Yellow Leaves on Your Begonias? 5 Things Gardeners Say You Should Check Right Now
Begonias are a favorite flower of both indoor and outdoor gardeners. Varieties like angel wing begonias and rex begonias make attractive houseplants thanks to their vividly patterned leaves, while wax begonias add cheer to garden beds with colorful blooms. But without the proper care and conditions, begonia leaves can turn yellow, signaling that something isn't right with your plant. The good news is that yellow leaves are your plant's way of communicating that something is wrong. The bad news is that several different factors could be the cause, so you'll need to do some investigating to address the problem. Here's why your begonia leaves may be turning yellow—and the first thing you should check to keep your plant looking healthy. Overwatering In general, the most likely cause of yellow begonia leaves is too much water due to either overwatering, poorly draining soils, or a container without adequate drainage. When your plant's soil remains soggy and saturated, its roots can't take up oxygen properly, leading to chlorosis, or yellowing leaves. Left untreated, overwatering can eventually result in root rot, which can seriously damage or even kill your plant. If your begonia has very wet, soggy soil or is planted in an area with poor drainage, that's likely the cause of its yellow leaves. Cut back on watering outdoor plants if possible. For container begonias, allow the soil to dry out completely before watering again. Going forward, check soil moisture regularly and only water once the top inch or so is dry. Consider repotting your plant in a potting mix that includes plenty of perlite for drainage, and ensure that the pot it's planted in has holes in the bottom. Avoid letting the plant sit in water in its cache pot or drip tray. Lack of Sunlight Begonias that don't receive sufficient sunlight may develop yellow leaves because they're not able to photosynthesize as much due to lack of light, which in turn creates similar conditions to overwatering, as plants use water as they turn sunlight into food. Indoors, begonias need bright, indirect light to thrive. Move container plants closer to the light source. Too Much Sunlight A begonia that's planted in a spot that gets an overabundance of harsh, direct sunlight can suffer from sunburn. The plant may develop pale brown spots on its leaves before slowly turning yellow and falling off. Move indoor or container begonias to a spot out of direct sun but with lots of indirect light. For in-ground plantings, consider installing shade cloth—and plan to seek out begonia varieties with a tolerance for full sun next season. Pest Problems Begonias can fall prey to common plant pests like mites, scale, whiteflies, and mealybugs, as well as slugs and snails when planted outdoors. Pest damage may appear as tiny yellow dots, or patches, or the edges of plant leaves may turn yellow and then brown. Examine your plant's leaves and stems closely for signs of pests, such as flat, oval-shaped brown bumps (scale insects), cottony masses (mealybugs), or sticky honeydew, which can be left behind by these sap-sucking insects as they feed. After quarantining your begonia from the rest of your collection, treat infested plants with horticultural oil or insecticidal soap to remove pests. Cut off any severely damaged leaves, bag them securely, and discard them in the trash to keep them from spreading. Monitor the plant closely and treat again if signs of pests return. Plant Diseases Some plant diseases can cause begonia leaves to turn yellow. Bacterial leaf spot can appear as yellow rings around water-soaked leaf areas, but it can be prevented by keeping the leaves as dry as possible during watering. Cut away damaged plant parts, bag them up, and throw them away—then sterilize your tools to keep from spreading the disease. Viruses can cause pale yellow rings or spots to form on begonia leaves as well. If you suspect a virus is the problem, remove, bag, and discard infected plants to prevent spread.
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