When the weather cools in the Valley, and blooming flowers for the shade garden are sought, primroses are often proposed.
In truth, primroses are not really meant for the Valley and, although they are perennials, seldom live in our gardens more than two or – at the most – three years. They are frequently treated as seasonal annuals, planted at this time of year and removed in the spring.
The reason for their brief life in our gardens has to do with the heat of our summers, the low humidity we experience throughout the year and the alkalinity and imperfect drainage of our soil. Primroses are better suited to the cooler, moister climate of the Pacific Northwest – where the soil is acidic and fast draining – than to our own back yards.
Nevertheless, it is possible to keep primroses for two or three years if they are correctly situated and planted in properly prepared soil. They do best in high shade, which means they should be planted in the shade of mature trees or in open north-facing exposures, where plenty of filtered or ambient, yet indirect light is available.
It is imperative that snail bait be scattered around plantings of primroses. Snails find primroses irresistible. Where snail bait is not used, you may plant primroses today only to wake up tomorrow morning to find them vanished, as if some garden prowler had stolen them during the night.
There are three main types of primrose (Primula species) available in nurseries now: obconica, malacoides and polyantha. My favorite is Primula obconica. It has large leaves, which are virtually round in shape and, under ideal circumstances, can reach 4 or 5 inches in diameter, while the plant itself will not grow more than a foot tall. Even without flowers, which appear mostly during fall and winter, Primula obconica can be appreciated for its unusual foliage.
Primula malacoides is a species whose leaves are also roundish, only much smaller in size than obconica’s. Malacoides is a larger plant than obconica, reaching a height of 18 inches. Both types of primroses have flowers in the pastel range, including salmon, rose and lavender.
The third member of the primrose triumvirate is Primula polyantha, the English primrose. Its flowers are bright and vivid, especially when glowing from a shady spot, and open up in all the colors of the rainbow. There are also some recently introduced blended color cultivars.
These three primroses are partial to an acid soil and will show chlorotic or yellow leaves where soil is too alkaline. In order to acidify the soil prior to planting, make sure you work in lots of compost with a spading fork.
If you add peat moss, which is also acidifying, make sure you also add some washed sand (one part sand for every two of peat). The reason for this is that peat moss is water-retentive and, unless sand is also added, will interfere with the good soil drainage that primroses require.
Cyclamen is a member of the primrose family with a much different look from that of the above plants. Cyclamen has silky, recurved petals in red, pink, mauve, or white, with distinctive v-shaped markings on its heart-shaped leaves. Usually grown and purchased as an indoor plant, cyclamen can also be planted outdoors, in climates such as ours, where winters are mild. Cyclamen plants grow from tubers that should just barely be covered during planting. These tubers survive from one year to the next as long as they are not over-watered during dormancy, which, for them, occurs during most of the spring and summer.
Cyclamen are very long flowering in the garden and will bloom without interruption from now until spring. However, after flowering ends and all leaves have finally disappeared, watering should not be resumed until next fall.