Maryland Grows

Q:  I have an aloe indoors that is developing some yellow leaves. Do I need to feed it or change something else about how I take care of it?

A:  Leaf yellowing is a difficult symptom to trace back to a particular issue since in general it can be caused by overwatering, under-watering, under-fertilization, too little light, too much light, pest feeding, and a few other factors. With indoor succulents, too much light is a rare problem, and accidental over-watering is relatively common, which is why I presume low light and soil moisture are the conditions needing evaluation first.

A leaf that turns yellow is one a plant is probably about to shed, so even if the original issue is resolved, be aware that it won’t usually green up again. That’s okay, as long as the shedding isn’t excessive (and if it is, it might be too late to fix); plants can reabsorb some of the resources stored in the leaf before it dies and falls. It’s also perfectly normal for any plant to shed its oldest leaves from time to time since they have limited usefulness to the plant as they age or succumb to cumulative injuries or stresses.

Succulents like aloe thrive in bright light while indoors, so it’s possible yellowing has begun because the plant is running low on stored energy that has allowed it to tolerate insufficient light so far. (Plants make their food from light, so while occasional fertilization can supplement their nutrition, it’s not a substitute for receiving enough light.) While indoors, aloe grows best where it gets either several hours of direct sunlight close to a window or is placed under plant grow lights that can supplement or replace natural light (if window light is insufficient).

Succulent roots should get fairly dry between waterings, though each watering still needs to be thorough so all of the potting mix is well-moistened each time to eliminate dry pockets. Extra water should freely drip out of the bottom drain holes of the pot. Feel the soil about an inch deep (or more, depending on pot size) and only water when it’s become pretty dry to the touch at that depth. Be sure to empty any drained water in a saucer promptly so the pot doesn’t sit in water, as this can kill roots. Root rot can result in leaf yellowing because there are not enough healthy roots left to support all of the plant’s foliage. As with other triggers for shedding, the oldest, lower leaves are usually sacrificed first.

If you haven’t fertilized the plant in several months, it might benefit from a light dose. Normally indoor plants don’t need fertilization during the fall through winter, but if a plant has been nutrient-deprived for a while, it may benefit from replenishing those nutrients in the soil. The precise fertilizer formulation doesn’t matter much in this case, though nitrogen is likely the nutrient of greatest importance (the N in N-P-K ratios) for overall plant health and leaf color, so it can be chosen as the highest number of the three (such as 3-1-2 or 10-5-5 as arbitrary examples). Regardless of the type of fertilizer chosen, follow package instructions about how to dose it. You’d probably only need one dose (maybe at most two) to last the plant through the winter since it won’t exhaust those nutrients quickly. If you suspect scale, mealybugs, thrips, or mites are causing damage, get them under control first, since you don’t want to feed the pests extra nutrients with the fertilization.

Indoor plants grow slowly (if at all) in winter, and succulents tend to be slow growers in general, so it may take some time for the aloe to show any improvement, which is fine as long as it isn’t declining further in the meantime.

By Miri Talabac, Horticulturist, University of Maryland Extension Home & Garden Information Center. Miri writes the Garden Q&A for The Baltimore Sun and Washington Gardener Magazine. Read more by Miri.

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