Overwintering exotics like lemon trees is always fraught with difficulties. Since the plants are not native to moderate climate, they often behave stubbornly in the winter quarters. But if you follow a few points, wintering your lemon tree is not a problem at all.
As Mediterranean tub plants, citrus trees are extremely popular. Whether on the balcony or terrace, lemon tree, orange tree, kumquats and lime tree are among the most popular ornamental plants in the tub. But unfortunately, these tropical beauties need warm temperatures and plenty of sun to develop properly. So what to do when the days get shorter in the fall and the first night frosts threaten outside? Put the tree in the garage? Or in the greenhouse? Or perhaps simply in the living room? Lemon trees in particular tend to be petulant during the winter, and time and again trees die in their winter quarters. To prevent this from happening to you, you can read here how to properly overwinter a lemon tree.
Why lemon tree loses its leaves in the winter quarters?
Especially often it can be observed that after a few weeks in the winter quarters lemon trees lose their leaves. This is rarely a care mistake, but most often has to do with undesirable temperature fluctuations. For example, if the tub plant stands in a terracotta pot on a cold stone floor, the roots have cooled down considerably and are in dormant mode. If the sun now shines through the window on the foliage, the upper part of the plant warms up and the leaves are awakened from their winter rest. However, the attempt at photosynthesis fails because the cold roots of the lemon tree do not transport water upwards and the leaves fall off. Thus, the tree dries up, even though you water it. As a result, since the desperate gardener is watering more and more to prevent the tree from drying out, waterlogging occurs and the roots of the lemon tree rot and the tree cannot be saved. The solution to this problem is a clear decision during winterization: if the tree stands cold, then the room must also be correspondingly dark. If the tree stands warm, then the light output must also be correct. Temperature fluctuations in the winter quarters are the biggest enemy of the lemon tree.
Where should you winter a lemon tree?
To get a lemon tree through the winter unscathed, you need the right place. For the reasons mentioned above, overwinter your lemon tree either cool and dark, but not pitch black, or warm and bright. The lemon likes best a cool winter quarter with temperatures between 3 and 13 °C / 37 and 55 °F. It should not get warmer, even if the winter sun shines through the windows. Exception: the special cultivar ‘Kucle’ tolerates winter temperatures up to 18 ºC / 64 °F. A cold greenhouse with slightly shaded windows or a bright garage is optimal. A frost guard protects from sub-zero temperatures. Avoid a too large temperature difference between roots and crown by placing the planter on a Styrofoam or wooden board.
Make sure that any drainage holes in the pot are not blocked. Shade windows where strong sunlight is expected with shade nets so that the winter quarters do not heat up too much, and ventilate regularly.
As an alternative to the cool dark room, the lemon tree can also be overwintered warm. Then it needs temperatures above 20 °C / 68 °F, as they prevail in the living room or a warm conservatory, and as much light as possible, for example, on a patio door or in a bright attic studio. If necessary, you need to help here with additional lighting. In the warm winter quarters, the earth temperature should not drop below 18 °C / 64 °F, otherwise the same leaf fall problem will occur again.
How to care for a lemon tree in the winter?
At the latest when the first night frosts are announced, the lemon tree must move to the winter quarters. Care measures for a lemon tree in the winter quarters depend on the site conditions. If the room is cool and dark, the plant will stop growing and go into dormant mode. Here, only occasional watering is necessary, just enough so that the root ball does not dry out. Do not fertilize the citrus plant over the winter. If, on the other hand, the tree is overwintered in a bright and warm place, it will continue to grow as usual and will then also need appropriate care.
In the bright living room lemon tree is watered throughout the year and also moderately fertilized. Check the lemon tree regularly for pest infestation, because especially in the winter quarters spider mites, scale insects and mealybugs like to spread on the plants. Spray the tree in the warm quarters with low-lime water from time to time to increase humidity, if the indoor air is too dry, the fruit will burst, and ventilate all winter quarters well on frost-free days. In February, the lemon tree can be pruned into shape.
If no more late frosts are to be feared at the end of April/beginning of May, the lemon tree can go outside again. The temperature difference between winter and summer quarters should not exceed 10 °C / 50 °F. Before moving out, young citrus plants should be repotted and given fresh planting substrate. For old trees, just add a little fresh soil to the planter. Slowly accustom the lemon tree to fresh air and do not place it directly in the blazing sun at the beginning, but gradually get it used to more light and sunlight again.