Primulas are grown from seed sown in well-drained pots using JI seed compost or a soilless sowing compost. The seeds are very fine and should be sown on the surface, after which tap the pots lightly on a solid surface, so that the seeds settle into the compost. Do not shade the seed pans but leave exposed to the light, but not direct sunlight, covering with a sheet of glass or a plastic bag.
As soon as the seedlings are large enough to handle they should be pricked out into boxes, if you are growing a fair number, or alternatively into 3-in (7.5-cm) pots, using JI No.2 or equivalent. At this stage it is most important to ensure that the seedlings are planted at the correct height, i.e. the crown of the plant should be level with the surface of the soil. If the crown is below the surface the plant will rot, and if above the surface it will not stand upright. The crown is the junction of the leaves with the stem. When the small pots are well-rooted, pot into 4-in (10-cm) or 4'/2-in (11-cm) pots, or if you have pricked out into boxes, transfer first of all to З'/г-in (8.5-cm) and later to 4'/2-in (11-cm) pots. For this final potting use JI No.2 or compost E6.
The sowing and potting culture already described applies to all six of the primulas with which we are concerned, but the growth requirements differ slightly, and at this stage it is necessary to differentiate. P. nialamides, P. kewensis and P. sinensis are best sown from early to late spring; P. obconica from late winter to mid-spring; and polyanthus and primroses late spring to early summer. All the primulas should be kept in a frame throughout the summer, and shaded from direct sunlight. At the beginning of autumn remove from the frame into the cool section of the greenhouse at first, until the weather becomes colder, then move P. obconica, P. kewensis and P. malacoides into the warmer section, where an average temperature of 45°F (7°C) is maintained. A drop to 4 0 - 4 2 ° F ( 4 - 5 ° C ) on very cold nights will not damage the plants. On the other hand P. sinensis requires a higher temperature, about 5 0 - 5 5 ° F ( 1 0 - 13°C). Polyanthus and primrose plants are kept in the cool section throughout the winter, as they are both hardy plants and will in fact stand frost.
Primulas are very useful plants for house decoration because not only are they attractive and colourful, but they flower from late winter to spring, a period during which flowering pot plants are not easy to find.
P. obconica will flower for months, but unfortunately has the disadvantage that it causes a skin rash to people who are allergic to the chemical secreted in the hairs on the underside of its leaves, and if you are one of these people always wear gloves when handling the plant.
A l l these primulas are treated as annuals and the greenhouse varieties are scrapped after flowering, but the polyanthus and primrose can be planted in the garden where they should bloom for years.
