I love non stop begonias but I have noticed mine aren't doing the best. Too them to the fair, so maybe had them in more sunlight than I would have here. But also I need to trim up the spent blossoms because now they are just making single blossoms. They are the female part of the plant and all the energy is going into making seeds for survival. If you are having not the double blooms that is what you need to do.
How to Grow Non-Stop Begonias By Fern Fischer;
Non-stop begonia plants bloom all summer.
Non-stop begonias grow from tubers, and are also called tuberous begonias. They bloom continuously all summer. Just before the first frost, trim the foliage and dig up the tubers for winter storage. Non-stop begonias are not cold hardy, and they require a dormant period.
Non-stop begonias are available in dozens of color combinations; the plant habit may be upright or trailing. Choose the species with the characteristics that suit your purpose.
Select non-stop begonia tubers that feel firm and solid. Small sprouting buds may even appear on some tubers. These tubers are ready to grow as soon as you get them into soil.
Start the tubers indoors in flats for the earliest flowers. Start them about 8 weeks before the last expected frost for your area. Plant the tubers 1/2 inch deep in shallow containers. When two leaves appear from each tuber, move the tubers to individual 4- to 6-inch pots.
Pinch off the first early flower buds so the energy goes into growing stronger plants.
Prepare a garden bed by tilling the soil until it is finely textured. Add compost to improve the soil. Begonias need a location with partial shade and well drained soil. Dappled sunlight is ideal. Tubers will rot if they become water-logged.
To plant non-stop begonias in a container, fill a clean planting container with humus rich potting soil. Transplant the begonia plants to the garden bed or to outdoor planting containers after the danger of frost. Set the plants at the same depth they were growing in the small pots. Water and feed the begonias after transplanting. Allow the soil to become nearly dry to the touch between watering again, but don’t let it get completely dry. Check containers daily. Containers dry out quickly and need more frequent watering than garden beds. Feed non-stop begonias with diluted fertilizer every two weeks. Remove spent blooms to encourage more flowers and keep the plants tidy.
Pinch off the female flowers to keep the plant from wasting energy developing seeds. Non-stop begonias bloom in groups of three flowers. The large flower in the center is the male, and the smaller flowers on each side are the females. Very important to do.......
Examine your begonia tubers. One side is indented, or bowl-shaped. Plant this side up. The leaf and flower stems grow from the indented side, and so do most of the roots. You may notice small buds sprouting when you plant the tubers; they are leaf buds. Be careful not to disturb them.
For a fuller effect in a large container, use two or three plants instead of just one.
taken from https://www.gardenguides.com/112886-grow-non-stop-begonias.html
till next time this is Becky Litterer, Becky's Greenhouse Dougherty Iowa firstname.lastname@example.org