Begonias come in many different varieties. Some varieties are suitable for bedding plants and some are striking specimen plants. Whatever variety you may choose, begonias are considered an annual in our zone 3 climate. The most common varieties of begonias we have are the tuberous begonia, the wing begonia, and the wax begonia (Begonia Semperflorens). Begonias flowers are lovely, however the leaves of begonias are also showy because they have varying shades of green, some with spots, and the underside of the leaves are usually some rich shade of red, or burgundy. Most of us will buy begonias in the spring from local garden centers, and may feel that they are quite expensive. However begonia seeds are like powder and need to be started 4 to 6 months in advance to be planted outside. Tubers or cuttings also need special care if they are going to be marketable.
The characteristics of all begonias are the same. They need to be planted outside after there is no danger of frost and the night time temperature is above 50 degrees. They prefer nighttime temperatures above 65 degrees, and daytime temperatures of 75-85 degrees. If you are planting them in containers they need a potting mixture that will drain well. It should be mainly peat moss and perlite or vermiculite. If you are using sand, the fine play box type is too fine and will cake around the roots and cause them to rot off. They like sun, but shade from the hot afternoon sun. Water the base of the plant or from the bottom. Try to avoid getting water on the leaves. The soil mixture should dry out between waterings and feel dry to the touch before watering again.
Perhaps the oldest type of begonia is the winged begonia. Examples would be like the angel wing or dragon wing. The roots of this variety are fibrous, unlike the tuberous begonias, there is nothing below the ground except roots. There is no tuber or bulb to support the plant over the winter. Winged begonias are a member of the cane-type family, which get their name from the long stems that have bamboo-like joints. These are fast-growing specimen plants with large wing-shaped leaves with sharp edges. The leaves come in many different shades of green, with some leaves having spots on them, and the under leaf in shades of red or burgundy. They have loose clusters of red or pink bell-shaped flowers. They are excellent for growing in pots outdoors, solo or mixed with other shade loving plants. Growing to 16 inches tall and 18 inches wide, they like the heat, but thrive in partial to full shade or filtered sun. Prune to make the plant bushier and as the plant gets tall it may need the support of stakes. If winged begonias are grown in full sun, it will turn the edges of the glossy leaves and make them curl, but it will not harm the plant.
Another fibrous root begonia is the wax begonia. Wax begonias are small, growing only 5 to 12 inches tall. They are great to use for edging plants along a sidewalk or in the front of a flower garden, or the front of a container garden. They are called wax because of the shiny rounded leaves which are different shades of green to red. The flowers are small and can be single or double in white, pink, or red. These showy little plants will bloom continuously all summer until they freeze. The green-leaved variety prefer shade, and the red-leaved varieties are very tolerant of the sun. Many new heat-resistant hybrids are being developed to tolerate the sun.
Tuberous begonias are grown from tuber, come in a wide variety of colors, and do well potted in 8- to 10-inch containers. Over potting (pots which are very large) and over watering may kill a tuberous begonia. If the pot never seems to dry out the pot may be too large. Self-watering containers are good to use for begonias. But any pot will work as long as it has a drain hole and the potting mixture contains a large amount of peat moss, vermiculite or sand so it drains well. Tuberous begonias also need to be spaced properly to receive adequate light and air circulation. Tuberous begonias do well on the east side of the house where they get the morning sun, but not the hot sun of the afternoon. Powdery mildew may result if the soil cannot drain, their leaves are watered, or they are not spaced properly so that light and air can circulate around them.
The Rex begonia is usually grown as an indoor plant. It is grown for its beautiful leaves which have sharp toothed margins and are deeply incised and come in a variety of colors, textures, and shapes. Rex are a challenge to grow because they require low-light conditions, but also a constant humidity of 50 percent. To achieve the right humidity, the containers of Rex begonias need to be set on pebbles in a saucer or tray, with water filled to just below the base of the containers. To grow vigorously, Rex begonias require greenhouse-like conditions.
Kyle Schulz is a Wadena County Master Gardener from Sebeka, and the regular gardening columnist for the Wadena Pioneer Journal.