These are popular summer-flowering plants which also have handsome foliage. The velvet-like blooms are available in shades of red, purple, rose and white.
Gloxinias are best raised from seed and if this is sown in a temperature of 16 to 18°C. (60 to 65°F.) in January or February, flowering plants will be available by mid-summer. The seed is fine and must be sown thinly in pots of seed compost. It is not necessary to cover it. Stand the seed pots in a propagating frame and the seedlings should appear in 14 to 21 days. Prick these out into boxes of John Innes No. 1 Potting Compost and place in a warm atmosphere with shade from the sun. Growth is rapid.
When high temperatures cannot be maintained in the early part of the year, plants can be raised from tubers in March and April. These are pressed into boxes of sand and peat, hollow side uppermost, and kept in a warm, shaded part of the greenhouse. A moist atmosphere should be maintained by spraying overhead with water. Before the plants grow too large move them into 5-in. pots of John Innes No. 2 Potting Compost, covering the tubers with 1/2 to 1 in. of compost.
Plants raised from seed and pricked out in boxes are first put in 3-l/2in. pots of John Innes No. 1 Potting Compost and moved subsequently to 5- or 6-in. final pots. Keep the developing tubers at or slightly belowlevel and do not make the compost too firm.
Shading and Ventilating
A summer temperature of 16°C. (60°F.) is ideal for plants raised from seed or tubers. Shade from sunshine, and maintain a moist atmosphere by damping down, but keep moisture off the leaves. As the plants come into flower lower the temperature by increasing the ventilation whenever possible.
Watering and Feeding
Little water will be needed for a few days after potting but then it must be given as the soil dries out. Feed with liquid or soluble fertiliser at 7- to 10-day intervals.
After flowering gradually give less water and ripen the tubers by standing the plants in a cold frame. Then, in autumn, return them to the greenhouse to dry off completely. Store tubers during the winter in a warm, dry place.
This method of propagation is not often adopted but it is the best way to increase a particularly good plant. Remove a mature leaf with the leafstalk. Preferably in early summer, and insert it in a bed of peat and sand in a warm propagating frame. Small tubers soon form and can be potted individually.
Alternatively, treat the leaves in the same way as those of Begonia rex. Cut the main veins on the underside of the leaves at intervals and place on a mixture of moist peat and sand in a warm propagating frame. Young plants will appear where the cuts were made.