Before taking your plants inside, into their winter quarters, clean them properly. Remove all fallen leaves, any withered or diseased foliage, and all dead wood. If there are pests on a plant, you need to treat it before taking the plant in. Never bring plants inside for winter with pests on them.
Then choose a suitable location. Deciduous plants can be put away in a dark place for the winter, but evergreens need light. The warmer the location, the more light the plants need.
Regarding temperature, there are three different categories: Plants which tolerate frost, plants which need to stay frost-free, and plants which need to stay warm over the winter. It is best to keep Mediterranean plants in a light place at temperatures of between 10-12 °C over the winter and to water them moderately so that they don't dry out. Keep tropical plants in a light place at a temperature of 20/22 °C and water appropriately so that they are not too wet but stand in moist soil.
Bring potted plants inside as late as possible and take them out again as early as possible. As a general rule, plants are better off outside than inside, if weather conditions allow it. Since being inside is an abnormal situation for plants, this causes them stress. Angel's trumpets, bougainvilleas, hibiscus and heliotropes, for example, must be protected from frost. Flowering maple, bottle-brush, cassia, citrus, tea-tree and leadwort can withstand freezing temperatures. Mild frost (to approx. -5°C) can be tolerated by hardy plants such as Japanese laurel, Norfolk Island pine, arbutus, Italian cypress, loquat, laurel, olive and Italian maple.
Hygiene in winter grounds
Pot plants need special protection from the cold. In the winter grounds, parasites or fungi could quickly spread. Therefore, hygiene plays a large role in a successful overwintering. Care for your grounds at regular intervals and remove weeds and wilted leaves. Clean up your plants every month. Parasites must immediately be controlled so that they don’t spread to other plants. Check at the end of January for scale fretter and in February, for spider mites, mealy bugs and blade holders which could appear. Standing in cool and moist rooms promotes fungus diseases in tub plants. The plants should therefore stand in an airy place. Tip: on frost-free days, simply air out the room well.
The correct ventilation prevents the growth of fungi. The respective overwintering temperature should be maintained. If so desired, the so-called frost monitor can be installed to ensure that the room does not become too cold. Just as important is to not allow the temperature to get too high which can happen when the days become warmer. Large fluctuations in temperature affect the winter dormancy of the plants and can lead to early budding.