Physiological disorderLeaves

Normal leaf ageing

Not a problem, and included as a candidate because it is one of the commonest explanations for a single yellow leaf on an otherwise healthy plant. Every plant sheds its oldest leaves; a differential that cannot return 'nothing is wrong' will always find something to blame.

What brings it on

The oldest one or two leaves — lowest on the stem, or outermost on a rosette — yellowing and dropping while the rest of the plant grows normally. Also seasonal: many plants shed some leaves in autumn or after flowering.

source

Horticultural consensusmoderate confidence

Royal Horticultural Society: Houseplant problems

Checked 2026-08-13

Preventing it

Ordered by how much difference each measure actually makes, not by how often it is repeated.

Nothing to prevent. Recognising it is the whole point, because a healthy plant treated for a disease it does not have usually ends up with a real one.
source
GrowingHQ editorial positionhigh confidence
Recorded as editorial judgement rather than sourced guidance because it is a framing decision about the differential rather than a horticultural fact.
- GrowingHQ editorial synthesis — GrowingHQ
Checked 2026-08-13

Dealing with it once it is there

Remove the leaf if it looks untidy. Nothing else is required.
source
Horticultural consensusmoderate confidence
- Royal Horticultural Society: Houseplant problems
Checked 2026-08-13

On sprays and treatments

GrowingHQ does not tell anyone what to apply, at what rate, or how often. Pesticide approvals differ by country, change without notice, and the product label is legally binding — it is also the document you are holding. What is described here is cultural and physical control, which is what a home grower can act on without a label in front of them.

Plant-specific guides

Where this is one of several causes that look alike on a particular plant, GrowingHQ publishes the differential rather than the general answer.