus plants is ideal for this. Our Plantura organic citrus & Mediterranean fertilizer, for example, optimally supplies your citrus plant with nutrients and, with additional iron, prevents chlorosis - the yellowing of leaves. The organic fertilizer is safe for pets and garden animals and is simply added to the irrigation water.
After hibernation is the best time to repot citrus plants. Read our special article on what to look out for when repotting a lemon tree.