Cultural Notes

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Tuberous

Environment

Sunlight. Choosing the proper environment for Tuberous Begonia is essential.  Begonias do best in partial shade or filtered sunlight. The right amount of light is often the key to success. Exposure to excessive sunlight results in burnt flowers and leaves. Too much shade results in foliage that is very lush with few flowers.

The more sunlight Tuberous Begonias receive without burning the larger and more abundant the flowers will be.

Places like cool greenhouses and shade-houses are ideal, preferably facing south or southeast. It has been found that “Polyflute” is ideal for the roof and for the sides 70% shadecloth.

Wind. Some protection from wind is essential. Begonias are quite succulent and can be damaged by strong winds. Light winds are however beneficial.

A collection of Tuberous Begonias growing in a shade house in Victoria

A collection of Tuberous Begonias growing in a shade house in Victoria

Starting Tubers

Tubers are started in September to October – it is important that a sprout or pink eye appears before it is planted (a bit like a dahlia). If your tubers are slow to move then move them from their cool winter storage to a warm light place. When the pink sprouts appear they are ready for planting. Always plant Concave side uppermost. Young tubers seem to give quicker results.

Fill a nursery flat or similar container with the planting media. A good mix consists of peat moss, perlite and sand, but there are many substitutes.

Space the tubers evenly in the flat or in the pot allowing 10 to15 cm between tubers for root development, that the tubers are covered completely is essential, as the roots develop from the top and sides of the tuber. REMEMBER – ALWAYS BURY THE TUBERS.

Water carefully, the tubers should be thoroughly watered so that the media is universally moist. DO NOT OVER WATER. Tubers will grow better on the dry side, and should never be left in wet soil for any length of time otherwise the tubers will rot.

Place the flats or pots in a warm place where it receives filtered sunlight. A temperature of 15 to 22oC is ideal. However, the cooler the tuber is grown the stronger will be the root system and the greater the amount of bloom later in the season. It should not be watered again until the surface of the soil begins to show dryness. As the plant develops it will require more water, but remember more tubers are lost through over-watering than any other cause.

Potting On

When the tops have reached about 7 to 10 cm high about early November, pot into a 10 to15 cm pots according to the size of plant. DO NOT OVER POT.

The potting mix should be a good open mix; a good commercial mix having the Australian Standard is usually quite satisfactory. It is beneficial to add a small amount of blood and bone and dolomite.

December. Repot plants into pots approximately 5 cm larger using the same mixture as before.

Allow 1 to 2 stems; excess stems can be used for cuttings. Disbud plants as they grow, and place a stake early in the growth. Begonias are one way facing plants, and the stake should always be placed at the back of the plant.

Fertilizing

Begonias do not require much fertiliser until they are in their final pots. Slow release fertilisers are good.  One fertiliser that is universally recommended, especially as the flowering season nears, either as a liquid or as tablets is “Phostrogen”.  It is easy and clean to use, is economical, and does not lower the pH of the media with continual use. Only use after the plant has been well watered.

Pests and Diseases

Tuberous Begonias are relatively free of injurious pests or diseases. Baiting can control snails, slugs and earwigs. Powdery mildew is the most serious problem you will encounter. This can be overcome by giving the plants adequate air circulation. A preventative program of spraying with a good systemic fungicide at intervals before flowering. White or paler colours seem to be the most effected.

If you find it present on the leaves (it appears like cigarette ash) swab it with a piece of cotton-wool dipped in methylated spirits. Fungicides recommended are “Rose Shield”, “Triforine” or “Baycor”.  Change your fungicides at regular intervals.

Handle all fungicides with great care.

Growing On

As the Begonias in the pot develop disbud the early flowers together with the two female flowers growing at the side of the male flower, unless of course you want to hybridize and collect seeds. You should remove the flower buds up to the middle of January, this way the later flowers are much larger. With the pendula varieties it is best to leave on all the flowers for a better display.

Resting Period

In late autumn  water less and remove all flowers and growing tips. This will commence the dying back process or dormancy. They are like all other tuberous or bulbous plants in that the strength of the tuber is dependent on the slow die back. Eventually the stem will die back completely and fall off, and this should give you a tuber that will bring pleasure for years to come. Store the tubers in a frost-free place during the cold winter months.

Cane-like

There are several hundred species and hybrids in cultivation today, and most originated in Brazil. Begonias of this group have erect or semi-erect stems with swollen nodes similar to bamboo. Most of the Cane-like do not branch readily, but send up new shoots from the base of the plant. There are many leaf shapes and colours varying from dark to light green, except for the Mallet types which have mahogany type foliage. Silver and white dots and splashes are prominent on many.

Leaf surfaces are either free of hairs or sparsely hairy. Most have a glossy or satiny surface, but some are dull. They vary in height from dwarf types and others from one to six feet or even higher, if one is able to grow them outdoors in the garden.

Most varieties are very floriferous, with long-lasting pendulous flowers or various colours ranging from white through pink, salmon, orange, red and rose. Many are ever blooming and others seasonal.

Cane-like begonias are divided into three main groups:

(a) Superba type.

(b) Mallet Type.

(c) All other.

The last group is divided according to height – low growing, intermediate, or tall growing.

Growing Conditions

Cane-like need plenty of light and at least 6 hours of sunlight a day, it may or not be filtered. In most area Cane-types should be protected from midday sun during the hottest part of the year. Cane-like begonias will tolerate a wide range of temperatures, but grow best probably between 14 – 23oC. They are not fussy as regards humidity.

Either earthenware or plastic pots may be used taking care not to over-water. As with most begonias, it is best to water early in the morning, and do not water again until the top of the pot feels dry to the touch.

Cane-like can take a heavier soil than other types. One part coarse sand, one part good soil, and one part compost is a good standard mix, with some blood and bone added. They benefit from a top dressing of animal manure occasionally or a liquid feed such as “Phostrogen”

Pruning is usually done in late winter or early spring. Young plants are not heavily pruned, just very lightly or the top pinched out. Older plants can be cut back hard. This encourages new growth from the base.

Tip cuttings 10-15 cm long can be used for propagation. Coarse sand is good or you’re proven mix. May also be increased from seed as with other begonias.

Superba Types –   ‘Irene Nuss’ and ‘Sophie Cecile’. The Superba types originated in 1926 by crossing a species Begonia aconitifolia with the hybrid  Begonia ‘Lucerna’.

Mallet Types – burgundy coloured leaved Canes. ‘Arthur and Tingley Mallet’, also ‘Margaritacea’. They need less hot direct sun than others do.

Tall Growing –  Begonia ‘Angularis’, ‘Lucerna’, and B. maculata.   Intermediate –  Begonia ‘Dorothy Barton’, and B.’Ortha C. Fox’.

Low growing –  Begonia albo picta,  B ‘Matild’, and B. ‘pinafore’.

Rhizomatous

This is the largest group of begonias in cultivation, there being well over 700 known species, and hundreds of cultivars both named and unnamed. As the name suggests these begonias have a rhizome which is essentially a thickened stem, and can roughly be divided into three main groups.

(1) Creeping rhizomes, (2) Erect rhizomes, (3) Rhizome at or below the surface.

The leaves of rhizome are very diverse in both size and shape, and are mostly derived from Mexico, Central and South America, and more recently Asia. These plants bloom once a year usually in late winter or early spring, producing a gorgeous flower cluster of very graceful habit. However whether in flower or not they usually have a spectacular display of foliage for which many are grown.

Cultivation.

Most rhizomatous begonias will flourish outdoors in our warm to hot climate provided we locate them with filtered sunlight without direct sunlight. Often large trees especially deciduous ones offer the right amount of light as do properly constructed shade-houses, and lath-houses etc.

Potting and Potting Media

In their natural habitat they grow in shallow leaf litter, and therefore these shallow rooted plants require shallow containers, and should never be over potted. They prefer a porous well-drained media.

Temperature

With few exceptions rhizomatous begonias enjoy temperatures in the range that humans are comfortable, that is in the range of 20 to 25 degrees C, they will of course adapt to lower or higher temperatures, but in cold conditions the plant will go into a dormant state.

Humidity

Rhizome begonias are not particularly demanding, and will tolerate lower humidity than a lot of other begonias. A good rule of thumb is the more exotic or distinctive the foliage the more humidity is required.

Watering

As with other begonia do not over water. The rhizome itself acts as a water storage basin for the plant.

Fertilizing

Only fertilise when the plant is growing away in the spring and early summer. Regular doses of low strength liquid fertilisers are preferred.  There are special requirements for the cultivation of certain rhizome and many can only be grown in terrariums.

Propagation

Rhizomatous begonias can be propagated by three methods, stem cuttings, leaf cuttings, and seed.

Stem Cuttings. Use sectional pieces or ends of rhizomes, plants will develop in a shorter period of time using this method.

Leaf Cuttings. This is the more popular means of propagating, and offers the grower either doing it by whole leaves or cutting the leaf into wedges thereby giving four or more plants to the leaf.

Seed. Use only the seed of species to get true to type plants.

Probably the best known rhizomatous is the beautiful  Begonia masoniana discovered in Malaya in 1955. The golden knobby leaves have a mahogany replica of the German Iron Cross in the centre, hence the name of the “Iron Cross” begonia.

Other well-known rhizomatous begonia are:

Begonia manicata an early species discovered in Mexico in 1839. Begonia ‘Cleopatra’ and  Begonia ‘Chantilly Lace’ are hybrids that make lovely baskets.

Begonia Rex

The original Rex Begonia was brought from Assam in India by mistake in a collection of orchids.

The leaf colourings are said to run the gamut of shades of precious metals – gold, silver, platinum, etc, and precious gems –  amethyst, ruby, garnet, topaz, emerald and opal. The leaf textures follows that of beautiful fabrics of silk, satin, velvet, brocade, crepe, tweed and soft woollens.

Begonia Rex. Cultorum are the most generous givers of themselves of all the begonias. In our climate seed may be planted late September through to February. As with all begonia seed, it is very fine so try not to breathe too heavily when working with it. Do not cover seed with mix after planting,  just press gently so seed  touches the seed-mix. A good mix is 50% peat moss, 50% perlite.

Leaves of these begonias will grow very easily from wedges placed half their length into propagating sand. They like humidity so indoors is only suitable if provision is made to create humidity. Best kept in bright light but not direct sun.

For good results grow them in a cold glass house with damp sand on bench tops. If the flowers are not needed for seed they are best removed as they take some of the vitality out of the leaves.

A fungicidal spray is needed to combat mould –  especially downy mildew – usually a good spray early November will be all that is needed.

A good open potting mix is necessary. By volume, use a good potting mix 50% and the other 50% perlite and peat moss.

Shrub-like

There are approximately 300 – 350 different shrub-like begonias species and cultivars grown at the present time. This makes them the second largest group to the rhizomatous group. Shrub-like begonias are chiefly grown for their beautiful and interesting foliage. They have leaves of all different sizes, shapes, surfaces, textures and colours. They also have different flowering times.

Like other groups of begonias they originated in Central and South America, but more recently a number of species have been discovered in Asia.

The group is divided roughly into the following classes:

Bare-leaves – further divided into medium and small leaved. Examples are  Begonia luxurians,  Begonia ‘Thurstonii’, and Begonia foliosa.

Hairy-leaved – a good example is the very old species Begonia scharffii.

Distinctive Foliage – some examples are  Begonia serratipetala, a New Guinea species, and  Begonia exotica hort, this one preferably grown under controlled conditions in a terrarium.

Miniature and Dwarf – Begonia acida also classified under distinctive foliage.

Begonias of this group are bushy and can be improved by constant pruning and pinching. The proper amount of light and/or sunlight is necessary for all begonias of this group, and like most other begonias strong direct midday sunlight is to be avoided, with further protection from all direct sunlight for the hairy-leaf types.

One of the advantages of growing shrub-like is that they can be brought indoors for their decorative leaves to be enjoyed in every season.

They enjoy a temperature between 11 – 22oC, however sudden changes in temperature are to be avoided as they will drop their leaves, and it might also effect their flowering season. They are not demanding as regards humidity around the 40% is sufficient, those with very distinctive foliage may need higher, and in some cases terrarium conditions.

Potting mix, watering and fertilising are similar to all other begonias, that is, an open mix, watering only when the media of the pot is dry, and fertilising only when the plant is in active growth.

Propagation

Stem cuttings are the most popular way to increase your stock. Leaf cuttings on some of the distinctive leaf types, but usually is not the suggested method. Seed of course, will come only true to type from species.

Trailing-Scandent

There are few of this type of begonia available however because of their habit they make good basket begonias.

Potting mix, watering and fertilising are similar to all other begonias, that is an open mix, watering only when the media of the pot is dry, and fertilising only when the plant is in active growth.

Growing Conditions

This type of plant grows well under 70 – 80% shadecloth with natural humidity.

Propagation

These plants propagate readily from tip cuttings or seed.

 

 

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