Yes, cold draughts and hot radiator air are both genuinely harmful to tropical houseplants, though in different ways and to different degrees. Cold draughts cause rapid localised cell damage to leaf surfaces, producing brown blotches, sudden leaf drop, or wilting in the affected area, often within hours of exposure. Radiators produce warm dry air that rises past nearby plants, dramatically lowering the relative humidity in their immediate environment, which causes brown leaf tips, leaf curl, and increased spider mite pressure. Neither problem requires removing the plant from a heated room entirely; it requires placing plants away from the direct air flow of both draughts and radiators.
How Cold Draughts Damage Plants
Tropical houseplants evolved in relatively stable, warm, humid environments. Their cell membranes and biochemical processes are not adapted to sudden temperature drops, and a cold draught from an opening door, a gap in a window seal, or a letterbox causes rapid chilling of the exposed leaf surface. The cells contract faster than the surrounding tissue and the cell membranes are damaged, producing brown blotches (similar in appearance to scorch) or wet-looking collapsed patches on the affected areas within hours. The pattern typically corresponds to the part of the plant closest to the draught source.
Cold draught damage is most severe in winter when the outdoor air coming through doors and windows is very cold. The plants most sensitive are humidity-loving tropical species: Calatheas, Anthuriums, and many orchids show cold draught damage quickly. Sansevierias, Pothos, and Dracaenas are more tolerant. Position vulnerable plants away from exterior doors that open frequently and from window gaps.
How Radiators Affect Plants
Radiators do not burn plants (unless the plant is in direct contact with a very hot surface). The problem is the dry air they produce. Heated air rises from the radiator and carries very low-humidity air upward and outward. A plant positioned directly above a radiator (on a shelf, for example) or immediately beside one is bathed in air that may be 20 to 30 percent relative humidity during peak heating, significantly below the 40 to 60 percent most tropical plants prefer. The result is progressive brown leaf tips, leaf curl, and accelerated transpiration that the roots may not keep up with, leading to drought stress even with adequate watering.
A pebble tray of Expanded Clay Pebbles under a plant near (but not directly above) a radiator provides useful compensatory humidity through evaporation. A position a metre or more to the side of a radiator, rather than directly above it, also significantly reduces the dry air impact. See our guide on what humidity houseplants prefer for target levels and how to achieve them.
Identifying Draught vs Radiator Damage
Cold draught damage typically appears as sudden, sharply defined brown patches or sudden leaf drop, often after a cold day when doors or windows were opened more than usual. Radiator-related damage appears as gradual brown tips and curling edges that worsen through the heating season (winter) and improve in summer when heating is off. The location of the damage on the plant also differs: draught damage affects the side of the plant facing the draught source; radiator damage tends to be most pronounced on the leaves highest on the plant (closest to the rising warm air).
Related Questions Worth Knowing
Can I keep plants on a windowsill with a radiator below it? This is one of the most common plant positions in UK homes and one of the most problematic. The radiator below heats the air rising around the pot, the window glass may be cold at night, and draughts from the window can affect the plant. For a windowsill above a radiator, only the most tolerant plants (Sansevierias, ZZ Plants, succulents) cope well. For Calatheas, Ferns, and other humidity-sensitive plants, this position is genuinely harmful and should be avoided. A pebble tray helps, but a different position is preferable for sensitive species.
My plant is dropping leaves and I can't work out why. Could it be a draught? Sudden leaf drop (more than two or three leaves at once) in a plant that was previously stable is often triggered by a change in environment: a new position, a cold draught from a recently-opened window, or a night where the heating was off and temperatures dropped. Check whether the timing of the leaf drop coincides with a change in conditions. See our guide on why houseplants lose leaves for a diagnostic approach.
Are all houseplants equally affected by draughts? No. Succulents, cacti, and plants from more climatically variable environments (many Mediterranean and temperate species) are generally more tolerant of draughts and temperature fluctuation. Tropical forest species, particularly those from equatorial environments, are the most sensitive. Fiddle-leaf Figs (Ficus lyrata) are well known for dramatic leaf drop in response to even minor draught exposure. Calatheas, Anthuriums, and Marantas are similarly sensitive.