Cultivation
• The name primula comes from the Latin primus meaning first, and like most primulas, Primula sieboldii gets off to an early start. Growth, in southern England at least, begins in February when pale-green leaves begin to emerge from shallow-buried rhizomes, known as crowns. They can begin flowering as early as mid March and continue until May or even early June. The flowers have long enough stems for picking and may last two weeks in a vase.
• Many primulas grow in spring and then become semi-dormant during the drier summer months. This species, however, comes from a monsoon climate zone, where most rainfall is in the summer months – so it will not survive drought well.
• Plants in containers will benefit from feeding in spring and early summer, and should ideally be re-potted annually in mid autumn during their dormant phase. Foliage dies back in October.
• In common with all other primulas, Primula sieboldii need a cool root run in moist but well-drained soil and don’t like to be in direct sunlight, preferring light shade. In the wild they grow in woodlands and along the banks of rivers, so they particularly appreciate soil that has a high humus content.
• Like many other primulas – including the more familiar polyanthus and primroses – Primula sieboldii clumps grow outwards every year. The older central stems die back, which means they continually have to occupy new territory; if they fail to root at the outer edge they will die. In the wild, clumps will expand but then almost certainly decline as the soil conditions change – which is where their prolific seed production comes in to play.
• Over time the rhizomes will wander, so plants will ‘move’, sometimes away
from their labels. If circumstances are favourable large clumps can build up; if less so, growth will be patchy and plants will die out.
• If necessary, you can divide clumps in autumn simply by separating the living parts of the rhizome – any piece with a shoot and some roots should grow. Container-grown plants will need dividing regularly as there is a tendency for them to wander to the edge of the pot.
• Although propagation by seed can be extremely effective, there is no guarantee that the seed will come true. Ideally, it should be sown fresh, or as soon as possible in the autumn. Germination is usually very good and will occur in early spring, although it may be erratic.
• Vine weevil, which can affect many woodland plants with rhizomes, can be a problem. Insecticides and biological controls are available, although you can also trap the adult weevils under upturned citrus skins.