Fertilizer build-up
Brown tips plus heavy feeding usually means salt build-up in the soil.
Diagnosis
Fertilizer build-up
What's happening
Cast Iron Plant is a slow grower that needs very little food, so it's easy to over-fertilize. Excess fertilizer salts accumulate in the soil and burn the fine root tips, which shows up as browning leaf tips and edges along with a whitish crust on the soil surface.
How to fix it
Flush the pot: run plenty of plain water through the soil until it drains freely, several times over, to wash the built-up salts out. Then cut feeding back hard — a balanced liquid fertilizer at half strength no more than once a month, and only in spring and summer. This plant genuinely prefers to be under-fed than over-fed.
If that doesn't fix it
This is general guidance based on common symptoms; individual plants vary.
Read the full Cast Iron Plant care guide →
Reviewed June 2026 · how we check this