Most tropical houseplants do not go fully dormant in winter the way outdoor deciduous plants do, but they significantly reduce their rate of growth from October through February. Day length drops to around 8 hours in the UK by December, and light intensity is roughly a third of its summer peak. Under these conditions, tropical plants slow their metabolism, stop producing new leaves, and use very little water or nutrients. This is a normal and healthy response to seasonal change, not a sign that something is wrong. The practical consequences are that you should reduce watering, stop fertilising, and avoid repotting through this period.
What Actually Changes in Winter
The term dormancy is used loosely for houseplants. True dormancy, in the botanical sense, means the plant has entered a metabolically suspended state triggered by cold and short days, as seen in deciduous trees or spring bulbs. Most common tropical houseplants do not do this. A Monstera or Calathea in a heated UK room in January is still alive and metabolically active; it is simply growing very slowly because the light available is insufficient to support fast growth.
The practical difference matters for care. Because the plant is still functioning (just slowly), it still needs some water when the compost dries out, and it still benefits from adequate light. It does not benefit from fertilising or disturbing the root zone.
Which Houseplants go Dormant?
Some houseplants do have a genuine dormancy period involving the die-back of above-ground growth. Tuberous plants like Caladiums lose their leaves entirely in autumn and spend winter as dormant tubers in dry soil. Deciduous ferns lose their fronds. Certain bulbous plants like Oxalis triangularis go dormant when stressed.
These are genuine dormancy events where the above-ground plant disappears and regrows from the tuber or bulb in spring. If your Caladium has suddenly lost all its leaves, this is normal seasonal behaviour, not death.
How to Adjust Care Through Winter
During the slow-growth period (October to February), adjust care in three main ways. First, reduce watering frequency: with growth slowed, the plant uses far less water, and the risk of root rot from wet compost is higher than in summer. Check the compost before watering and let it dry out more than you would in summer. Second, stop fertilising entirely: unused fertiliser salts accumulate in the compost and can damage roots. Resume feeding in March when growth picks up. Third, do not repot as disturbing roots when the plant is not actively growing extends recovery time and provides no benefit.
If you want to maintain summer-level growth through winter, supplemental lighting can make a significant difference. A grow light above the plant compensates for the reduced day length and light intensity.