Gardeners in areas with summer-dry climates who are seeking plants needing little or no irrigation need not depend upon natives. In his travels in Mediterranean countries the author, a partner in Western Hills Nursery, has learned the special merits of many plants from that region and their value to gardeners in the West. Brooms and rock-roses, many of them Mediterranean plants of particular ornamental value for summer dry gardens, were discussed by Lester Hawkins in two earlier issues of Pacific Horticulture — those for Summer and Fall, 1978. This contribution will be continued in our next issue.
To begin with, let us imagine a walk planted on both sides with a deep border of Mediterranean plants. Many of the plants are famous for the fragrance of their foliage and among them are rue, wormwood, hyssop, lavender, sage, and other herbs. Most are almost equally well known for the distinctive color of their foliage, which varies from almost pure white through shades of blue and gray to deep green, with an added few that are golden or purple or red. Also pleasing is the texture of the leaves, which can be fine and heather-like, as in santolinas and thymes; lacy, as in some artemisias, or deeply woolly as in Phlomis fruticosa. And then, of course, there are the flowers. Almost all year something is in bloom here in Occidental and, at some seasons, the spectacle rivals that of the English perennial border. Unlike the latter, however, this garden is basically evergreen — as befits our climate, for we certainly do not want our plants to hide underground just when the rest of nature is flourishing.
If I were to use the old classifications inherited from England and eastern United States, we would have to say that what I have been describing is indeed part perennial border and also part herb garden and even partly a shrubbery. But we can ignore these formulas as old-fashioned, absurd, or, at least, not applicable to us. In colder climates the perennial border lies dormant all winter like the rest of nature and comes into its own only in high summer and fall. In winter and early spring — prime seasons for us on the Pacific Coast — it is nothing.
Again, many of our plants are traditionally known as herbs. The Royal Horticultural Society’s Dictionary of Gardening describes an herb garden as “a separate ornamental garden, often of formal design and based on early knot gardens or parterres in which herbs were grown in Tudor or Elizabethan times. These were usually edged with shrubby box, lavender, lavender cotton, winter savory, hyssop and so on, which were kept closely trimmed.” What an idea! Here are plants that in nature like to spill, spread over rocks, form marvelous natural domes, or grow into and twine around other plants, all of which is half their charm. Therefore we must erase this image of the herb garden, since we certainly have no intention of mutilating these plants to fit some geometrical or architectural fancy.
And, of course, the old formulas for shrubbery and herbaceous borders do not apply. Since our garden is largely evergreen and consists almost entirely of Mediterranean plants with the horticultural characters we want, the plants may be herbaceous, sub-shrubby or entirely woody, without distinction.
However, enough of what it is not. Let us return to our path through charming, colorful and fragrant plants from the sunny hills bordering the great inland sea. Of the many thousands of flowering plants in this region, we have selected for our purposes those that have obvious attractions of form or flower or foliage or fragrance (and sometimes all four) and that are also good garden subjects in more practical ways. (They are dense and suppress weeds, or they are at least relatively compact — not tall and rangy, and they do not become pests by reseeding or running at the root.)
But let us start again and try to describe our walk. On either side in the foreground are low, somewhat spreading plants such as Lithodora diffusa, Genista lydia, Anthemis cupaniana, middle-sized plants of Dianthus, Erinacea pungens, and the larger acantholimons with perhaps a few tufts of Iris unguicularis. Since these plants like to grow among and sometimes spread over rocks, there will also be a few flattish stones among them. Behind these, for the most part, will be somewhat taller plants (although only for the most part; we shall follow no rigid scheme of low, medium and high, but shall consider only that the lower ones do, after all, have to be seen.) These are dwarf forms of Lavandula angustifolia (L. officinalis), Origanum dictamnus, Dianthus superbus, Onosma frutescens, and Hypericum olympicum. From this point we ascend through plants of the height of Euphorbia rigida and Hyssopus officinalis to the taller Rosmarinus and Artemisia arborescens to a background (if there is space) of larger shrubs and small trees.
I have included plants often thought of as rock garden subjects, but I have carefully omitted alpines proper and tiny buns that would soon be overrun by more rampant neighbors. High alpines require the special conditions that only a rock garden can supply, and they are never seen in nature around the shores of the Mediterranean with the other plants — the lowlanders and year-round performers — on my list.
Construction and Care
All the plants we shall consider are easy enough to grow, but they do require drainage. The shores of the Mediterranean are for the most part rocky. If the basic soil is heavy and apt to become waterlogged, it is wise to mound up the areas to be planted to the height of a foot or so. Crushed rock should first be worked into the substratum with, perhaps, gypsum, and the mounding should be done with light topsoil or a sand, firbark and topsoil mix. We should make certain that water runs off readily on all sides. The mounding, incidentally, serves aesthetic as well as practical ends by raising the foreground plants to a level where they can be more easily seen and from which they can drape downward onto the path instead of horizontally across it.
Our Mediterranean garden requires only the simplest care. All but the foreground plants have excellent weed-smothering properties, and the plants should be allowed to grow together as they would in nature for this purpose. The practice of separating all plants with a neat border of bare cultivated soil has never been to my taste. A far better rule, I think, is never to cultivate (which brings up weed seeds.) If the charming natural flow of plants threatens to become an unsightly tangle (there is a fine borderline between the one and the other) the condition is best cured by pruning.
All the plants described here are drought resistant and will grow in the coastal areas of California with little or even no irrigation. In warmer areas deep watering once a month is usually sufficient. We should remember that, while the climate of the Mediterranean is very much like California, most of the areas from which these plants come receive a scattering of summer rain and have a somewhat less prolonged dry season than our own. This may account for the fact that virtually all the plants described have good garden tolerance, that is, they will take regular irrigation provided drainage is adequate.
The kind of path I have been trying to describe can serve a variety of functions within a larger landscape. I first used its prototype as a substitute for an herbaceous border on a dry hillside otherwise planted with California native shrubs. In this case, every plant had to provide color, either from flowers or foliage. The herbal fragrance proved to be an added bonus; I had not given it a conscious thought. It was only later that I began to ask myself if this wasn’t the answer to one of our gardening problems. The brilliant silver of some artemisias under our clear skies and the smell of lavenders in our dry air can, after all, be very special features in our gardens.
In the descriptions that follow I shall try to list what I have found to be the best plants and the best forms of them for the Mediterranean garden. Selecting the most appropriate of these and combining them into a path that is restful or exciting, quietly charming or impressive, is, of course, part of the art of gardening for which there is no recipe (and for which I hope we wouldn’t want one). We do, however, have the example of nature and our freedom to experiment, (and if one attempt fails, to transplant and transplant again).
There are almost too many candidates for the foreground of our path. The hills around the Mediterranean are usually low brushland (maquis) or stony wastes (garigue) that still manage to harbor a very large number of desirable and low growing garden subjects (Erinacea pungens, for example, or Genista horrida). If we raise our sights to the surrounding mountains and include those alpines of the right breadth and stature that will do well in ordinary garden conditions at low elevations, we shall at least double the number of possibilities. Here I can only describe a few that I have found to be accommodating and durable all-season performers for Pacific Coast gardens.
Of the sizeable number of mat forming achilleas, I have found the best for our purpose to be Achilles umbellata, with deeply-lobed white felted leaves, A. ageratifolia, with very finely toothed, almost entire narrow gray-green leaves, and A. clavenae (A. argentea), with deeply toothed silvery leaves. All three plants creep around rocks without ever becoming unduly invasive; all remain perfect silver or gray cushions throughout winter; and all are reasonably resistant to the effects
of heat and drought. Their flowers, which are of far less importance than their foliage, are white daisies on short stems, very showy for a brief period in spring. Achillea tomentosa makes a low, ferny green mat with yellow flowers, somewhat like a miniature of our common yarrow, A. millefolium. It is attractive, but I have found that it takes neither heat nor drought nor winter wet as well as the first three on our list. A. rupestris, from southern Italy, is praised by Farrer as the most beautiful in flower of all the low achilleas; it has green entire leaves and masses of white daisies on six-inch stems, but Farrer notes that it also suffers from the effects of dampness in winter.
Many aethionemas make excellent path-side plants. All have an abundance of pink flowers in spring, and tiny, bluish evergreen leaves on spreading plants that tend to be somewhat woody at the base. By far the best of these that I have seen is Aethionema grandiflorum from Lebanon, which has flowers of a sparkling bright pink, much larger than the more deeply colored but somewhat dingy A. ‘Warley Rose’.
Alyssum murale (A. argenteum) is an upright, silvery, thinly clothed shrub to about eighteen inches, with umbels of yellow flowers. It is a little high for the foreground but I include it here because it seems so well placed growing out from a rock next to a path. The hills and mountains around the Mediterranean are rich in alyssums, most of which form small tufts for the rock garden, but others would be more useful for our border if we had them: Alyssoides creticum (Alyssum creticum), for example, has the habit and flowers of the well-known Aurinia saxatilis (Alyssum saxatile), but is an astounding silvery-scaly plant.
Anthemis cupaniana is one of the best path-side plants of all, the perfect foil for a background of lavenders and euphorbias. Here I should quote Farrer; “Anthemis cupaniana is a treasure from Italy, perfectly hardy and of the greatest value, though not by any means small or dainty. It forms a vast decumbent mass often a yard or more across and perhaps six inches deep, of fat shoots embedded in masses of neat, ferny foliage, rather plump and gray and pleasantly aromatic. From these… springs an unceasing profusion of large and brilliant showy Marguerites carried well aloft, some six inches or more above the mass. This beauty seems indifferent to sun or shade, heavy soil or light.” Anthemis nobilis, chamomile, on the other hand, is an invasive pest that should never be planted unless in an area with solid masonry borders, but there are a number of equally ferny, better behaved mats from Crete, Sicily, and other sunny places, some of them silvery, that need to be brought into cultivation.
Arenaria montana is not, as its name suggests, a high alpine: it is really from the foothills and lower mountains of Spain. In time it forms a large, prostrate, evergreen mat covered solidly, like snow, with pure white flowers for a long period in spring. One great advantage in growing plants of this kind along paths instead of in the rock garden is that here they can be given room to spread to a yard across without injury to delicate and diminutive neighbors.
Plants of the ordinary Armeria maritime from seacoasts almost throughout the northern hemisphere, including the Mediterranean, make perfectly foolproof low tufts of grassy foliage that are always pleasing, with pink flowers appearing for long periods. Better, however, is Armeria leucocephala (A. corsica), a somewhat smaller plant with brick-red flowers.
Artemisias, unfortunately, will have to be omitted from our foreground. All the low-growing species I know of are deciduous, and most are not from the Mediterranean.
Asteriscus maritimus (Odontospermum maritimum) is a most attractive, silky-woolly dwarf shrub with neat, upstanding grayish leaves and large yellow daisies surrounded by leafy bracts. This plant grows not only near the sea but also in dry places inland on both the African and European sides of the Mediterranean. A similar, but much larger and more tender shrub is Asteriscus sericeus from the Canaries.
Ballota pseudodictamnus, from Crete, is a charming and peculiar white-woolly evergreen perennial to two feet, narrowly upright in habit. I list it among the foreground plants because it should stand alone, isolated from other plants of its height. The leaves of this deeply felted sub-shrub are attractively veined and somewhat scalloped and cupped, like shallow seashells, and the tiny flowers, borne in the leaf-axils, are surrounded with woolly chartreuse bracts.
Campanulas, of course, abound in the Mediterranean. Everywhere there are bell-flowers resembling Campanula rupestris, or variants of C. glomerata, or, often, twining through lavenders, frail plants of the C. rotundifolia kind. Campanula isophylla is a native of sea cliffs near Genoa, and C. portenschlagiana grows among rocks around the Adriatic. Beside our path is a good place to grow these showy plants that are too large and a little too ordinary for the rock garden (which should be reserved for C. raineri, C. zoysii, C. morettiana, and other rarities). They are valuable, also, for providing flowers when the season for most of our low plants is over.
Chrysanthemum atlanticum, from the Atlas Mountains, seems perfectly happy at low elevations. It is another mat of ferny foliage with wide-spreading masses of white daisies, but is altogether smaller than Anthemis cupaniana.
Convolvulus sabaticus (C. mauritanicus), from North Africa, sends out large violet-blue flowers at ground level all summer; a single plant will grow to five feet across. Convolvulus boissieri (C. nitidus) from middle elevations in the Spanish Sierra Nevada is supposed to be even better, with silvery foliage and rose-tinged white flowers, but has, so far, not succeeded here, perhaps because of our excessive winter rains.
For cytisus and cistus please see my descriptions in issues of Pacific Horticulture for summer and fall, 1978. Most rock roses are too large for our foreground planting, but any number of dwarf brooms are ideal.
Daphnes are found here and there in small localities all across the northern Mediterranean countries. Here in Occidental we have found Daphne cneorum and some cultivars, and Daphne collina perfectly faithful plants in full sun and given little water. Sometimes one will die from no discernible cause, but, if there are two or more plants in the garden, there is no great cause for concern. As Farrer once noted, you can cosset a daphne and give it every ideal condition only to find it will not grow for you, and then discover that your neighbor has simply planted one out in ordinary soil among his bedding plants, and it is thriving. Therefore, there seems no reason not to plant one or two of these loveliest of low shrubs along our path. For its fragrance alone it is worth a place. It is perhaps worth noting that, on the island of Euboea, I saw a wide low shrub, a mass of interlaced branches that I now know to have been Daphne jasminea, one of the most beautiful of all daphnes. There it was, thriving in a twenty-five-inch rainfall area with very long hot dry summers. Perhaps one day we shall succeed in acquiring and growing a plant of it.
Dianthus are not only excellent flowering plants for our purpose, but they also provide low mats of blue or silvery foliage the year around. The best of these I have found to be Dianthus gratianopolitanus (D. caesius) and D. plumarius and their hybrids with their very blue foliage and large deep pink flowers smelling of cloves. Unfortunately, neither is strictly Mediterranean; the center of the best dianthus seems to be Central Europe and the Balkans (and, of course, the higher mountains). Those I saw in the Mediterranean hills were tall, rangy plants, only one of which, Dianthus fruticosus, shrubby, with a picturesque gnarled trunk, seemed worth introducing.
Dorycnium hirsutum is a charming very white and very woolly spreading pea shrub which mounds up to a height of about eight inches and will, in time, grow a yard across. White flowers flushed with pink appear here and there in this soft mass of foliage over a long period.
Erinacea pungens is perhaps the best of a number of very spiny low hedgehogs that have survived the ravages of goats and drought on hot rocky hillsides (the others include Poterium spinosum and Genista horrida). The spines of Erinacea (it is a monotypic genus) are dense and a shining silvery green. The flowers are large, violet blue, and papillionaceous, but their most attractive feature is the large, fluffy and silvery calyces among which they are set. The plant is slow growing but a number of them placed in a clump will hasten the time when they can be enjoyed.