From late August the daylight your plants receive falls fast — by mid-October a UK windowsill gets less than half the light it did in June. Plants respond by slowing their growth, and some yellowing and leaf loss is a normal part of that.
The problem is that the most common autumn killer — overwatering — produces almost identical early symptoms. Here's how to tell them apart.
Quick symptom checker
One or two old, lowest leaves yellow slowly, evenly, then drop = seasonal slowdown (normal)
Several leaves yellow at once, soil still damp days after watering = overwatering
Yellowing with soft, translucent or mushy patches = root rot has started
Sudden drop of green leaves after a position change or cold draught = shock, not water
Crispy brown edges, curling, very dry soil = underwatering or dry heated air
Cause 1 — Natural seasonal slowdown
In shorter days a plant cannot photosynthesise enough to support all its summer foliage, so it sheds its oldest, least efficient leaves and holds resources for winter.
How to confirm it: the affected leaves are always the oldest and lowest. They yellow gradually and uniformly over a week or more. New growth has slowed or stopped, but stems are firm and the rest of the plant looks healthy. Soil is drying at a normal rate.
What to do: nothing, except adjust care for the season. Remove leaves once they've yellowed fully. Expect one or two a month through autumn.
Cause 2 — Overwatering on a summer schedule
This is the big one. A plant that needed water twice a week in July might need it once a fortnight in October. Keep to the summer routine and the soil never dries, roots sit wet, and they suffocate.
How to confirm it: push a finger 5cm into the soil. If it's still wet or cold more than 5–7 days after watering, you're watering too often. Multiple leaves — not just the oldest — are yellowing, sometimes with brown spots ringed in yellow. The soil may smell sour.
How to fix it:
- Stop watering until the top third of the pot is dry.
- Move the plant to your brightest available spot to help it use up soil moisture.
- Empty any water sitting in the saucer or cover pot — always, every time.
- From now on, water by checking the soil, never by the calendar.
Cause 3 — Root rot (overwatering that's gone further)
If overwatering has been going on for weeks, the roots may already be rotting.
How to confirm it: slide the plant out of its pot. Healthy roots are firm and white or pale tan. Rotten roots are brown or black, soft, and pull apart or smell.
How to fix it: trim away every soft, dark root with sterile scissors. Repot into fresh, free-draining compost — mix in about one-third perlite. Use a pot only slightly bigger than the remaining rootball. Don't water for 5–7 days, then sparingly. Keep it warm and bright while it recovers.
Cause 4 — Shock from a position or temperature change
Moving a plant, or a cold draught from an opened window or an outside door, can trigger a fast drop of otherwise green, healthy leaves.
How to confirm it: the drop happened within a few days of a change. Leaves that fall are still green or only slightly yellow. Soil moisture and roots are normal.
How to fix it: settle the plant in one stable spot away from draughts and radiators, keep care consistent, and wait. It will adjust and push new growth once light improves.
The rule that prevents most autumn losses
Through autumn and winter, water every plant by feel, not by schedule — and always tip away standing water. Roughly halve how often you water compared with summer, stop feeding until spring, and hold off on repotting. Most "my plant is dying" messages in October are simply summer care applied to a winter plant.
Get a definite answer
Photograph the affected leaves and the whole plant, and PlantMedic will tell you which of these it is — with a confidence score, a severity rating and the exact steps to fix it. Free, no account needed.