Hardy Garden Primroses

Primadonna Primroses Of The Past

I was recently asked to write more about collectors’ primroses; here are excerpts from an article I wrote some twenty years ago that pretty much covers the topic. It’s fun to look back and remember my dear garden where so many plant marvels were adoringly grown. Today, these species and heritage varieties are still to be found, having outlasted many new varieties bred for quick color rather than garden longevity. I know it’s long, but it’s only part of a far longer piece. I know, really? Enjoy!

The Primrose Path

To anyone raised on English children’s books, the word spring conjures up an artless jumble of primroses, violets, and celandines, with perhaps a cheerful hedgepig peeping through the leaves. This mental association of primroses and England is quite common and has lead to an assumption that American gardeners living beyond the mild, maritime regions of Pacific Northwest can only raise primulas under glass. Though it is no coincidence that most primrose specialty nurseries and the bulk of the membership of the American Primrose Society are to be found there, hardy garden primulas are successfully being grown all across the country.

Indeed, though gardeners in frigid Alaska may indeed be growing fancy auriculas in greenhouse or windowsill, they may equally well be growing native species or alpine primulas in their open gardens, for more hardy primroses are lost to the mugs of August than the frosts of winter. In warmer parts, the subtropical fairy primrose, Primula malacoides, blooms from winter into spring, and P. obconica may proffer its pink and purple flowers all year round. While not every primrose is for every garden, it might prove hard to find a garden where no primula could thrive.

Wild And Tame Treasures

My own initial impression that primroses were delicate creatures was dispelled by finding them growing along icy Rocky Mountain streams and carpeting stony natural garden rooms in the High Sierra. Wider travelers have discovered some six hundred members of the Primulaceae, so many that this great genus has been subdivided into thirty sections. Most are found scattered throughout the temperate parts of the northern hemisphere, but a scant handful of southern primroses, best known to us as greenhouse plants, hail from the tropics of Capricorn. In the wild, primulas enjoy an astounding variety of conditions, some clinging to the stern faces of sheer mountain cliffs, others demurely decorating lowland water meadows.

In the garden, however, these beautiful perennials often prove less cooperative, if no less adaptable. I had heard that the rosy, hairy-leaved Japanese Primula kisoana demanded shade and moist, leafy soil, but my original plant sulked in what seemed an ideal spot, sending thickets of runners into the loose coffee bean mulch of the sunny path, where its furry offspring still appear in droves each spring. The white form, said to be even pickier, proliferates happily in its shady bed, but also runs out into the sun, tucking itself between tufts of variegated Japanese iris. An American species, Primula parryi, grows far better in a fairly dry bed beneath an old apple tree than under a weeping willow along our stream, despite its preference for dampness in the wild.

How To Succeed

The keys to garden success with primulas seem to be flexibility–the willingness to experiment with site and soil–and patience. This last is especially valuable, since many wonderful species are most readily available as seed. Fortunately, most primulas are quite easy to raise from seed, which gives you a nice crop of younglings to try in various positions until you learn their preferences. Though exact requirements vary a bit from section to section, most primroses prefer that elusive ideal, a well-drained, moist soil. To this end, we will usually need to amend our natural soils, adding humus for better texture and water retention, compost to buffer the Ph, and grit or coarse builder’s sand to lighten heavy soils and improve drainage. Where summers are hot, stones, mulch, and protective
shrubs will provide cool root runs as well as shade from midday sun.

While all primroses appreciate moisture during active growth, a few, like the Himalayan drumsticks, P. denticulata, tend to rot where winters are wet. To avoid this, primrose fanciers often mulch their plants with stone chips, which works fine in a rock garden but may prove too obtrusive in mixed borders or wild gardens. In such situations, adding an extra helping of grit to the planting pocket and providing shelter, in the form of evergreen shrubs and trees, from prevailing winds will be helpful. So long as the soil mixture is rich enough in humus, dry summers rarely threaten the health of mature plants, though evergreen varieties may turn brown and tatty in a prolonged drought. Where summers tend to be dry, an hydrophilic polymer may be blended into the soil along with the grit (this is not a good idea with primulas that prefer dry winters, however).

Made For The Shade

A further requirement shared by all but a few bog primulas is shade. The amount and kind of shade wanted will vary by genus section as well as by your geographic region, for an alpine auricula that flourishes in almost full sun in my cool Seattle-area garden may need considerable shade to do as well in North Carolina. In any garden, the quality of the shade is important, for few primroses will tolerate dense shade, and all bloom best when receiving plenty of light and air.

The high shade cast by the upper limbs of tall trees in woodland gardens suits many European and Asian woodland species nicely. Most alpine primroses, as well as the subtropicals, prefer full morning and afternoon sun, hiding from the hot midday sun in the partial shade cast by rocks or shrubs. Meadow dwellers (as well as most woodlanders) appreciate the filtered shade found in mixed borders which hold a good percentage of mature shrubs and small trees.

Naturally Good Company

Because they are informal in shape and habit, primulas look more natural in casually mixed company than in formal bedding schemes (fancy auriculas are an obvious exception, but these are nearly always grown in pots). Given the right companions, even exotic species can appear thoroughly at home in American gardens. We can find good company for our primulas among the ranks of native spring blooming wild flowers such as hepaticas, spring beauty (Claytonia virginica), and blue bells (Mertensia virginica). Aroids like our native jack-in-the-pulpit (Arisaema triphyllum) or the southern A. dracontium contribute curious flowers and dramatic foliage to the primula beds, as does the eastern native Mayapple (Podophyllum peltatum).

We can also take a tip from the English hedgerows and mix in sweet violets and lesser celandines (Ranunculus ficaria), of which there are many delightful forms. Mossy saxifrages bloom well in half shade, as will the diminutive Astilbe chinensis ‘Pumila’, with its frilly foliage and mauve flowerspikes. The host of shade tolerant foliage plants such as hostas and ferns blend comfortably with primroses and provide lasting textural interest as well. Evergreen ferns and perennials, perhaps Helleborus foetidus or dainty rosettes of Bergenia ciliata, make good place markers for deciduous Asian primulas like the lacy-petaled Primula sieboldii which have long dormant periods that make them vulnerable to forgetful gardener’s meddling. Candelabras and other bog primulas consort pleasantly with water iris, Canadian tiger lilies (Lilium canadensis), closed and bottle gentians, and skunk cabbage.

Section Vernales

The most adaptable and easy going of the clan are the vernal primroses, a large clan of European garden and meadow primulas which bloom from late winter through spring. These include the chalk yellow true primrose, Primula vulgaris, as well as the nodding yellow cowslips (P. veris) and oxlips (P. elatior) which decorate English meadows and lanes, as well as the bright-eyed polyanthas. All of these thrive in mixed borders, tucked under shrubs or grouped informally along lightly shaded pathways.

Vernal primroses have crinkled, evergreen foliage which suffers in summer drought, but some forms, notably P. x polyanthus, repay summer watering with an autumn crop of flowers, and may bloom straight through a mild winter. In good garden soil, vernals may need dividing every few years. Congested crowns may be gently teased apart into many small plants. The smallest scrap of root that also has a leaf will grow, but the woody, central part should be discarded.

Whose Lips?

Cowslips and oxlips are easily confused in garden settings, where exposure to other vernals has produced lovely hybrids with orange, copper and red flowers. The cowslip (Primula veris, zone 3) has slim stems from which dandle soft bunches of tubular, cupped flowers of clear yellow that smell like spring, each with a loose fitting green calyx. It blooms in March and April, and is unusually tolerant of dry soils. The oxlip (Primula elatior, zone 3) is similar, except that its stems are taller, its flowers are upfacing and lack the characteristic primrose scent.

The true primrose, Primula vulgaris (zone 3), has solitary, wide-eyed flowers, usually soft yellow, on short stems, coming into bloom with the first thaws. Its many forms, both single and double, come in dozens of colors, from vivid reds and blues through faded denim, terra cotta and buff to soft white. Primula x polyantha (zone 3) is a bunch-flowered version with hundreds of variations, including a number of antique forms created centuries ago. Gold and silver laced primulas have a thin rim of white or yellow that encircles and divides each deep-toned petal, while Jack-in-the-green primroses are framed by a large ruff-like calyx. The calyx of a hose-in-hose primrose mimics the flower form and color, looking as if one flower were fitted into another.

Whew!