How to tell
Dry air (low humidity). Just the very tips and edges go brown and papery while the rest of the leaf is fine. This is most common in winter with the heating on, and Croton prefers 60–80 % humidity.
Tap-water salts (fluoride/chlorine). Sensitive plants (calatheas, dracaenas, spider plants, prayer plants) brown at the tips from minerals in tap water.
Inconsistent or under-watering. The soil dries out hard between waterings, so the tips (the last to get water) crisp first.
Fertilizer burn. Brown tips appear with a white crust on the surface, usually after feeding too often or too strong.
Too much direct sun. Dry brown patches or scorched edges show up where strong sun hits the leaf. Croton does better out of harsh midday sun.
