Primula Japonica

by Dot Plyler

Primula japonica may be the most satisfying of the genus for those who live in places like the Delaware Valley, Pennsylvania, in zone 6B. In areas where summers tend to be oppressively hot and humid and winters may lack snowcover, this obliging candelabra primrose can flourish. Demanding only adequate moisture and several hours daily of sunshine, P. japonica will happily bloom and set seed year after year. Streamside, bog or similar environments are ideal, but some care should be taken not to drown the plant. Fertilizer, although not required, will make larger plants. Be cautious not to use too much nitrogen risking and encouraging huge, cabbage-like foliage at the expense of flowering.

Flowers, which appear in May or June on three foot tall plants, range from a strong red, through pink and violet shades, to white. The variety ‘Millers’ Crimson’ has been extremely satisfying for me and has produced seedlings with the same flower shade as the parent plant. In her book Primroses in Spring Doretta Klaber tells us that her plants “live for several years.” Mine seem to go on and on, but perhaps since they seed in so freely I am seeing new plants and thinking they are the old ones.

Propagation from seed is easy. Seeds planted in flats stored in a cold frame over winter should produce abundant seedlings the following spring. My experience has been that the candelabra group seeds germinate best if given a cold period. In Norman Deno’s book Seed Germination, Theory and Practice, he describes success using varying temperatures (70 degrees to 40 degrees) for different time periods. He has experimented with fresh seed and some up to 2 years old. Norman also compares results from seeds stored dry and stored with cold moisture.

The British specialist John Richards in his book Primula gives us details on the oriental origin of this species, including some observations on crossing. He observes that P japonica is “not as promiscuous as some species, being self-fertilizing, and the triploid hybrids are sterile, so no backcrossing occurs.” No doubt this the reason my stand of ‘Millers’ Crimson’ retains its clear color.

Although I checked various references, I did not find any mention of common or serious problems affecting these plants: no insect pests, no fungal problems. No pathogens serious enough to be considered troublesome seem to occur. And I have seen none on my own plants. Even the deer and rabbits that regard most green things as delicious seem to forgo the P. japonicas. Of course that may change next season, but so far my plants have been immune to attack.

For the gardener with the question of what to plant in the wet spot, and for the gardener who wishes to use plants requiring minimal care, Primula japonica offers an ideal solution.

[The following reprinted from the American Primrose Society Pictorial Dictionary of the Cultivated Species of the Genus Primula, 1948]

Japonica: Endemic but not common to the two northern-most islands of Japan. P. japonica was one of the four species; the others being imperialis, prolifera. and poissonii, which Sir Joseph Hooker, in 1892, termed the “Imperial Primroses.” It has been proven at the Quarterly garden that japonica is perfectly hardy under adverse conditions. It has been grown on a hillside with little water and in heavy soil and has even nurtured baby plants to maturity without the prescribed care. The plants are not as large or as lush as plants grown by the waterside, but they are very beautiful in droves down the hillside. They grow in the borders with average border care, in fact they seem to grow and thrive anywhere the seed is scattered. Of course this part of Oregon is known for the humidity. Except for the inside of the calyx lobes, which are thickly coated with white or cream colored meal, the plant is free of farina. The 12" leaves are typical, 5" broad through the middle. The margin is sharply irregularly dentate: lighter green and thinner in texture than those of other candelabra. The scape is stout, erect, to 30" tall, bearing as many as 6 superposed whorls, the topmost umbel crowded. The original plant, before garden culture brought changes, bore purplish-red flowers. It is said that this species planted in a mass is a weed killer and this can easily be imagined as the huge tropical like leaves cover an area as densely as some of the soil hugging dandelion. We cannot get such a stand here as it is much too attractive to visitors. It is a fine gift for the neophyte as it is so easy to grow. Japonica is a deciduous perennial Candelabra and one of the first to appear in the spring. Its color is very recessive and tends to streak the coronas of the lighter japonica hybrids in the vicinity.

Photo Credit: Sally Arant