Lynn Dibley on how to help your houseplants stay in tip-top condition in winter
Reduce watering and trim back excess growth to keep them tip-top
As most plants depend on sunshine for energy, they start to shut down in autumn to conserve energy during the darker winter months. Large plants which during the summer months would have needed watering daily, now only need a light watering once a week or fortnightly, depending on the average temperatures they’re growing at.
Evergreen plants shed their older leaves during autumn, which is why you can end up with bare stems and only healthy young leaves clustered at the tips. This is especially true with the taller-growing cane begonias, such as ‘Little Brother
Montgomery’ and ’Lucerna’, or the taller impatiens, such as Impatiens
niamniamensis. If left uncut these plants will get taller year by year but they become ungainly. It may seem drastic, but I like to cut back cane begonias and impatiens in the autumn, ready for the young growth in spring. This young growth will come from the base of the plant and helps to create a denser and more compact, stronger plant.
When cutting a cane begonia down in the autumn, position the plant on a table or bench at waist height so you can stand back every few minutes and check that the final shape is going to be uniform. With a multi-stemmed begonia, after removing a few stems I’ll turn the plant before removing the next few stems and continue cutting and turning until I’m happy with the result. ‘Little Brother Montgomery’ will have many young shoots at its base and it’s this young growth which I’m relying on for next year’s new stems. Start by removing the older bent or twisted canes and those that are elongated. ‘Lucerna’ generally has fewer stems so it’s best to only remove about a third of them, cutting the stem above a leaf which has a bud for a shoot in its axil. Begonia sutherlandii dies back for the winter. It’s native to the mountainous woodlands of South Africa and often grows alongside wild Streptocarpus gardenii, on stream banks. During the summer months these two plants need the same care but in the autumn streptocarpus keep their leaves while B. sutherlandii will die off completely above ground. As the days shorten, the stems of B. sutherlandii gradually all drop off and you’ll be left with a tuber in the compost; during this process stop watering. If you’re lucky the plant will have produced little bulbils in all the leaf axils, which, if collected, can be sown next spring to produce masses of new plants. Keep the tuber and bulbils dry and frost free during the winter.
Achimenes (hot water plants) and kohleria are also plants which die back completely in the autumn and leave rhizomes in the compost. These rhizomes are formed from the roots and are a water and food reserve with the ability to produce new shoots when conditions are favourable. Achimenes produce short rhizomes, 1-4cm (⅜-1½in) in length, while kohleria rhizomes can be up to 40cm (16in) in length. In spring break the kohleria rhizome into 2½-4cm (1-1½in) sections and use about seven pieces in a 12cm (5in) diameter pot.
Plants which form a crown of leaves in a rosette shape often discard their older outer leaves, streptocarpus and saintpaulias (African violets) are prime examples of this type. Streptocarpus leaves also draw their energy away from the distal ends (the oldest section) of leaf, forming a narrow, yellow, transverse line (abscission line) across the leaf. The furthest section of leaf turns pale and will eventually drop off. You can hasten the tidy up by removing the section of leaf above the abscission line as soon as it appears. cactus) will need to be positioned out of cold draughts and kept to a careful watering regime where they never dry out excessively, otherwise either of these problems can lead to flower buds dropping.
Cut back the longest and any bent stems on cane begonias
Begonia ‘Lucerna’ doesn’t need such a severe trim
Abscission lines in a streptocarpus leaf
Begonia sutherlandii will die back to tubers
Keep cyclamen in good light and water sparingly
After a long growing season kohleria pots can be completely full of rhizomes
The growth on Impatiens niamniamensis
can become ungainly if left unchecked
Keep your Christmas cactus out of cold draughts