Brazen Flowered Tuberous Begonias

Spectacular, colorful, almost too perfect flowers...

Tuberous begonias flower from late spring, when the daylight reaches 13 hours long, until well into autumn when the foliage dies back. These tuberous-rooted perennials have been extensively hybridized and refined to the point where the larger-flowered forms are nothing short of spectacular. For gardeners with greenhouses or a very mild winter climate, there are types that flower well into winter, and right through the cooler months.

Description and classification and groups

Begonias are among those conveniently labeled plants where the proper name is also the common name. The genus is found in the tropics and subtropics, particularly in the Americas. It is made up of around 900 species with 130-odd in cultivation, from which many cultivars and hybrids have been developed. These garden forms have been divided into 8 main categories. They are:

1. Cane-like, which have narrow, upright stems with conspicuous leaf nodes and evergreen foliage.

2. Shrub-like, which are bushy plants with branching stems.

3. Thick-stemmed, which resemble the cane-like, but with much heavier stems that sometimes form a trunk.

4. Semperflorens, which are the fibrous rooted types usually used as summer-flowering bedding annuals.

5. Rhizomatous, which may be evergreen or deciduous and which are often grown as much for their foliage as for their flowers.

6. Rex-cultorum, which are the fancy-leaved Rex begonias that are usually grown as house plants.

7. Tuberous, which have thickened tuberous roots and which usually die back over winter or, in the case of the winter-flowering types, may be dried off at some other time.

8. Trailing Scandent, which are pendulous, ever-blooming plants often with long internodes. Note:  Do not confuse these with the trailing tuberous begonias!

Although quite a few begonia species have tuberous roots, when speaking of tuberous begonias, we are referring to the fancy-flowered group of garden-raised plants known as Begonia × tuberhybrida. Developed mainly from South American species, they first appeared in Europe in 1867. This is just a three scant years after the introduction of the most influential of the early parent species, Begonia pearcei. Since that time thousands of hybrids have been raised. Today we have tuberous begonias in a wide range of sizes and styles of flower and growth habit.

There are small- medium- and large-flowered hybrids. You will find single, semi-double or fully rose- or camellia-like double flowers. Tuberous begonias may be small and mound-forming, trailing or upright to nearly 3 feet tall. And while the flowers are spectacular, the foliage is worht noticing, too. While unlike the Rex begonias,for example, tuberous begonias are never grown for their foliage alone, their velvety, deep green leaves are the perfect foil to the flowers. The contrasts are delightful.

Cultivation

So, tuberous begonias are beautiful, but how do you get the best out of them?

Begonias have a preference for cool, moist conditions. They prefer a climate that doesn't suffer from extremes of summer heat or winter cold. They need bright light to flower well, but should be out of direct sunlight, especially during the heat of the day. They need to be sheltered from strong winds which can cause the flowers to brown at the edges and tear or bend the soft foliage. Tuberous begonias flower love humus-rich soil, plenty of moisture and regular feeding.

With these requirements, many gardeners choose to cultivate tuberous begonias indoors, as conservatory, shadehouse or cool greenhouse plants. However, if you have a bright northerly facing position in your garden or a shaded spot facing south, then begonias will thrive outdoors too, particularly in areas that don't often experience drought conditions in the summer.

Strong sun and wind, especially hot dry winds, are the main enemies; light soil that dries out quickly doesn't help either. But in a lightly shaded, sheltered position with soil that has been thoroughly prepared with plenty of well-rotted compost, tuberous begonias will flower from early summer to the first frosts. Stake the tall growers to bamboo canes or wire frames, remove any spent flowers, keep the soil moist and add a little liquid fertiliser every week.

B. 'Sugar Candy', Photo: Ian McNeur

If you find that the super-fancy, large-flowered forms are simply not tough enough for your garden, don't dispair. Try some of the smaller-flowered hybrids. The little Multiflora types, commonly known as Flamboyant Begonias, are very resilient. Grown as massed bedding or in clusters, they're most commonly seen with bright red flowers, which often almost hide the foliage. Orange and a somewhat weaker yellow-flowered form are also found.

Nonstop begonias are crosses between the Multifloras and the larger flowered types. As you'd expect they're of intermediate height and vigour. They flower continuously, even in winter if kept indoors, and are available in a wide range of colours. Nonstops are F1 hybrids so there is no point in saving the seed. (An F1 hybrid will rarely produce plants of comparable quality as the parent.) Any seedpods should be removed to keep the plants flowering. Reiger begonias, developed from Begonia × hiemalis, are similar.

If open beds don't seem to work, consider growing your begonias in pots so that you can find just the right place for them. The upright types, flower and grow well, but are rather brittle, necessitating staking. The trailing types, often Begonia boliviensis hybrids, have more flexible, pendulous stems and when grown in hanging baskets they are easy-care plants that make a great show. Trailing begonias usually do best in sphagnum-lined wire baskets rather than solid pots, their roots appreciating the cool moist sphagnum.

Disbudding and deadheading

Begonias have separate male and female flowers. Usually one large female flower is subtended by two smaller male flowers. Removing the male flowers before they mature will allow the showier female flowers to reach their full size. This will also prevent the development of seedpods that could lessen the plant's vigour. Old flowers should be removed once past their prime. They snap off easily and doing this not only encourages new blooms to form, it also helps prevent fungal diseases that could develop among the decaying petals.

Pests and diseases

Begonias are neither particularly susceptible to nor resistant to pests. Slugs and snail relish the young shoots and the mature foliage. Various caterpillars may chew the foliage. Rasping and sap-sucking creatures such as thrips, aphids and mealy bugs may be present, but with a little attention and routine care, pests can usually be stopped before they get out of control.

A greater problem are fungal diseases, especially soft rots, mildew and botrytis. Damaged stems can quickly become soft, watery and rotten leading to the eventual collapse of the plant. Almost inevitably the foliage will develop mildew in late autumn - it's just part of the winter die-back process - but mildew can also occur during the growing season. Good ventilation goes a long way towards controlling the severity of fungal diseases. Keeping the foliage and stems reasonably dry, though spraying with a fungicide maybe necessary, too.

Winter care

As flower production lessens from mid-autumn, cut back on watering and feeding and allow your begonias to dry out. While the foliage should dry, brown and then fall away without too many problems, keep an eye open for any fungal diseases that could spread to the tubers.

Once the foliage has dried, the tubers may be lifted or removed from their pots for winter storage. This isn't always necessary in mild winter areas, but where hard frosts or prolonged wet conditions are likely, it's a good idea. Store the tubers in barely moist sawdust or any other fairly dry, inert medium, such as damp, shredded newspaper. Replant them (concave side up) in spring as the new shoots appear. Cover the tubers with a few centimetres of soil, as they sprout roots from the tops too.

The exceptions to the process are the winter-flowering Begonia × hiemalis hybrids, a result from crossing Begonia × tuberhybrida with Begonia socotrana, a species from an Indian Ocean island off the caost of Yemen. Widely sold as Reiger or "blush" begonias, these plants start to flower from late summer and will remain in leaf and flower until spring. Obviously these plants, which are completely intolerant of frost, need a very mild, benign winter to grow outdoors. However, they are very adaptable to indoor cultivation. They make a great choice for winter-flowering house plants that can spend the summer outdoors in the garden.

Propagation

There are several ways to propagate tuberous begonias, the method used varying with they type of plant.

Seed

Sow bought seed to produce F1 hybrids such as the Nonstops or to get a new crop of vigorous young plants.

Begonia seed is very fine, almost dust-like. It's so fine, that it doesn't usually come in seed packets, where it would be lost in the folds, but in glass phials that have to be snapped open before sowing. Pelleted seeds are much easier to handle, though they are not always readily available.

The seed needs warmth and light to germinate. It should be sown in spring, uncovered, in heated trays. Keep the seed just moist until it germinates. The young seedlings grow quickly and are soon large enough to pot. When small they are sensitive to draughts and temperature fluctuations. They should be kept under cover until spring is well settled into early summer.

Prepare your garden beds with high-humus compost and organic fertilizer. Because the foliage will be tender, plant out when the weather is not too hot and sunny.

Division

Mature plants have large tubers that divide readily. Division is a good way to quickly produce established, sturdy plants. Divide the tubers in spring when replanting. They slice easily with a sharp knife, but because finding the growing 'eyes' can be difficult, keep your divisions on the large side. To prevent fungal diseases, dust the cut surfaces with sulphur powder and allow them to dry before planting.

Cuttings

Most tuberous begonias will grow from cuttings and this is an especially good method of building up large stocks of the small-flowered Multiflora types for massed bedding. The fresh spring and early summer shoots make the best cuttings and will strike very quickly under mild humid conditions. You can continue to take cuttings well into summer. Note:   Unless the new plants can develop reasonably sized tubers before winter, they will probably not survive into the following spring.

Like many of the house plant begonias, Begonia × hiemalis is often raised from leaf cuttings. This involves removing a mature leaf, slicing across its veins and pinning the leaf down on moist soil. A warm humid environment, such as an enclosed propagation tray, is essential. Also, you should start in spring so that the young plants are well-established before winter.

Begonia displays

About the author:  Geoff Bryant writes garden books and is a horticultural photographer based in Christchurch, New Zealand. His stock photo library is called Country, Farm and Garden at (www.cfgphoto.com).

News about Tuberous Begonias

Take steps to save cherished plants from first frost Anchorage Daily News (subscription), AK - Sep 4, 2008 All your tuberous begonias, dahlias and gladioli can take light frosts. However, tuberous begonias do better with a much more gradual, indoor-induced ...

Aptos Times

Capitola Soquel Times September 1st Issue Aptos Times, CA - Sep 2, 2008 Native to South America and southern Africa, tuberous begonias are popular for their beautiful flowers, which come in a variety of colors and forms. ...

Capitola Begonia Festival blooms Labor Day weekend Register Pajaronian, CA - Aug 20, 2008 The begonia festival, rooted in the moist, coastal climate of Santa Cruz County that has provided hospitable growing grounds for the tuberous begonia since ...

Lushness and balance Chicago Tribune, United States - Aug 10, 2008 ... and annuals such as sunflowers, morning glories and tuberous begonias are carefully selected so there is something blooming all season long. ...

Exotic climbing liles set the stage for fall bloom The Daily Advertiser, LA - Sep 6, 2008 The easy-to-grow tuberous vine reaches 3 to 6 feet in height. It likes full sun, plenty of water and a support to climb on. Although it dies back after the ...

Perking up, settling down Milwaukee Journal Sentinel, WI - Aug 29, 2008 After frost has browned the foliage of non-hardy summer flowering plants such as canna, dahlia, gladiolus, caladium and tuberous begonia, they should be dug ...

Thank God for hard landscaping this summer Burnley Express,  UK - Aug 22, 2008 The winners, without doubt, once again are the begonias. Both the tuberous large flowered types and the small flowered bedding (semperflorens) have been ...

Bach festival a perfect excuse to explore Carmel, Calif. Hilton Head Island Packet, SC - Aug 16, 2008 Flowering plants catch our eye from every angle, and we particularly note the intense, saturated hues of the lobelia, tuberous begonia, impatiens and ...

SOS appeal secures future for flower show John O'Groat Journal, UK - Aug 20, 2008 Results – Pot plants – One begonia double tuberous: 1, 2, 3, Margaret Clyne. One begonia multiflora: 1, C. Lyall; 2, Carol Martin; 3, Christine Lyall. ...