Few plants rival the stunning, season-long flowers of begonias — and even fewer bloom so abundantly in shade! Begonias are tender perennial plants that bloom nonstop with flowers in warm shades of red, pink, salmon, and yellow, as well as white and bi-color. They can be grown outdoors year-round in tropical and subtropical climates. In cooler regions they can be grown as annuals or enjoyed as houseplants during winter.
There are more than 1,500 distinct species of begonias, and plant breeders have created a seemingly infinite number of cultivated varieties and hybrids. Unlike most familiar garden plants, begonias bear separate male and female flowers, with both occurring on the same plant. Begonias can be broken into numerous categories, with the following the most common.
Wax begonias (Begonia semperflorens, aka fibrous begonias) are popular, low-growing bedding plants. Planted in groups, their vibrant flowers brighten shady to part-shade locations. Although the flowers are smaller than those of tuberous begonias, they make up for it with profuse blooms from spring to fall. Foliage is waxy and forms a compact, 8” to 12” high mound. Some types have green foliage, while others have bronze or purple-black leaves that provide a contrasting background for the flowers.
Tuberous begonias (Begonia x tuberhybrida) are the real showstoppers of the begonia clan, producing extravagant flowers that command attention. Some have double flowers that resemble roses or camellias; others have ruffled blooms that resemble carnations. Some have single blooms, while picotee varieties have petals edged in a contrasting color. Tuberous begonias are stunning in containers, windowboxes, and patio planters. One type of tuberous begonia, called the Bolivian begonia (Begonia boliviensis), is especially spectacular in hanging baskets where their draping, downward-facing blooms can be admired up close.
Rieger begonias (Begonia x hiemalis) are a cross between wax and tuberous begonias and offer the best of both. The plants are larger than wax begonias, so they make more of an impact when viewed from afar. Their blooms are held upright, making them a better choice for in-ground beds where the large, dangling blooms of tuberous begonias might get splattered with soil.
Rex begonias (Begonia rex-cultorum, aka rhizomatous begonias) are commonly grown as foliage houseplants. And what foliage they have! In addition to a range of green hues, leaf colors also include shades purple, red, silver, purple-black, and frosty white, often in intricate patterns. Leaf shapes vary too, including some with incredible overlapping swirls.
Growing Zones for Begonias
Most begonias are perennial in USDA Hardiness Zones 9-11. In colder zones they can be grown as annuals and either overwintered indoors or replaced with fresh plants each spring.
Choosing a Site to Grow Begonias
Give begonias a spot in dappled shade, part shade, or full shade. Full sun will result in crispy leaf margins and a shortened life span. They require fertile, well-drained soil to minimize problems with root rot. Wax begonias and Rieger begonias are ideal for adorning the front of a perennial shade garden, bordering walkways, or adding to mixed container plantings. Tuberous begonias do well especially well in containers, raised beds, and hanging baskets. If growing indoors, provide plants with bright, indirect light.
Planting Instructions for Begonias
Wait until all danger of frost has passed to plant these tender beauties outdoors. In the garden or in raised beds, amend soil with compost to provide nutrients and improve drainage. If growing in containers and hanging baskets, choose a freely draining potting mix and add some slow-release fertilizer prior to planting.
Tuberous begonias can be purchased as plants or grown from tubers. If you’re starting with tubers, get a jump on the growing season by planting them indoors 8 to 10 weeks before your average last frost date. Plant them in moist potting mix, covering the tubers with about an inch of soil. Move plants outdoors once all danger of frost has passed.
Mulch plants lightly after planting to conserve soil moisture, keeping the mulch a few inches from plant stems to minimize disease problems.
Fertilizer for Begonias
Begonias require plenty of nutrients to fuel their vigorous growth and season-long blooming. In addition to adding compost and/or a slow-release fertilizer at planting time, you’ll want to feed the plants monthly throughout the growing season.
Begonia Pests and Problems
Although relatively carefree, begonias do have a few potential pest and disease problems. Aphids, mealybugs, and whiteflies attack the foliage; these can be controlled with insecticidal soap. Powdery mildew, a fungal disease, causes powdery-gray patches on foliage; spacing plants generously to allow good air circulation helps prevent this and other diseases.
Ongoing Care for Begonias
Water plants as needed to keep the soil moist but not overly wet. Apply water to the soil, taking care to keep foliage dry to prevent diseases. Begonias need little or no deadheading, though you can occasionally remove spent blooms to keep plants looking tidy. Prune off any diseased or damaged foliage.
To save tubers for replanting: In fall, before the first frost, cut back foliage and dig up plants, leaving some soil around the tubers. Place the tubers in a warm, dry spot out of direct sun and allow them to dry for a week or two. Then shake off the soil and carefully prune off the stems and roots, leaving the tuber intact. Layer the tubers in peat moss or sand and store them in a cool, dark, dry place until spring.