Planting the Plantsman’s Garden: 2 — Herbaceous Perennials

Perennials are marvelously eventful. Some of them spring out of the ground with the advent of warm weather, grow rapidly to prodigious heights, and flower for half or more of the time they are above ground.

It is an axiom that serious gardeners love plants for themselves. They want to possess them, to grow them, to look at them, and, more generally and simply, to have them around. Here I am concerned with that aspect of gardening that consists in growing these plants well and displaying them well in association. Therefore I should like to put aside for the time not only such peripheral matters as stones, statues, ponds, and gazebos, but also the various functions that plants may serve as privacy screens, as settings for houses, and as something more orderly than nature usually provides by way of groundcover. It is no doubt true that plants may serve certain useful functions and be beautiful at the same time, but I want to talk about planting as we would about music when we go to a concert and simply lend ourselves to the performance. In other words, I want to reverse the usual order that starts with garden design and ends with planting. If we begin instead with plants and their associations, perhaps we can then work back to the scheme of the garden as a whole with new insights.

In the last issue I noted that William Robinson and Gertrude Jekyll initiated a modern style of gardening using an abundance of plants informally disposed, which they thought of as “natural.” Their use of this word has come under scrutiny and various substitutions have been suggested, such as “in the natural style” or “in the language of nature.” I think we could clarify this matter by saying that the garden plants we buy or propagate have necessarily been torn from their origins in plant communities in nature and that we try to arrange them in our gardens in a way that will give them new homes — an art whose final aim is to appear artless and “natural” in that sense.

Double herbaceous borders at Bampton Manor, Oxfordshire. Photograph by Christine Rosmini.

Double herbaceous borders at Bampton Manor, Oxfordshire. Photograph by Christine Rosmini.

Herbaceous Plantings

Earlier in this century the heart of the English garden was the herbaceous border, an elaborate arrangement of non-woody flowering plants, often well over two hundred feet long and about fifteen feet — or sometimes much more — deep. As brought to fruition in some of the famous gardens, this represented the most tenuous and difficult project in the history of gardening. To be successful, the border had to fulfill a staggering number of conditions. It had to present, in succession, a satisfying and sizeable number of plants in full flower over a considerable period of time. All the plants had to be arranged so as to be visible from the front of the border, which was usually a lawn path. As the plants came into flower they had to be compatible with their neighbors and with the border as a whole. Above all, the entire border had to present a diversity of plants with a unity of overall effect — from every angle of vision it had to be a “living picture,” as Miss Jekyll was fond of saying. And all this was just a beginning. The great borders also had to qualify as distinctive works of art; they had, in other words, to offer the viewer plant combinations and, if possible, plants themselves that could be found nowhere else.

Some gardeners tried to plant a border that would put on floral displays from spring to fall, but Gertrude Jekyll considered this feat impossible. Her own border was at its best in late summer and was considered satisfactory from July until October; other parts of the garden were used for spring and summer displays. Even so, a considerable amount of tinkering was involved in keeping the border going for three months. Many and devious were the contrivances used. One of them might be called plant substitution. Thus, if we want to grow Gypsophila paniculata with its starry flowers in magnificent heads four feet across, we have the problem of four feet of blank space until this great flowering event occurs. Accordingly, in this space we grow oriental poppies. They, however, rather soon leave brown seed heads; therefore we also grow nasturtiums in this plot to cover the “greater part of the brown seed spray.”

Another device used we might call successive plant hiding. Thus, the bare stems of delphin­iums are covered by the everlasting pea, and, when this goes out of bloom, Clematis x jackmanii takes over, followed in turn by Clematis flammula. And none of this is simple. Miss Jekyll explains:

It must not be supposed that they are just lumped one above another so that the under ones have their leafy growth smothered. They are always being watched, and, bit by bit, the earlier growths are removed as soon as their respective plants are better without them.

Still another trick is to pull down plants whose natural habit is tall and upright to cover the plants that are past flowering. Finally, when all else fails, it was considered wise to have a stock of perennials growing in pots for rapid transplantation to the border. In no event should holes be allowed to threaten the totality of the “living picture.”

Bay of perennials with Macleaya  cordata. Author’s photograph.

Bay of perennials with Macleaya cordata at left and Salvia uliginosa, Phlox maculata ‘Miss Lingard’ and Linaria triornithophora. Author’s photograph.

Of course, keeping the border going in summer was only a small part of what had to be done. Elaborate procedures were devised, many of them by Miss Jekyll, for staking plants that needed support in a way that would not show, and this was done in late winter. The habits and requirements of all the plants had to be known well. It was important to know, for example, the volume of roots required for maximum performance. Eryngium ‘Violetta’ needs to be left undisturbed for five years or more to give rise to a showy clump of flowering stalks. MacIeaya cordata (Bocconia cordata), on the other hand, spreads widely and most of its roots will need to be dug up and thrown away every year. All this is in addition to soil preparation, top dressings, mulches, drainage preparations, and other gardening practices that will guarantee maximum healthy growth of a close planting of large-scale plants.

Difficult and intricate in both its inception and its maintenance, the perennial border was strictly for intrepid gardeners. Said Miss Jekyll:

Good gardening means patience and dogged determination…. Those who do not know are apt to think that hardy flower gardening of the best kind is easy. It is not easy at all. It has taken me half a lifetime merely to find what is best worth doing, and a good slice of the other half to puzzle out the ways of doing it.

In the course of time, ingenious British gardeners found many ways to heighten the origi­nality and elegance of their borders. Differing placements of plants according to size were attempted, sometimes with signal results. Very early in the history of the border it was realized that a simple scheme using low plants in front with a gradual rise to very tall ones in the rear could be improved upon. A more compelling form and apparent artlessness could result from placing an occasional bold plant in front, from massing of tall plants here and there to prevent a too-uniform skyline, and from carrying a carpet of low plants all the way from the front to the rear in a few places. Considerable attention was paid to the form of plants — whether, for example, they sent up flowers in rounded masses or in spikes. Sometimes tall grasses or colored foliage shrubs would be introduced to create a backdrop for certain flowers or to give a formally bold effect.

Most important, however, was the arrangement of plants according to flower and foliage color. Miss Jekyll’s most influential work is a volume that covers many aspects of gardening, but is symptomatically entitled Colour Schemes for the Flower Garden. Here, with a few omissions, is how she describes the color scheme of her own border:

At the two ends there is a groundwork of grey and glaucous foliage. With this, at the near or western end, there are flowers of pure blue, grey-blue, palest yellow and palest pink. The coloring then passes through stronger yellows to orange and red. By the time the middle space… is reached the color is strong and gorgeous, but, as it is in good harmonies, it is never garish. Then the color strength recedes in inverse sequence through orange and deep yellow to pale yellow, white and palest pink; again with blue-grey foliage. But at this eastern end, instead of pure blues, we have purples and lilacs.

Today we can still see in England a number of beautiful borders with pronounced color themes. One has only blue and yellow flowers, another simply eliminates all strong colors, still another consists entirely of warm colors. There are carefully blended borders and others with deliberately contrasting flower tints. It is true that perhaps an equal number of famous borders are not based on such color themes, but even here I have noticed that plants have been carefully placed among their neighbors to display their colors to advantage. The effect of these borders as a whole is that of a giant Victorian bouquet, a wild and seemingly careless arrangement of plant forms and colors that in reality demands extreme care. Anyone who gardens can see that none of this is easy. A great many years often went by before most borders reached the degree of perfection their creators were seeking.

Such is, or perhaps I should say was, the English perennial border. I have tried to describe it at some length for a number of reasons. First, some gardeners still plant borders of this kind. But far more important here is the fact that the English border was the last great garden form in our history to have won wide acceptance, and the surviving examples are works of almost incomparable beauty. There are many reasons, however, why I cannot in all honesty urge gardeners today to set out on the laborious path outlined by Gertrude Jekyll. In part this is because they are apt not to have the time and resources to carry this great art form to new heights and the results therefore would be likely to fall short of achieving the magic and charm needed to be truly successful.

There is another more complicated reason to search for other ways of using perennial plants in the garden. For all its compelling beauty, I find that the grand border subordinated plants too much to overall effect. In the case of those plants that flower profusely but otherwise are of no interest, little is lost. But many superb herbaceous plants from the prairies, low mountains, valleys, and streamsides of the temperate world have great beauty of form as well as flower. They deserve better than simply to serve as ingredients in a bouquet. Today we must find new homes for the large lowland flowering plants that most of us find such an essential ingredient in our gardens.

Herbaceous perennials, together with large deciduous bulbs and similar grasses, are the most difficult of all plants to site. Because of their long-lived roots or other parts below ground, these plants need more or less permanent homes. But since at certain seasons their parts above ground are small or nonexistent while at others they are sizeable, considerable foresight and planning are necessary to visualize their effects both at maturity and in dormancy. We do not like bare spaces in winter here on the Pacific coast where gardens are enjoyed year round, and in summer a sudden growth of lush foliage risks shading out neighboring plants.

The easiest of all gardens to maintain is one made up of long-lived, mostly evergreen, well behaved shrubs. Such a garden needs a minimum of pruning, weeding, and cleaning and no culti­vation at all; it is, however, comparatively uneventful even when some of the shrubs are briefly showy in flower. Perennials on the other hand, need a maximum of pruning, weeding, and cultivation, even sometimes staking and additional managing, but they are marvelously eventful. Some of them spring out of the ground with the advent of warm weather, grow rapidly to prodigious heights, and flower for half or more of the time they are above ground.

This is, of course, a somewhat simplified picture. There are some evergreen perennials that behave more like shrubs and vice versa. It is, however, a useful image to keep in mind when allocating spaces. We need to decide, and decide quickly, how much of the garden we wish to give over to plants of a highly eventful character and balance this against our resources for maintenance. Having accomplished this imaginative exercise we can then find places in the garden to site perennials that will show off these plants to advantage and give us many of the qualities of the great border with far less labor.

Perennials in Bays Among Shrubs

Planting perennials in small groupings in a number of plots among shrubs and small trees seems to me one way of managing the problems associated with the grand flower border. Because of their smaller number, it becomes vastly more feasible to imagine how certain associations of plants will look at maturity. Also, many of the problems of maintaining a continuous succession of flowers will simply be solved by assigning shorter periods of duty to each plot; thus, when the full flowering of one such bay is diminishing, another somewhere along the path is preparing to take over. With enough care, no special contrivances other than dead heading will be necessary to keep these plots looking garden-worthy.

Achillea ‘Moonshine’ with a background of Salvia nemorosa. Photograph by W.G. Waters.

Achillea ‘Moonshine’ with a background of Salvia nemorosa. Photograph by W.G. Waters.

What we are to imagine is a continuous series of flowering events throughout a larger area of the garden to replace the concentrated show Robinson and Jekyll demanded. The drama of these events, of course, depends upon our skill as gardeners — whether, for example, we find the most striking combinations or site our enclaves for maximum effect. Even the sizes and shapes of the plots we create are important.

In a garden bay at home, it was decided to plant only perennials that flower in late summer. Spring and early summer interest in this part of the garden is already provided by nearby flowering shrubs and trees, the two clematises that have been trained over supports, and the mixed pathside plantings above and below our plot.

The primary objective is to show off Artemisia lactiflora, a beautiful and statuesque but untypical member of its genus. This plant grows to over five feet, has dark green foliage topped by graceful panicles of creamy-white flowers, and needs semi-shade to perform well. To allow the full stature of the plant to be appreciated, it was surrounded with much lower, blue-flowered geraniums, for which this exposure is also ideal in our climate.

In the foreground of this arrangement is a large mound of three plants of Nepeta gigantea. Probably a hybrid, this looks like the plant often sold in nurseries as Nepeta x faassenii, but it grows twice as high and wide (three by three feet). Beyond this mound and well to one side of the artemisia is perovskia with spires of light blue over silvery gray, finely divided leaves. Beyond this again is the tall, late-flowering Campanula latifolia. Off to one side is a group of Phlox paniculata ‘Norah Leigh’, which has delicate pink flowers and equally delicate cream and pink variegated leaves.

Between the phlox and the artemisia is the big, globular, soft yellow thistle, Centaurea glastifolia. On the other side of the artemisia is the tall Rudbeckia nitida ‘Herbstsonne’, which has primrose yellow flowers with green centers. This would also be a good place to site the giant annual rudbeckia, Rudbeckia maxima, with its magnificent display of thousands of small black-eyed-Susan daisies.

The only other important part of this planting is a stand of Aster x frikartii ‘Moench’, with its great mound of blue asters produced over a long season. There are a number of other single, smaller plants not shown in the drawing for the sake of simplicity. One is Potentilla ‘Gibson’s Scarlet’, which blooms sparingly over a long period, and there are a few plants of Aquilegia longissima, which flower in the spring and whose foliage seems to survive the crowding of larger neighbors.

Of course, this late-flowering enclave is not bare in spring and early summer. The plants chosen for it have good foliage, and the plot forms part of the general leafy garden background until it flowers.

Recently planted border in the author’s garden with alstroemerias in foreground. Photograph by W.G. Waters.

Recently planted border in the author’s garden with alstroemerias in foreground. Photograph by W.G. Waters.

Just beyond our perennial enclave is a patch of Helleborus foetidus for late winter flowers, a stand of Evansia irises for early spring, and alstroemerias for late spring and early summer. There is a succession of flowering shrubs from Daphne bholua in mid-winter to Hydrangea aspera (H. villosa) in late summer.

The deliberate stage management of the plot I have just described is not typical of the garden as a whole, as we can tell if we enlarge our vision to include the neighboring trees, shrubs, and other plants. If I ask myself how these plants came to be where they are, the answer has perhaps more to do with their well-being than with any purely aesthetic considerations. Soon after publication of the works of Robinson and Jekyll a schism among their followers became apparent, dividing those whose primary concern was “the garden beautiful” from those who, above all, wanted to grow a range of plants to perfection. E.A. Bowles was one of the latter, and in 1914 he wrote:

I fear I am a little impatient of the school of gardening that encourages the selection of plants merely as artistic furniture, chosen for color only, like ribbons or embroidery silks. I feel sorry for plants that are obliged to make a struggle for life in uncongenial situations because their owner wishes all things of those shades of pink, blue or orange to fit in next to the grey or crimson planting….

In my own case, my habit of trying important new additions to the garden in three locations to give the plants a fair trial, more or less precludes total control and unity of aesthetic effect. This says nothing of the anarchy caused by planting out seedlings of shrubs and trees I cannot even find described in the books. All this does not mean, however, that plants are placed just anywhere among their neighbors. Many agonizing decisions are made in an effort to combine a desire for experimentation with a longing for a harmonious garden. Speaking of his own method, E.A. Bowles writes:

The distribution of plants in this garden has been governed chiefly by a sort of extra sense that seems to be developed by many enthusiastic gardeners, a sympathetic understanding derived from a new plant’s appearance only when the power is perfected….

In general I would say that it is because so much of the garden is planned only in this intuitive way that I welcome the occasional opportunity to try self-consciously to bring off a well planned coup, and, of course, the herbaceous perennial with its varying heights and floral mass, is the ideal plant for this purpose.

Another, somewhat smaller bay, also given over to late-flowering plants, is ideally situated in front of a sizeable group of Melianthus ma­jor. This much maligned shrub forms a beautiful background for herbaceous plants with its great, jagged, blue-green leaves that themselves have the look of a giant perennial. Here have been planted several of a pink form of Sedum spectabile, which has foliage of the same blue-gray and whose large, flat flower clusters remain beautiful in the autumn when they have darkened to a deep rosy brown. Behind the sedum are a few plants of the late-flowering Cimicifuga ramosa with, in front of these and among the sedums, an aconite, Aconitum carmichaelii (erroneously known as A. fischeri). These are all lovely and majestic plants.

In front of this display is a brilliant blue patch of late-flowering Ceratostigma plumbaginoides. These flowers provide the climax to a long season in this part of the garden, where there are also early bulbs, early summer flowering lilies rising out of the melianthus (which is cut back severely every spring), and a somewhat later-flowering dierama off to one side.

In future contributions I shall continue to explore the planting possibilities of herbaceous perennials before going on to their close cousins, the annuals and biennials.