Begonias; are named after Frenchman Michel Begon, and originated in Brazil.
Tuberous varieties are more suited to growing under cover in the UK as are Begonia bolivensis although these can be sat outdoors in a sunny sheltered spot for the summer months and should be returned indoors before the onset of early frosts.
Semperfloren varieties are well suited to flowerbeds, hanging baskets, containers, and as indoor house plants.
It is a half hardy annual often referred as a bedding begonia and sometimes as a wax or fibrous rooted begonia.
They grow to around 200mm (8”) high with a similar spread.
Fill tray with a 50-50 mix of compost and sharp sand, and thoroughly soak with water.
Mix the fine seed with silver sand and sprinkle on to the surface of the compost.
Place in a propagator set to give a temperature of 21°-24°C (70°-75°F) to germinate.
Germination should take about two weeks.
Prick out out when large enough to handle.
Tuberous begonias are tender bulbous plants that enjoy temperate conditions, so raise them in a heated propagator and grow on in a warm greenhouse.
They grow up to 500mm (18”) high and spread to around 300mm (12”) in diameter.
The flowers subject to variety can be up to 150mm (6”) in diameter and come in a variety of pastel shades.
Due to flower size the stems often need some form of support.
Similarly for this reason they are generally grown in a cool greenhouse or conservatory.
They can be placed out doors in a sunny sheltered spot for the summer months and should be returned indoors before the onset of early frosts.
Check over stored tuberous begonias if any show signs of rot, cut away affected tissue with a sharp knife, and dust wound with green sulphur powder.
Week 10 - 12:
Start up new / stored tubers;
Plant them together in seed trays filled with compost to encourage them into growth.
Space them out, then cover with a small amount of compost.
Once strong new shoots have developed, usually after a period of five to six weeks, tease the rooted tubers apart, leaving a mass of compost attached to keep all the thread-like new roots intact.
Tubers can then be planted separately in containers.
Sometimes it can be quite difficult to determine which way up to plant the tubers.
Begonia tubers look like flat balls covered with coarse fibres.
These fibres are actually old roots, and new ones will develop out of the entire surface area of the tuber.
Sometimes tubers have a concave side and a convex side, and you may see tiny white buds developing from the concave side.
This side needs to face upwards.
If the tuber has neither a concave side nor buds, stand it in a warm position until the buds develop. then you will know which is the top/bottom.
Gently press tubers into trays of gritty compost until tops remain just above the surface.
Keep containers in a minimum temperature of 16°C (60°F) and do not allow compost to dry out.
This task can be started sooner i.e. if these growing conditions can be maintained, and lighting is good.
Poor lighting can result in weak straggly plants hence the writer’s preference for the later date.
Take leaf bud cuttings of Rex varieties.
Trim the leaf stalk of a mature healthy leaf down to about 30-50mm (1½" - 2”) and insert one or more cuttings into containers filled with well-drained compost.
Alternatively, insert singly into Jiffy 7 peat pots before sealing in a plastic bag or propagator.
Water container grown begonias copiously and feed weekly to maintain strong growth.
Always water plants with care, to ensure you don't fill the concave upper surface and cause rot.
When watering from above, direct the flow around the edges of the pot, away from the tuber.
Alternatively, water plants from below.
To encourage flowers, feed with a high potash fertiliser, such as tomato feed, weekly through the growing season.
Support large-flowered tuberous varieties that have become top heavy or have weak flower stalks.
To assist stability with top heavy plants, pot up plants into larger pots if considered necessary.
Carefully remove the single female blooms from large-flowered tuberous varieties to allow maximum room for the central double-male flowers
Female flowers can be recognized by the winged seed capsules behind the flower.
To avoid outbreaks of fungal disorders, remove faded flowers and dead or damaged foliage regularly, apply systemic fungicide if mildew affects foliage.
Mrs E McLauchlan
Stop feeding tuberous begonias once flowering and growth begins to fall off, and decrease frequency of watering as foliage shows signs of fading.
Strong plants of the fibrous-rooted semperflorens type may be carefully lifted (if in flower beds) as bedding is cleared.
If these are potted up they should continue to give a display throughout autumn and into winter providing they are kept in a well lit position in a warm room or greenhouse.
Gradually reduce the water as foliage begins to yellow.
Cut back the tops of tuberous begonias as the stems begin to fall away and don't worry if the stems bleed at this stage.
Place the pots on their sides under staging to quicken the drying of compost.
Tubers can remain in their pots, but check for rot or damage, any suspect areas should be cut away with a sharp blade and dusted with sulphur powder.
Alternatively, remove tubers from their pots, clean away any remaining stems, dead roots and store them in a cool, frost free place.