First of all, let’s see what begonias need to live happyly in your house.
Light is a crucial condition. Your begonia would like a southwestern or southeastern window without direct exposure to sunrays – attention to possible sunburns on her leaves!
Another critical point is water. In general terms, begonia likes humid air, but not the soil. It is likely to get ill in air-conditioned or south-exposed apartment where the air is too dry, or if you overwater it. The soil must dry a bit between two irrigations. This plant likes to take shower – you can water it in drops directly on the leaves, and for some species, even on the flowers. Misting begonias daily will make them happy, so does a humidifier.
Pots and soil mixes
Your success with begonia largely depends on the pot and soil mix used. Begonias aren’t fans of overwatering and overpotting. If the pot is too large, any of your small errors in handling begonia can kill her. This is almost impossible, if your plant is under-potted. Move your begonia in a larger pot only when the current one is filled with the roots. If you see that the soil of a certain plant seems to never dry out, may be, its pot is too large.
As for soil, the best for begonias is a soilless mix, composed of peat moss with a bit of perlite granules (2/3 of peat moss for 1/3 of perlite for a perfect begonia mix). Don’t use garden soil, manure or leaf mold. Your mix stays too wet, and this provokes diseases.
Think of regular fertilization of your plant. The frequency depends upon the type of the fertilizer, so read the instructions carefully.
If you want your begonia to flourish all the year round, you’d better know the most common handling problems people face with this plant.
The leaves of your begonia roll. Overwatering of deficient nourishment may be the reason. The soil must be neither soggy nor overdry.
The flowers of a begonia turn dark and fall down. Drops of water that fell on flower buds can be the reason.
The flowers and leaves of a begonia fall off. Several reasons are possible: the air of the room is very dry, your begonia is not moistured enough, or the water has touched the plant.
A begonia doesn’t bloom. Maybe it doesn’t have enough light, the air isn’t humid enough, or it is too warm or too cold in the room. Begonia also hates drafts.
Predators. Red spiders and plant lice are the most common plant aggressors.
Mealy bugs like warm conditions, so good for indoor plants. The best way to get rid of them is plain rubbing alcohol. Use an artist brush sopped in the alcohol, or spray the whole plant with the alcohol from a spray bottle. It’s harmless for the plant.
Major begonia illnesses
The common diseases of begonia are grey mold (botrytis), bacterial and ring spots.
Greyish humid fur spots on the leaves, flowers and top sprouts of begonia can be caused by grey mold. At the beginning you can treat it with Bordeaux mixture or soap-copper solution. If it progresses, spray begonia with 1% benomyl.
Bacterial spot disease manifests as small glassy spots on underside of the leaves. It has no effective treatment, just pull out the plant and disinfect its soil. The prevention is possible with 5% mixture of copper oxychloride.
Yellow-green stripes on leaves and final necrosis are caused by a ring spot disease. There’s no cure, the sick plant must be removed. To prevent it, be sure that your begonia isn’t attacked by sucking insects as lice, thrips or other virus transmitters.