Primula

This is a large group of plants commonly known as the Primrose. They are mostly hardy perennial herbs and are natives of Europe and temperate Asia, Java and North America. Only one kind, P. magellanica, is found south of the Equator, in southern South America. Some Primroses, such as P. vulgaris, the English Primrose, bear their flowers singly on stems that rise straight from the base of the plant. Others, such as P. denticulata, P. obconica and P. elatior, produce their clusters of flowers in a head or umbel at the top of the flower stem. In another group, the flowers grow in an array of whorls spaced along the upper portions of the flower stems. Some Primroses can be grown in the rock garden, waterside or bog garden, some in the wild or woodland garden and others are suitable for growing in flower beds, greenhouses and gardens. The summers are too hot over most of the U.S. for growing many of the Primroses, but in the Pacific Northwest and other favorable areas many can be cultivated successfully. Only a few of the most tolerable plants can be grown in climates that are hot and dry. Hardy Primroses may be divided into two main categories: the bog or woodland kinds and the cliff and rock dwellers. There are also many Primroses that could be called meadow plants, because they grow best in the garden in beds of loam. Primroses that are grown in a greenhouse make gorgeous potted plants that bloom in late autumn, winter and early spring. The Chinese Primroses, which are varieties of P. sinensis, are favorites. There are two main types of Chinese Primroses, the large-flowered, which produce clusters of large flowers and the small-flowered or star (stellata) varieties, which grow tall and bear sprays of beautiful blossoms for many weeks in the winter and early spring. The small-flowered varieties are easier to grow than the Primroses with the larger flowers.

POTTING - Hardy Primulas: The bog kinds of Primulas grow best in wet places such as the bog garden, streamside or pond. They can, however, be grown successfully if they are watered generously in dry weather and if they're given a soil so rich in humus or vegetable matter it acts like a sponge and soaks in and retains moisture easily. Large quantities of leaf mold, cow manure, peat moss, or sphagnum moss should be mixed into the soil. An area that is shaded from strong sunshine should be chosen to plant these Primulas. The rock and cliff dwelling Primulas grow the best in rock gardens in loamy soil that has good drainage and never becomes too dry. Leaf mold, sand and a bit of limestone or rubble added would be beneficial.

Greenhouse Primulas: Successful cultivation of these plants depends on the atmosphere. They need a cool, moist climate. Even in the winter they don't need a lot of warmth. A 50-degree temperature is just fine and if it happens to fall to 45 degrees on cold nights, it won't be a problem. For their final potting, the compost should consist of two parts of fibrous loam and one part of leaf mold or peat moss. A liberal supply of sand, some bone meal, dried cow manure and some other fertilizer should be added. Primulas flourish in leaf mold. When potting these plants, make sure to slightly bury the ends of the stalks of the lowest leaves. If they're set too high, they'll tip over and need supporting by sticks. Placing them too high in their pots is one of the most common mistakes in the care of Primulas. During the summer months they need excellent ventilation. The more fresh air that they have the better off they will be. They also need shade from direct sunlight. Flower stems that start to grow should be picked off to encourage the plants to form good growth. Near the end of September or earlier, if there is danger of frost, they should be moved to a greenhouse that has a night temperature of 45-50 degrees. There the plants from the earliest sowing will begin to bloom towards the end of November.

Propagation

Hardy Primulas: Seeds should be sown as soon as they've been harvested. If sown immediately, they'll usually sprout quite well. If they're kept for only a few weeks before sowing they will take much longer to germinate; they will come up irregularly over a long period. The seeds should be planted in pots or pans filled with sifted loam, leaf mold or peat moss and sand. After potting, water them well and place them in a shady, north-facing cold frame or other shaded spot. Keep them covered with a sheet of glass and a piece of paper. As soon as they are big enough to handle, pluck them out and grow in the usual way. If the seeds haven't germinated by autumn, the pans can be placed in a shady spot in the open, exposed to frost and snow all winter. This will help germination and they'll usually pop up after the pans are transferred to a frame in the spring. When dealing with the seeds of rare and valuable Primulas, hope for germination should not be abandoned before 18 month or 2 years. The English Primrose (P. vulgaris) and P. auricula and their varieties can also be increased by dividing them as soon as they've finished flowering or by offsets.
Greenhouse Primulas: Seeds that are sown from March to May will form plants that bloom in November or early December all the way through February or March. Seeds should be sown in pans that have crocks in the bottom for good drainage and are filled to within a quarter inch or so of the top with finely sifted compost consisting of equal quantities of loam and leaf mold with a bit of sand added. The seeds are tiny, so carefully sprinkle them evenly and thinly over the surface. Before the seeds are sown make sure to thoroughly moisten the soil with a fine spray. Barely sprinkle fine soil or sand over them for a covering. Cover the pans with a pane of glass and a piece of brown paper or other material. Place them in a greenhouse that has a temperature of 55-60 degrees and they should sprout in a few weeks. As soon as they peek out of the soil, the glass and paper must be taken off. They must be watered carefully or they may get the damping-off disease, which will spread quickly if not watched. Don't water them from above, dunk the pans almost to the rims in a pail of water and as soon as there is moisture on the surface of the soil enough water has been soaked up. It's important not to let the soil become dry. As soon as they are large enough to be handled easily, say 1� inches high, they need to be transplanted separately into pots, or 2 inches apart in pans filled with the compost previously described, though a bit coarser. It is better to transplant them to pots because it's easier to repot them. Be careful not to over water. Don't apply water until the soil is moderately dry, then fill the pots to the rims with water and don't water again until the soil becomes fairly dry. When they're established in their pots, they should have a night temperature of 50 degrees. When the risk of cold weather at night is over, the plants should be set in a cold frame facing north on a bed of ashes or sand and not more than 12 inches from the glass. Keep the ashes or sand moist, this helps maintain a cool, humid atmosphere. If they have been planted in pans, instead of pots, they need to be transplanted to 3- or 4-inch pots before they become too crowded. During the summer, when they're well rooted in those pots they should be moved into pots, 5 or 6 inches around and consequently, into their final pots with the soil mixture advised above in the potting section.


VARIETIES

• Hardy Primulas: Bog or Woodland Dwelling: (The English Primrose)
  P. vulgaris (P. acaulis) and its variety
  P. vulgaris rubra; Polyanthus Primrose;
  P. alpicola;
  P.beesiana;
  P. bullesiana;
  P. bulleyana
  P. cockburniana;
  P. cortusoides;
  P. denticulata;
  P. elatior;
  P. florindae;
  P. helodoxa;
  P. japonica;
• P. nutans (Dies after flowering, replant seeds yearly);
  P. pulverulenta;
  P. rosea;
  P. sieboldii;
  P. sikkimensis;
  P. veris (Cowslip);
  P. whytei.
• Cliff and rock dwellers:
  P. auricula and its forms are
  P. bauhinii,
  P. serratifolia,
  P. ciliata;
  P. viscosa;
  P. rubra;
  P. villosa;
  P. capitata;
  P. chionantha ;
  P. farinosa;
  P. frondosa;
  P. helvetica;
  P. juliae ;
  P. vialii (littonia);
  P. marginata and its hybrids
  P. marven,
  P linda pope, a nd P. rehniana;
  P. parryi;
  P. polyneura (veitchii);
  P. spectabilis;
  P. pubescens (This is a name for a large range of hybrids--the Garden Auriculas).
• Greenhouse Primulas:
  P. obconica (winter flowering);
  P. kewensis;
  P. floribunda;
  P. verticillata (winter and early spring flowering);
  P. malacoides (Fairy Primrose-fall to spring flowering).