As daylight shortens in autumn, how do I move houseplants closer to a window without scorching them?

Move them in stages, not in one step. A leaf that has spent the summer two metres back from the glass has built a cuticle and a photosynthetic apparatus tuned to that light level. Drop it straight onto a south-facing sill and the excess photons go into photo-oxidative damage rather than sugar — you get bleached, papery patches within two or three days, and those patches never recover.

A workable schedule is to halve the remaining distance every three days. A plant two metres from the window goes to one metre, then fifty centimetres, then onto the sill over roughly nine days. That gives the plant time to adjust chlorophyll density and build up the xanthophyll cycle pigments that dissipate surplus light as heat.

Watch the newest fully expanded leaf, not the oldest. Older leaves acclimate poorly and may yellow regardless; the new growth tells you whether the plant is actually coping. Reddening or a silvery cast on new leaves means you moved too fast — pull back one stage and hold for a week.

Two things change the maths. South-facing glass in winter delivers far more direct light than the same window in June, because the sun sits lower and shines further into the room — so autumn is exactly when sunburn happens, counterintuitively. And clean glass transmits noticeably more light than glass with a season of dust on it; if you wash the windows on the same day you move the plants, you have made two changes at once.

For thin-leaved tropicals such as calathea, maranta and most ferns, stop one stage short of the sill entirely. They evolved under canopy and will scorch in direct winter sun no matter how gradual the transition.