Tips and edges turn brown and soft rather than dry and papery, and the soil stays damp for days.
Damaged roots can’t supply the leaf tips.
The fix
1
Let the soil dry out and water again only once the top 5 cm (2 in) of soil feel dry.
2
If the base is soft or the roots are brown and mushy, unpot it, trim the soft roots, and repot in fresh, fast-draining mix.
3
Wear gloves and eye protection before cutting or dividing.
More about this
The milky latex can irritate skin and seriously harm eyes, and the stems have sharp spines. Avoid contact with the sap and wash your hands after handling. Keep cut pieces away from children and pets.
Other possible causes
Not a match? Compare the signs below to find the one you have.
Too much direct sun
Dry brown patches or scorched edges show up where strong sun hits the leaf.
How to tell
Crown of thorns wants bright light and some direct sun.
The fix
1
Filter the harshest midday sun with a sheer curtain for a few weeks, then reintroduce the sunny spot gradually so the leaves can harden off.
Tap-water minerals and salts (a smaller factor here)
Crown of thorns tolerates tap-water minerals better than more sensitive foliage plants (calatheas, prayer plants), so this is rarely the main cause.
How to tell
Salts can still build up in a mix that’s never flushed, though.
The fix
1
If tips keep browning despite correct watering, flush the mix thoroughly with plain water every few months to clear any accumulated salts.
Fertilizer burn (easy to cause on this plant)
Tips brown within a week or two of a feed.
How to tell
Crown of thorns needs so little feeding that a normal houseplant dose is often already too strong for it.
The fix
1
Flush thoroughly with plain water, then feed at half the recommended strength and about every 30 days while it’s actively growing.
Dry heat from a radiator or vent
Tips brown mainly on the side facing a radiator or heater vent.
How to tell
Crown of thorns does well at 30–50% humidity, so ordinary room air is rarely the cause on its own.
The fix
1
Move it away from the heat source.
More about this
It doesn’t need misting or a humidity tray.
Occasional dry spells (a minor factor here)
Because crown of thorns goes long stretches between waterings by design, the very oldest leaf tips can dry and brown even with correct care.
The fix
1
Water according to moisture, only when the top 5 cm (2 in) of soil feel dry.
2
Check drainage and do not add water just because a tip is brown or a calendar says it is time.
More about this
This is a much smaller factor than on thirstier plants and rarely the main cause.
