It’s been a while since I’ve grown begonias. There are thousands of varieties, each one prettier than the last one you saw.
Begonias do not like cold weather, keep them from drafty windows in the winter. In October some leaves may yellow and fall off. This is not unusual and if it is just a few leaves not a cause for concern.
Begonias also do not want a lot of sun either. Put them in an northern window or slightly shaded east or west window in the summer months. Put them in a west or southern window during the winter months.
Begonias prefer an acidic soil so put a tablespoon of apple cider vinegar in a gallon of water and use that to water them. They will rot quickly if you over water them. They do not like to be dry either. Water them when the top 1/2″ or so of soil is dry, but also make sure they drain very well. You want a pot with lots of holes in the bottom to drain well so that you can water them often and not have them sitting in water.
Begonias are named after their discoverer, botantist Michel Begon. Begonias are native to the South American mountainous regions. They first reached Europe in the mid-1800s and quickly became popular there as they still are today. Begonias have asymmetrical leaves. Take a close look at all the ones you see.
Watch for mealy bugs, white flies, powdery mildew and scale on begonias.
If your begonia starts looking scraggly give it a bit more light.