Nowadays, with our centrally heated houses, it is difficult for us to imagine the struggle houseplants must have had surviving the winter in grandmother’s day. Yet although modern homes present greater opportunities for indoor cultivation, we still often make life much more difficult for our houseplants that it need be. There are often very warm and ice-cold rooms in one and the same house. And at the night when the heating is turned down, or off, the temperature around the windowsill, where most of air plants stand, drops dramatically. Casually, we simply expect them to get used to it.
The first problems arise with the transition from outdoors to indoors. Plants that have spent the summer in the garden, or on a balcony or patio, usually find themselves suddenly whisked indoors. As soon as night frost is in the air, they are rushed into the house again, giving them no chance to acclimatise slowly to their new environment. One minute they are in the fresh air and the next on the windowsill of a warm room. It is wonder they are survive this traumatic change, if at all possible, you should first bring them into a sunny but unheated room which can be ventilated daily.
Most of the plants returning from their summer sojourn will find it is easier to readjust to life indoors at a temperature of 10-15 degrees Celsius. Other norms apply for the so-called greenhouse plants that spend the summer outdoors in tub or plant-troughs, and because of their limited winter hardiness require a cool but frost-free overwintering; the conservatory or cool greenhouse answered this need in formers day. A temperature of 5-8 degrees Celsius is sufficient for Nerium Oleander, Agapanthus, Agave Americana, Citrus species, Laurels, Pomegranates, Camellia, Lantana, and most fuchsias.
Delicate and special cultivated varieties feel happier during the winter at 10 degrees Celsius. ‘Conservatory plants ‘ generally only need a soil watering once a week. Other plants, that spend their dormant period in a rather warmer environment, must be carefully carefully checked foe leaf-fall, this probably means that the atmosphere is too dry. Such is often the case with azaleas. It is therefore recommended that you spray these every day over the crown until the buds begin to color.
Overwintering plants must never be watered if the soil still feels moist and is dark in color. Most cacti, with exception of the leaf cacti, can manage entirely without water between November and March at a maximum temperature of 10 degrees Celsius. It is a fact that in a cool environment most plants die from too much rather than too little water. Plants that shed their foliage in the autumn can also overwinter without water, such as Achimenes, Sinningia (Gloxinia), Rechsteineria (Gesneria), and Hippeastrum (Amaryllis). The temperature for these plants must definitely not fall below 6 degrees Celsius, although a higher temperature is better.
Garden Geraniums (Pelargonium Zonale) are often kept in a cellar or attic during the winter. They are usually the first plants to suffer from frost, and in order to prevent frost damage generally, protect your plants with newspaper at night and remember that even in a heat room the air behind the windows can still be icy cold. So never leave plants on a windowsill behind close curtains. During a period of frost plants standing in an unheated room should not be watered, as a wet root-ball can freeze in no time.
Authors: A. C. Muller-Idzerda, Elisabeth de Lestrieux, Jonneke Krans