Begonias by vegetative propagation.
There are several types of cutting from which begonias can be grown and the type of cutting does depend on the type of begonia to a large extent.
Great way to grow rhizomatous begonias including rexes. Not so good for cane begonias, less guaranteed results.
- Small leaves: Cut stem(petiole) about 2.5cm from leaf base. Insert stem in depression made in prepared growing mix at 45º angle. Gently firm mix and water in. Callous will form on the cut end and small plantlets after 8-12 weeks.
- Large leaves: On the underside of the leaf cut into several of the large veins. then lie the leaf on the top of prepared growing mix, checking that leaf is in contact with mix. You may need to use small weight to ensure this contact and leaf flatness. Small plantlets will form at the cut veins after a period of time.
- Large leaves: Using wedge cuttings of the large leaf, ensuring each wedge base ends with a leaf vein. Insert the cutting in the prepared growing mix at 45º angle. ensure cutting is firm and watered in. New plantlets and roots will form at the cut end of the vein.
- Creeping rhizomes: remove the growing tip of the rhizome with at lease one leaf and half bury it in growing mix, ensuring the root side is down. New roots will soon be followed by new leaves.
- Up-right rhizomes: take the cutting as above but insert it in the growing mix, in a similar way to what it was growing and stake it. New roots will be formed in a short space of time followed by new leaves.
Basic Tuberous Begonia Cultivation
The following is an abridged version of the talk given by Graeme Peake during the Begonia Festival and Show, Auckland, New Zealand, in February 2014.
• Pipping, small pink pips, new buds, appear on the top surface of the tuber.
• Plant piped tubers in a mix of half sand, half standard potting mix. Standard potting mix can be used in the bottom 2 cm of the pot.
• The diameter of the pot is no greater than 2 times the diameter of the tuber. The tuber is only just under the surface of the mix.
• Water lightly so the mix is just damp.
Final pot (November)
• When the first pot is full of roots it is time for the final pot.
• For a tuber 4cm diameter or greater chose a 3 litre pot; tubers 2 – 4 cm diameter choose a smaller 2 litre pot.
• Plant in standard potting mix, keeping the tuber at the same depth.
• The leaves of the plant will roughly point in the same direction that the flowers will face.
Watering (Nov, to Feb)
• Use rain water if you can.
• Water when the top of the mix is dry and pot feels light. If using clay pots, tap them lightly to check moisture content. You will hear a lighter, less dull sound.
• When the plant is small and roots do not occupy all the mix, be sure not to over water, perhaps every 5 to 7 days apart
• Mature plants water every 3rd day until water runs out of the pot.
Maintenance (all growing season)
• Remove the first flower buds.
• Remove female flowers (smaller flower with seed pod at the base)
• Stake plants and flowers.
• Good potting mix with slow release fertilizer will last the whole season. Extra feeds of liquid seaweed or similar can be used. Remember that too much nitrogen causes soft leaf growth.
• House plants under 30 to 50 % shade cloth. Ensure good air movement around plants, do not expose to wind or direct sun. (Tuberous begonias can be grown where they are in early morning/late afternoon sun.)
Pests and diseases (all season)
• Leaf roller caterpillars; like flower buds. Look for droppings (frass), spray with insecticides or use digital control.
• Powdery mildew; whitish grey powder on leaves; keep plants well spaced for good air movement. Select plants which are not prone to mildew. Some fungicide sprays will leave a residue on the leaves.
• Tarsonimid mites distort growing tips, cause russet on stems. Mites are too small to see. Keeps good hygiene cleaning pots, benches, etc each season? Isolate infested plants to prevent spread. Spray with preventative miticide.
• Tuber rot; happens any time, even in winter on dormant tubers. Cut out rot, dab wound with neat fungicide or dust with sulphur.
• Wilting plant; often too much water or stem/tuber rot.
Stop watering (April)
• Apply potash fertilizer 1 month before you stop watering. This helps mature and harden the tuber.
• Stop watering when nights get cooler and days shorter and the older leaves start to turn yellow.
• Remove all the flowers and the top 20 cm of the plant.
• Leaves will fall off and eventually .The stem will be rejected from the tuber, do not force this, allow it to come off naturally.
• When the potting mix is dry, lift the tuber, trying not to break the larger roots.
• Sit the tuber aside leaving the old mix still attached for more drying.
• Brush the old mix off carefully, not damaging non dried roots.
Storage (July to Oct)
• Dip tubers in 10% Demestos or 5% Janola solution or in straight Methylated spirits and dry. Dipping helps control/minimise storage rot.
• Store in a cool, dark place, they can be wrapped in paper or buried in an inert medium, eg. sand, sawdust.
• Inspect tubers for rot regularly. Light weight tubers or ones that sound hallow when flicked might be rotten inside.
• Dehydrated tubers, wrinkled skin, can be sprayed with a little water.
• At the point where the old stem joined the tuber a dry cap (scab) may form. This needs to be removed, a flick with a strong finger nail is best, do not damage the tuber.
Full Circle (Oct)
• Look for piping tubers and start over again…
• The best time to take cuttings is Nov and Dec to mid Jan. Late cuttings may not develop a tuber large enough before winter.
• Two types of cutting Base and Stem.
• Extra shoots may appear on the tuber, when they are 10 cm tall they can be harvested.
• Grasp this shoot at its base, where it joins the tuber. Gently rock the shoot back and forth, do not allow the stem of the shoot to bend, the cutting will break at the point where it joins the tuber.
• Dab tuber wound with meths or fungicide, not the cutting.
• Shoots that grow between the plant stem and the leaf stem are taken as cuttings.
• Sterilize a very sharp knife by rubbing with meths, allow drying.
• Cut between the new shoot and the stem also between the shoot and the leaf stem.
• Gently pull the cutting as you cut.
• The cuts will make a wedge shape on the bottom of the cutting.
• Trim excess leaves.
• Dab plant wound with meths or fungicide, not the cutting.
• Cuttings can be dipped in a rooting hormone.
• Put cutting into neat rain water 1 to 2 cm deep.
• Change water if it goes green.
• Pot in standard potting mix when roots appear.
• Another method is to plant cuttings in fine washed sand, and water in well.
• Roots should appear in 4 to 6 weeks.