Dry plants will often turn yellow and then brown (even crispy!) at the lower leaves. Over-watering can sometimes present itself in the same way.
Some plants will turn brown and crispy when the surrounding humidity is low or the air in your green space is too dry. This is especially common for plants receiving a lot of direct sunlight or are placed near other sources of heat such as heating ducts or space heaters. If you notice the leaves turning brown and crispy and you suspect humidity may be the culprit, spritz your plant occasionally and move it away from any heat.
Browning Leaf Tips
The tips or ends of leaves may brown due to tainted water, accumulation of salt in the plant’s soil, watering issues (too much or too little), overfeeding, or a combination of these things. Plants with long leaves, such as Peacock Plants, Dracenas, and Spider Plants are especially susceptible to browning leaf tips. Consider your plant’s environment and watering schedule and make changes if necessary. Once you understand what caused the browning tips in the first place, snip off the tips with scissors.
If your plant receives too much fertilizer, you will notice browning around the sides and tips of its leaves. It may also look like it’s very dry. This is because too much fertilizer can actually damage a plant’s roots, preventing them from taking on any water. To correct this, flush your plants to leach out any excess fertilizer.
Pests and Disease
Brown spots in the middle of leaves are often signs of pests or disease. Some of the most common pests affecting indoor plants are spider mites, mealybugs, scale, and aphids. Most pests you can see with the naked eye, but be sure to look out for other signs such as white fuzzy spots, webbing on and under a plant’s leaves, or brown bumps. If your plant has pests of any kind, it is best to dispose of it right away as pests can spread to other nearby plants. If the affected areas are relatively small, you can prune the infected areas or apply insecticidal soap to treat any pest or fungal issues.