Begonias
 
 
Looking for something to add colour and interest to your garden or room? Begonias are an excellent choice.
 
Bergonias are perennial plants known for their spectacular flowers and foliage.
 
 
 
The genus Begonia (which is both the botanical and common name) belongs to the Begoniaceae family. There are over 1200 species of Begonia, growing best in tropical or sub tropical climates. Begonia are also a popular choice in cooler climates as an indoor plant - a great way to brighten up a room.
 
 
Learn about more Tropical Plants here
 
 
 
 
 
Begonias hybridise easily and even species from separate continents have been bred to produce hybrid cultivars. Hence there is a huge range of cultivars available.
 
 
Begonias are an obvious choice to grow in a semi shaded or shaded area. They are well suited to a wide variety of climates, though excessive cold (eg. frost), direct sunlight or excessive dryness can kill or severely damage most types of begonias. Many will grow well as indoor plants; some are more commonly grown in a shade house or fernery; and others are grown as bedding plants.

 
 
 
 
 
 
 
 BIOLOGY OF BEGONIAS
 
  • Widespread, occurring naturally in the tropics and sub tropics of both hemispheres.
  • More common on continents than on the Pacific Islands.
  • Includes shrubs and low herbaceous plants (sometimes climbing).
  • Commonly succulent (soft) wooded, but sometimes more woody.
  • Most are perennial.
  • Roots can be either bulbous, rhizomes, tubers or fibrous rooted.
  • Leaves vary greatly in shape, size and colour; and are usually alternate along the stem.
  • Flowers usually white, pink, red, orange or yellow usually occurring in axillary cymes.
  • Male flowers have 2-4 sepals and 0-2 petals.
  • Female flowers have 2-5 equal tepals (NB: a tepal is like a petal or sepal, but not clearly one or the other).
  • Fruit is a capsule or very occasionally berry like.

 
CULTURAL NEEDS
 
Most begonias respond best to warm, moist conditions. The ideal temperature range is 15 to 26 Celsius though most will tolerate range is 15 to 26 degrees Celsius though most will tolerate temperatures as high as 40C and as low as 5C - some even lower.

 
All begonias prefer well drained soil rich in compost or organic matter and some like some degree of shade. Semperflorens and tree begonias however, tolerate more light than the others. In cooler climates, too much shade can reduce flowering, while in hot areas, too much sun will burn the foliage. All grow well in semi–shade or half–shade.

 
Fertilise with a liquid fertiliser at half the recommended strength, but apply twice as often. The soil should always be moist but never saturated or bone dry. Roots will easily rot if they become too wet. Foliage will shrivel and thin if the soil becomes too dry. Mulching is a good way to help maintain soil moisture.

 
Most begonias grow well in pots but be aware that it is more difficult to maintain an even soil moisture level with a container grown plant. Pot plants dry out quickly and over-watering is a temptation.


VARIETIES
 
Cultivated begonias are divided into nine major groups:
  • rhizomatous begonias
  • rex begonias
  • semperflorens begonias
  • cane–like begonias
  • shrub–like begonias
  • thick–stemmed begonias
  • trailing/scandent begonias
  • tuberous and semi–tuberous begonias
  • elatior begonias
 
 
Learn about other Perennials here
 
 
Rhizomatous Begonias
The outstanding feature of this group the rhizome - a swollen stem from which leaves and flowers arise directly. Most often the rhizome will be found to creep across the surface of the ground anchored downward roots, the leaves and flowers in an upward position. In some cases the rhizome has developed an upright habit and some of these begonias are ‘one–sided plants, the front being most attractive where the leaves and flowers grow out from the rhizome, but the back, where the roots would normally be, is quite bare.


Rex Begonias
Rex Begonias are also rhizomatous in habit, but are classified separately. They are distinctive because of their beautifully patterned and coloured leaves. The modern rex cultivars are happiest when used as indoor plants (in the right location). They are susceptible to mildew and for this reason many people regard them as hard to grow. Modern preventative fungicides have overcome this problem.
 
 
Semperflorens Begonias
Most gardeners will know this one - often referred to as the bedding begonia, or the wax plant, or perhaps ‘Thousand Wonders’. Some gardening books refer to them as fibrous–rooted begonias, but this description fits so many of the begonia groups that it is not really a proper description here. ‘Semps’, (as they are affectionately known) can be found in many council parks and gardens. They are widely used in gardens in Europe, and are at their best when they are mass planted.


Cane Stemmed or Tree Stemmed Begonias
These are taller growing plants with bamboo like stems, wing shaped leaves and drooping clusters of flowers. Foliage is not normally as dense as the semperflorens’ and the flowering not as prolonged; but the large leaves are often spectacular in both shape and colour. These are perhaps the most cold-hardy types.


Shrub-Like Begonias
The shrub–like begonias are also wonderful garden plants, and most should bloom throughout most of the year. As the name implies, these plants grow into a shrub–like habit, and can easily be pruned into shape. Shrub-like begonias also make good pot specimens and attractive cut flowers.
 
 
Trailing Scandent Begonias
Trailing begonias make excellent specimens for hanging baskets outdoors and as the stems of some species can grow to 2m or more and they are often used to train up pillars or posts. They flower profusely, with flowering periods varying according to species - some cultivars flowering throughout the year. They are easily contained with regular pruning. They need a sheltered position with filtered, but not direct, sun. Most trailing begonias have either pink or white flowers. Some have philodendron-like glossy leaves.
 
 
 
              

 
BEGONIA SPECIES

 

B. acetosa (syn. B. cantareira)

  • · fibrous rooted
  • · leaves to 30cm; coppery olive green with white hairs on top
  • · white flowers on 45cm long sprays

B. acontifolia

  • · fibrous rooted
  • · dark glossy green leaves with white markings on top and red underneath
  • · inconspicuous white or pinkish flowers. (Sometimes sold as B. metallica)

B. acutifolia (holly leaf begonia)

  • · fibrous rooted
  • · stems to 30cm or longer
  • · leaves around 7cm long
  • · glossy green leaves, with a few hairs
  • · large white flowers

B. albo-coccinea (elephant’s ear begonia)

  • · rhizomatous
  • · large glossy green leaves
  • · flowers white on the inside and red outside

B. albo-picta (Guinea wing begonia)

  • · fibrous rooted
  • · glossy green leaves with silvery spots
  • · small green to white flowers

B. X alleryi (a hybrid of B. gigantea and B. Metallica)

  • · fibrous rooted; growing to 1.8m tall; bronze green leaves with purple veins underneath.

B. alnifolia (alder leaf begonia)

  • · fibrous rooted
  • · climber or upright bush
  • · green foliage with sparse hairs and pink flowers

B. auriculata

  • · rhizomatous
  • · stems to 30cm long
  • · glossy green leaves with a silver green centre, and a cupped or wavy surface

B. bakeri

  • · fibrous rooted
  • · brownish stems to 60cm long
  • · leaves around 15cm long, bright green and reddish margins
  • · large pink flowers

B. boliviensis

  • · tuberous
  • · annual plant, erect habit at first but stems of up to 90cm long becoming arched as they grow
  • · succulent stems are green with sparse hairs
  • · leaves to around 13cm long
  • · reddish fuchsia-like flowers
  • · this is one of the parents of many commonly cultivated tuberous begonias

B. X cheimantha (Cheimantha hybrids or Christmas flowering begonias). A group of hybrids derived from B. Dregei being bred with B. socotrana).

  • · fibrous rooted herbaceous annuals
  • · branching stems
  • · green, toothed leaves
  • · large flowers over winter, usually pink

B. coccinea

  • · has short rhizomes, leaves 8-15cm long, and 5-10cm wide
  • · bright green hairy leaves
  • · white flowers

B. coralline

  • · sometimes confused with B. coccinea; but this has stems to 3m long
  • · flowers larger and more than B. coccinea
  • · glossy green leaves with white spots above and red-green underneath
  • · several named cultivars are grown, varying in both flower and foliage

B. cucullata

  • fibrous rooted; stoloniferous
  • succulent stems to 90cm long
  • glossy green leaves to 10cm
  • pink flowers in summer

B. dregei (grape leaf begonia or maple leaf begonia)

  • · tuberous or semi tuberous
  • · stems 30 to 90cm long, and reddish
  • · leaves 608cm long, light green with purple veins; greyish spots above and reddish underside
  • · white flowers in summer are scarce

B. gigantean

  • · semi tuberous plant with a woody rootstock
  • · stems 60-70cm long
  • · white or pale pink flowers

B. metallica (metal leaf begonia)

  • · fibrous (and hairy) roots
  • · leaves to 15cm long
  • · olive green leaves with metallic purple veins on top, paler veins underneath
  • · flowers 3 to 4cm across, pale blue to rose white

B. pearcei

  • · tuberous
  • · stems to 35cm long, succulent and branched
  • · leaves green above and dull red underneath
  • · erect bunches of yellow flowers around 3cm across

B. rex (painted leaf begonia)

  • · has a rhizome that creeps at or below the surface
  • · wrinkled leaf surface, usually a metallic colouration and a wavy margin
  • · foliage colouration is variable; these Begonias are grown for their colourful foliage effects
  • · there are many hybrids of B. rex

B. semperflorens (this is B. cucullata variety ‘Hookeri’)

B. semperflorens-cultorum (these are better known as B. semperflorens-cultorum hybrids)

  • · fibrous rooted bushy plants
  • · branching stems
  • · succulent leaves that are more symmetrical than B. cucullata var. Hookeri
  • · single or double flowers: shades of white, pink or red

B. socotrana

  • · semi-tuberous
  • · stems 15 to 30cm long, branched to some extent, slender and succulent covered with sparse hairs
  • · leaves 12 to 25cm across
  • · large numbers or normally rose pink flowers

B. X tuberhybrida (hybrid tuberous begonias)

This group has been derived through interbreeding several different species of South American tuberous begonias from the Andes including: B. boliviensis; B. Clarkei, B. Davisii; B. Pearcei; B. rosiflora; B. Veitchii etc.

B. Veitchii

  • · tuberous
  • · very short stems
  • · green leaves 3 to 6cm long, with main veins radiating from a bright red patch
  • · red flowers to 7cm across



PROPAGATING BEGONIA
 
 
Suitable types of cuttings - leaf cutting, tuber cutting, rhizome cutting or stem cutting generally strike easily.
 
 
Tree begonias are commonly grown by hard stem cuttings or semi-ripe tip cuttings, but shorter varieties are better grown from leaf or root cuttings. For tree Begonias cuttings can be taken most of the year (except winter). Early spring before new growth starts is usually the best time. Hardwood cuttings are ideally around 10cm long with the growth removed from all nodes except the top. For tip cuttings only the top pair of leaves is retained. The cuttings should be well spaced to give aeration around them to minimise the likelihood of fungal problems. A fungicide can be applied at regular intervals as well.
 
 
Tuberous type begonias can be readily propagated by tuber cuttings. These are taken in early spring from new growths cut off established tubers, and placed just below the surface in a peat/sand or similar mix, ideally with bottom heat supplied.
 
Rhizomatous type begonias can be readily propagated from sections of the rhizome.
 
 
 
Leaf Cuttings

Large leaves of some plants such as Begonias can produce new plantlets by cutting each of the main veins with a sharp knife or similar tool and then placing the leaf horizontally on the surface of the propagation media. New plantlets will form where the leaf’s main veins have been cut.


Leaf cuttings should be taken using a large, healthy leaf. The leaf can either have each of the main veins on the underside of the leaf cut with a sharp knife, or can be cut into sections (roughly triangular shaped down through the leaf with the base of the triangle at the base of the leaf)), with each section containing a main vein.


Cut areas can be dusted with a low strength IBA powder, make sure that you do not use too much as this can actually inhibit root formation. If the entire leaf is being used it should be laid down on the surface of a suitable propagation media, and lightly weighted down, or pegged down in some manner so that most of the underneath of the leaf is in contact with the media. Small amounts of the propagation media placed at selected spots on the surface of the leaf can be used. Be careful not to cover too much of the leaf as this will reduce photosynthesis. If leaf sections are being used then the bottom section of the cutting should be placed from one-third to a half of its depth into the propagation media. In both cases avoid over watering as the leaf can readily rot.


When new plantlets form at the base of the cut sections they can be readily lifted and transplanted into a suitable potting mix. The plantlets can form in as little as three to four weeks in good conditions.

 
Aftercare

High humidity is very important to reduce dehydration. (This can be achieved by placing plastic film over the cuttings, or using misting or fog).

Bottom heat and misting may not be necessary but can speed up the strike greatly.
 
 
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