I like to say “brown is not sunburn, it’s a stress color” (and stress is not always related to sun exposure), but really there’s a few different reasons why your Aloe may turn brown…it’s not always a stress reaction, and telling the difference between rot, fungus and stress may be difficult for people who haven’t been growing (and killing!) Aloes for over 10 years. It may even be difficult for those who have been growing them a long time, given the rampant misinformation being spread around. The most common (wrong) advice given is brown is sunburn or “too much” sun, but fungus spots can turn your plant brown, and so can rot. Learning to spot the early signs of rotting is definitely tricky, but can be done and if you catch it in time you can save your plant!
Rot is a very common problem people encounter when trying to grow Aloe plants, especially using poor draining soil and not giving it enough light. Weak growth from lack of light makes it much easier to lose a plant to rot. What you want to look for is a clear brown color, that often leaks fluid (or at least has a wet look to it)…the plant is pretty much melting. It usually starts at the roots or in the leaves and stem at the base of the plant or in the center (crown rot) and work it’s way through the stem. If you catch it in time, clean off the rot and have enough healthy stem left you can save your plant. Sometimes it will work it’s way through the stem before you see any signs of rot, unfortunately. Unpot the plant, clean it up and leave it unpotted in a dry place that gets good airflow out of full sun. You might dust some cinnamon on the parts you cut the rot off of. Watch it for a few days to make sure it is done rotting and then repot in a dry, better draining soil mix. Don’t water. If you have to cut roots off, that’s fine. The stem will grow new roots. If you have to cut the center out of the plant, that’s fine too…it will produce new growth from the center as long as there is still healthy tissue. If you have to cut the whole plant back, leaving just a stump and roots…yep, that’s ok too! The stem is the important part…having healthy stem tissue left is where new growth will come from. Catching the rot in time is difficult as it spreads quickly and can easily go undetected. Sometimes a plant will look fine one day and it’ll collapse on itself the next…it happens. It sucks, but it’ll help in the future, especially if you have photos and can look for the signs you might have missed.
Fungus, another common problem that can be caused by poor drainage, overwatering, and/or weakened growth. Usually appears as little brown dots that spread over the leaves of your plant, or larger, round brown spots that kinda sink in. There is one that forms orange-ish rings of fungus as well, fittingly called rust. Despite getting lots of sun and having excellent drainage, some of mine get the big round fungus spots still. It seems most common in the maculate group (maculata and the related species/hybrids) and the perfoliata types (nobilis, mitriformis, T-Rex, distans, brevifolia.) I attribute it to the high humidity, and it mostly happens on the lower leaves that are already starting to die off and don’t get as much air flow. Also, most of the perfoliata types are winter rainfall plants, meaning they don’t really want much water when it’s hot. I have trouble growing those here. Aloe vera is NOT summer dormant, but some Aloes are. That’s another reason it’s important to know the variety of your plant. Not all Aloes want the exact same care.
Bonus – Aloe mites. Sometimes the deformed growth caused by these mites can be brown.
AloeHoarder 