By Michelle Le Strange, UCCE Master Gardener Advisor, Emeritus
f you are looking for a constant display of color throughout most of our growing season, consider begonias. The begonia family is huge, with more than 1,500 species with a wide range of plant size, foliage, flowers and growth forms. Taxonomists classify the family into categories based on how begonia roots grow. For example, there are fibrous, rhizomatous and tuberous begonias. The fibrous group is further divided into the “cane stemmed” (also called angel wing begonia) and bush type begonias (also called wax or bedding begonias).
The wax or bedding begonias (more properly termed Semperflorens cultorum) are the easiest begonias to grow. They are compact, low-growing (usually no taller than a foot) and bloom continuously from early spring through late fall. Flowers are usually an inch or so in diameter, in shades of red, pink or white, with waxy, rounded leaves that can be either green or bronze (there are some variegated leaf types, but we rarely see them offered for sale locally). Both leaf colors become more red as the amount of sunlight is increased. Some varieties have single blooms; others have semi double blooms, and all sport a yellow center. These begonias are grown mostly as annuals, but are really a perennial shrub type of begonia in areas that don’t freeze. I planted them at the entryway to our county office building and the majority of them survive the winter, but I do add a couple of flats each year.
Begonia breeders have developed a series of hybrid varieties. For example, there is the ambassador series (green leaf with red, rose, pink, white flowers) and the cocktail series: bronze-leafed varieties called gin (rose-pink flowers with bronze-red foliage), vodka (red flowers with bronze foliage) and whiskey (white blooms on bronze foliage). You can find these popular series at most local nurseries. They can be purchased in six packs, flats and gallon size in a single or a mixed assortment of flower color. When trying to highlight a pathway or entrance, I usually plant a single color for maximum impact. But I also like the casual look of mixed colors in landscape beds grouped with other foliage and flowering plants.
Although bedding begonias may appear fragile, they are widely used in commercial and utilitarian locations because of their relatively easy care and long-lasting flower and color impact. Several years ago, fibrous rooted begonias were mostly non-hybrid varieties, and these old varieties performed best in partial shade. Now many new hybrids have been introduced, displaying a diversity of flower color, foliage color and growth habit. These varieties can be grown in
full sun and actually perform better in sun than in full shade conditions. A thick layer of organic mulch (1-2 inches) helps keep the roots cool and cuts down on irrigation frequency. Water when the soil surface is dry. Good drainage is the key to begonia success. People have a tendency to overwater begonias in the full sun and the end result is plant death. If the soil gets really hot and is full of moisture, the roots will “cook” and rot away.
Today’s fibrous rooted begonias require little maintenance, making them perfect for home landscapes. You don’t need to deadhead these plants, but it is sometimes necessary to pinch back twiggy growth to promote bushiness. For the best effect, bedding begonias should be placed 8-12 inches apart in the garden.
A 6-inch spacing is too close unless one desires a continuous line of color. Begonias thrive on light, slightly acid, well-drained organic soil. To improve the soil structure and increase the drainage of heavy soils, add a substantial amount of organic matter such as peat moss, leaf mold or compost. Begonias are not heavy feeders, so fertilizer should be applied sparingly.
Begonias are not susceptible to many pest problems; however snails, slugs and whiteflies are common around here. Root rot caused by the pythium fungus and brought on by overwatering can also mean their demise and occasionally they suffer from bacterial leaf blight.
Few other annuals can beat the fibrous-rooted begonias for hardiness and continuous bloom throughout the summer season. The American Begonia Society website offers more information about their favorite plant: begonias.org.
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