Wax begonias are often used as bedding plants, and frequently gardeners prefer to purchase them already-growing from a garden center. However, you can grow wax begonias from a seed as long as you understand the plant's germination and life cycle. If you are going to grow wax begonias, make sure that you have all the right equipment and start well in advance of when you hope to actually use the flowers in your garden.
Get the pot ready for planting. Fill it nearly full of the sterile planting mix and dampen the soil. If it gets too soggy, then let it air out for a few hours to a day so that the soil is damp but not muddy. The soil should have a pH of 6 to 8.
Plant the seeds 4 to 6 months before the last spring frost date. You should push them into the soil, but do not cover them up since they will not germinate without sunlight.
Place the glass plate over the top of the pot. The plants should spend most of their day in full sun, and the temperature of the seeds should not drop below 70 degrees Fahrenheit. The plate will keep the air in the pot humid. The seeds should germinate in 14 to 20 days.
Water the plants whenever the top layer of soil is dry. Make sure that your pots are draining correctly or the plants will rot.
Pinch off blooms to keep your wax begonia blooming. Even indoors, it may not bloom past the first frost. Once the seedlings are at least 10 centimeters tall and nighttime temperatures are remaining consistently above 50 degrees Fahrenheit, you can move your wax begonias outside if you wish.