Primula For All Climates

Nearly every garden, no matter how small, has a spot that receives sun for only an hour or so a day. It may be only a narrow border against the north side of the house or garage; it may be a space beneath a fruit tree; but it can be made a brilliant spot of color by planting some of the hardier primroses.

Many gardeners are unacquainted with the range of flower size and color that is available in some of the strains of primula. Brilliant reds, yellows and blues contrasted with pastels of pink, apricot and bronze; pure whites with yellow centers are set off by dark tones of royal purple, violet and brown fill the landscape color spectrum. There are few garden flowers that offer as wide a color range. Most of the flowers have an eye of a contrasting color, but in some of the newer strains there is only a trace of an eye or none.

A True Species?

primula red landscape

The polyanthus primrose is not a true species but is considered to be a hybrid originated in England perhaps three hundred years ago by crossing Primula vulgaris and the cowslip, P. veris. Several decades ago the polyanthus primrose was being developed almost entirely by English growers, but over the years progress has been made by primrose specialists in North America, particularly in sections of the West Coast where the climate is exceptionally favorable.

For the beginner, particularly if they live in the Midwest or South, the polyanthus is the best primula to choose to start a collection. It is as foolproof as any and the most rewarding in terms of color range, flower size and rate of growth. It is evergreen or nearly so, depending upon the latitude, and the many flowered clusters of bloom rise a foot above the ground.

There are three other primulas that are of almost equally rugged constitution. Although all members of the genus primula are often called primroses, the one to which the name was originally applied was P. vulgaris. Its foliage is like that of the polyanthus, but its single-stalked flowers easily distinguish it from the clustered inflorescence of its hybrid. Occasionally, however, some of the modern strains of P. vulgaris. tend to produce small low clusters toward the end of the blooming season. The color range is not quite as extensive as that of the polyanthus but the yellows, pinks and crimsons are good, and the shades of blue are particularly outstanding. Because of the habit of bloom, the plant seldom exceeds a height of 8 inches. Nurserymen in this country usually list this species as acaulis although vulgaris is the correct name.

Even more dwarf than the true primrose are P. Juliae and its hybrids, the Juliana primroses. Some of these are cushion-like in form and not over 2 inches high. Others are stalked but not more than half the height of the polyanthus. Named varieties are available and their color range continues to expand with further hybridization.

Strains of the bear’s ear cowslip, P. auricula, at times have been highly prized as a show flower in Europe, but only the comparatively rugged “garden auricula” is practicable for cultivation in most parts of this country. Its smooth succulent leaves are quite distinct from those of the groups previously mentioned. The fragrant purple, red, yellow or brown flowers are borne on stems intermediate in height between the polyanthus and the true primrose. It will get along with a little more sun and a little less water than most of the other primulas but in my experience is somewhat more prone to rot and attack by slugs which seem particularly partial to it. Therefore it requires a very well drained soil and some protection from slugs.

Generally Inexpensive

Most primula plants are comparatively inexpensive. Even large divisions are quite reasonably priced. However, the most inexpensive method is to raise your own plants from seed. If the growing season in your area is long, or if a greenhouse is available,. polyanthus, and garden auricula primroses will bloom the following year from seed sown in early spring.

Primula seed is known to be very slow germinating, sometimes taking several years, unless the seed is sown immediately after harvest. I usually sow seed that is at least six months old., since I prefer to start them indoors in late winter and transplant the seedlings to the garden in mid-September. I have germinated most acaulis, auricula and polyanthus seeds in less than two weeks by treating them as recommended by a Pacific Coast specialist.

The seeds are mixed with a few drops of water in a small vial and then placed in the freezer of the refrigerator for ten days. Twice during this period the seeds should be thawed out and refrozen. Then the seeds are freed of excess water by placing them on a towel or blotting paper. They are then sown thinly on the surface of soil in flats or pots. On two successive days they are sprinkled with hot. water (120°) and then with lukewarm water as necessary until they germinate. Recently I have been able to germinate 2-year-old seed in less than three weeks by this method. Seed may be sown on vermiculite or bagged seedling mix. Unless there are signs of mold, a plate of glass should be placed over the pot or flat until most of the seed has germinated. The seeds are not covered with soil but after they germinate, sterile sand should be sprinkled lightly among the seedlings. After several true leaves have developed, the seedlings may be shifted to roomier quarters or transplanted to permanent positions 4 to 6 inches apart.

In northern Indiana the season of bloom of the primulas mentioned is from mid-March until early June, depending upon the weather and the variety. The acaulis strains are the earliest. One of my sky-blue acaulis, growing in a sheltered position, is often in bloom with the snowdrops, and some of my largest polyanthas bloom with the iris.

Propagation and Winter Protection

The acaulis and polyanthas should be divided at least every other year by separating the clumps into individual crowns. It is often recommended that this be done immediately after blooming, but in regions where the summers are hot and dry this practice may result in considerable loss unless the divisions are kept well watered. Division in early fall is much safer if the plants can be protected during the winter by covering with evergreen branches. Division in early spring is perhaps the safest but it may postpone blooming. Winter protection is necessary primarily to prevent heaving from the ground and rapid temperature changes. Spruce, fir or hemlock branches are particularly good as a protective cover; a heavy covering of straw or leaves will favor rot. Where there is considerable snow, no mulch is necessary.

General Culture for Primulas

The general culture requirements of these primulas are simple. They enjoy a fairly rich soil but will tolerate the competition of roots of many deciduous trees and shrubs. My most successful plantings have been in the shade of fruit trees or shrubs. The soil should have a high humus content and be well drained. Since my garden soil drains very quickly and is sandy, I incorporate in it compost or well-soaked peat moss which adds humus and increases the soil’s water-holding capacity. A heavy soil could be lightened with peatmoss. Inorganic fertilizers should be avoided, but fish meal or manure are all excellent. During the spring and summer abundant moisture will produce the best growth, but the species mentioned, when planted in suitable soil in the shade require no more water than zinnias.

Disease and Insects

Diseases and insects are usually not serious problems. Red spider, which occasionally shows up during dry periods, can be easily controlled by any of the newer miticides. Crown rot will usually not occur if the soil is porous and the plants are not covered with heavy mulches. Slugs can be controlled with bait. After you have made a start with the most adaptable members of the primula group, you may want to experiment with the tall, later-flowering candelabra primroses and others which have more exacting requirements. But for most gardeners living in dry, warm regions, the rainbow colors of the polyanthus and the true primrose will continue to be the mainstay.

Contributed by J Jump

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