Naturalized plants require minimum care. They are not weeded in the ordinary sense of the word, although some effort may be needed to curb extremely vigorous and invasive species to prevent them from overpowering their more stay-at-home neighbours. Nor do many other garden routines such as staking and cultivating receive a great deal of attention. The philosophy behind this type of gardening is the assumption that vigorous plants, happily located, can successfully fight most of their battles, and, within limits, this is borne out in practice. The limits are established by the kinds of plants that can be so grown. These vary from location to location.
Among plants suitable for naturalizing are many bulbs, both native and' foreign. Selections may be made that are suitable for planting in lawns and meadows, under shrubbery, beneath solitary trees, and in wooded areas. By their careful use, delightful garden pictures can be created, pictures that will be repeated year after year with a minimum cost for garden maintenance.
Naturalized bulbs are usually set out in a naturalistic fashion. They are disposed in the landscape to appear as if they had arisen from chance-sown seeds and from natural offsets. To heighten this effect, it is normal to select types that will not be too obviously foreign in the landscape and that are not too highly developed horticulturally. It is usual to prefer single flowers to double ones for naturalistic plantings, but this is not an inviolable rule.
Some double-flowered narcissuses can be used with good effect, and magnificent results have been secured by naturalizing great areas with the double-flowered bloodroot. Tulips, except for a very few of the species, one of which is Tulipa Clusiana, are not generally suitable for naturalizing. Most do not persist long enough under American conditions, and most simply do not look right when set out naturalistically—they fail to convince one of their possibilities either as wildlings or as established immigrants.
And this brings us to the only real rule apart from a consideration of the bulbs' ability to establish themselves permanently that can be applied in deciding which are suitable for planting naturalistically. The rule is: if they will look as though they belonged and will thrive with minimum attention, they are acceptable.
Now let us consider a few of the possibilities, and in doing so let us remember that it is not necessary to plant great quantities of bulbs to achieve satisfactory naturalistic effects. Thousands of narcissuses besprinkling a meadow or strewn along the margins of a lake are glorious indeed, but not less lovely are a scant two or three dozen springing up in ones and twos and in small clumps from the grassy floor beneath a white-stemmed birch.
A hundred or two hundred crocuses, especially of a golden yellow kind, will bring sunshine to a slope of lawn that is close backed by shrubs or evergreens. A few tufts of snowdrops planted near a beech are charming; but their charm is not increased proportionately by increasing their numbers.
When bulbs are naturalized in small quantities it is almost always wise to relate them closely to an important shrub or tree or rock evergreen. The two or three dozen narcissuses that are so delightful beneath a birch would be "lost" and ineffective in an open meadow; the one or two hundred crocuses would mean little in a lawn unless they were backed by evergreens or shrubs. It needs a beech, or other featured tree or shrub, to give reason for the few clumps of snowdrops and to direct attention to them.
Bulbs can be naturalized near the house as well as in more remote parts of the garden. It is especially desirable to use the early-flowering kinds there. Some may form part of the foundation planting; others may be established under shrubs and trees and in lawns where they will be seen from the principal windows of the house and from the path leading to its door.
Any planting near a house and particularly near a doorway should have restraint and dignity, qualities that are easily lost by the too-extravagant use of bright colour. This must be considered when bulbs are selected for using with foundation shrubbery.
If azaleas form a prominent part of the scheme, a companion planting of bulbs that flower at the same time as the azaleas is likely to be overpowering, even blatant; in such circumstances use only those bulbs that are well past flowering before the azaleas come into bloom and those you are sure will combine satisfactorily. For foundations favour low bulbs; long-stemmed narcissuses, summer snowflakes, and the like are ungainly in such surroundings.
There are many smaller kinds that are very lovely for the purpose. What is more pleasing to discover beneath the winter-bronzed foliage of a mahonia or a leucothoe that forms part of the foundation shrubbery than the first bright yellow winter aconites nestling in their ruffs of fresh green leaves? Or what is more welcome than the pendant green-tipped glistening-white flowers of the first snowdrops springing up in not too widely scattered groups in the shelter of evergreen shrubs—perhaps appearing through the last remnants of snow?
Scillas or colourful crocuses may be used with good effect in patches on the sunny side of a mugho pine or a yew. Grape-hyacinths seem more choice when set close to Pieris /aponica. Chionodoxas, the blue flowered and white flowered mixed, may carpet the ground effectively near azaleas.
In spring, more than at most seasons, there is emphasis on parts of the garden that are seen from the house windows. Attention is then directed to renewed activity outdoors. Trees and shrubs are principals in the drama of awakening nature in which they play prominent parts. The beauty and effectiveness of many can be greatly enhanced if bulbs are planted naturalistically in association with them.
The Cornelian dogwood (Cornus mas) is one of the first small trees to bloom. Its clusters of tiny yellow flowers are doubly beautiful when hundreds of deep yellow crocuses carpet the ground beneath it. Forsythias are suddenly covered with myriads of wide-open yellow flowers that complement the early blue of grape-hyacinth "Heavenly Blue."
A slightly earlier yellow and blue combination may be had by planting Chionodoxa Luciliae beneath pale yellow corylopsis. Try this chionodoxa, too, below Magnolia stellata—one of the showiest of spring-flowering shrubs or small trees—or plant sweet-scented white narcissuses near a flowering almond or Japanese cherry. Plant second-season hyacinth bulbs of white- and pink-flowered varieties or the white-flowered Scilla sibirica alba to bloom with fragrant lavender-pink Daphne Mezereum. Under Viburnum fragrans, which has flowers the delicate colour of trailing arbutus, establish colonies of blue Scilla sibirica and of its white variety alba.
If, across the lawn, there is a flowering dogwood, white-stemmed birch, a sturdy oak, grey-barked beech, or other featured tree of character, strew crocus bulbs generously beneath it and set them where they fall.
In modern home grounds, closely clipped lawns that surround the home often merge into grassland that is mowed only two or three times during late spring and summer. Such grassland is an ideal place in which to naturalize certain bulbs. Narcissuses top the list of spring-blooming kinds useful for this purpose. Suitable varieties are commonly sold in mixtures especially for naturalizing, but for the best results it is usually best to purchase named varieties separately and to plant them in colonies each consisting mainly of one kind—though gradually intermingling with adjacent colonies at their margins.
To see thousands of narcissuses covering a slope open to the sun, carpeting the sides of a grassy glade under scattered trees, or blooming beneath flowering apples, is an unforgettable experience. These displays should always be visible from a much-frequented vantage-point, if possible from the house windows or from a terrace adjacent to the house.
Spanish bluebells (Scilla hispanica or S. campanulata) and English bluebells (S. nonscripta or S. nutans) are superb for naturalizing in the same manner as narcissuses and thrive in shadier locations. They prosper in partial shade and will bloom even where they get no direct sun. They are not really plants for full exposure although they grow under such conditions if the soil is not too dry.
Spanish bluebells and English bluebells deserve greater popularity. Plant the blue-flowered and white-flowered ones freely but give more thought to locating the pink-flowered variety: you may not like its bluish hue. Spanish bluebells are more vigorous and increase more rapidly than the English kind. These bluebells are well adapted for naturalizing in woodlands—as are many native American bulbs, notably trilliums, bloodroots, and jack-in-the-pulpits, as well as others mentioned in the discussion of bulbs for woodland gardens.
Camassias particularly lend themselves to naturalizing in moist soils in partial shade. Summer snowflakes are excellent in grassy areas in light shade or full sun. Beneath shrubs and trees that border lawns most of the spring-blooming smaller bulbs—glory-of-the-snows, crocuses, snowdrops, puschkinias, and low-growing scillas—can be used effectively as well as the fall-blooming colchicums, the latter grateful for part-day shade. In meadows among low shrubs and at the margins of woodlands many lilies can be made at home. They will delight you in summer with their forms and fragrances. Casual plantings of Lilium canadense, L. tigrinum, L. philadelphicum, L. umbellatum, L. pardalinum, L. chalcedonicum, and L. regale can be used with fine effect in open meadows and at the edges of woodlands; but L. Hansonii, L. Henryi, L. speciosum, and L. superbum are better suited for part-day shade at the woodland edge.
Several alliums are well worth naturalizing. Even common chives, upon which botanists have pinned the somewhat unwieldy name Allium schoenoprasum, is splendid when so used, but not more so than A. Moly, A. Rosenbachianum, or A. tuberosum, to cite but a few of the possibilities that these flowering onions offer.
Summer-hyacinths (Galtonia) in July send
up most un-hyacinth-like flower scapes to a height of three to four feet.
Each bears numerous fragrant white flowers. This plant is fine for naturalizing
and is seen to excellent advantage when interplanted with yuccas.
Of this bulb it is necessary to remember ( as it is of colchicums ) that it produces ample foliage in spring which is apt to look messy when it is dying in early summer. Locate these kinds where you can visit them when in bloom and ignore them when leaves are yellowing.
We have not exhausted the possibilities. In some sections of the country brodiaeas, colochortuses, and erythroniums can be successfully naturalized; in others zephyranthes and cooperias, and there are many others. The criterion is: will the bulbs that it is proposed to naturalize establish themselves, flower each year, and perhaps increase with little care from the gardener?
Planting and after care
When bulbs are to be set out naturalistically, their placement calls for no mean skill. It is easy to get them in studied patches, groups, and rows; but it seems so difficult to plant them as nature does in an arrangement that seems effortless.
Some bulbs are best naturalized in small clumps and as individuals—lilies in a meadow, for example—but even then there should be no regular pattern. In one place two or three or four may be planted closely together; elsewhere single bulbs may be scattered. The distances between individuals and between groups is always varied so that the result is a spacing as casual as that of the stars in the sky—and in some areas in the meadow there should be no "stars" at all.
But most bulbs that are naturalized are planted more densely than this—narcissuses in grassland, crocuses in a lawn, Spanish bluebells in open woodland, grape-hyacinths beneath shrubbery, for example. In such cases distribute the bulbs unevenly by strewing them by handfuls in long sweeping motions so that they fall in elongated drifts and in greater density at one end of each drift than the other.
Allow the planting to thin out here and there to areas without bulbs. See that the drifts and the bulbs are more widely spaced near the extremities of the area that is planted. This is a satisfactory method of copying nature's planting, examples of which can be seen in meadows where wildflowers grow profusely, in communities of trees in woodland—even in the way marsh grasses grow on the sand dunes along the coast.
Because naturalized bulbs remain on location for long periods without disturbance, it is essential that the soil in which they are put be suitable for their particular kind or that it be made so before planting is undertaken. The bulbs must, of course, be set at correct depth and it is simply asking for failure to make holes through three or four inches of topsoil and entomb good bulbs in an underlying stratum of cold clay or impossible subsoil.
The kind of soil beneath bulbs is always more important than that above them, so before naturalizing bulbs, make sure the soil is deep, fertile, and, for most kinds, well drained. Planting may be done with spade, trowel, or a special bulb planter. It is important that the bulbs be placed at the bottom of the holes and that the soil be in firm contact with them all around when planting is completed.
At the beginning of this page it was emphasized that naturalized bulbs need a minimum of care. This is true. Some kinds in some situations bloom regularly for decades with no attention at all, but all benefit from an annual application in early spring of a complete fertilizer and, if planted in grassless places under trees or shrubs, from a light mulch of compost, leafmold, well-rotted sawdust, or peatmoss in fall. Bulbs that must compete with the roots of trees for food and moisture also benefit greatly if they are watered liberally during droughts that occur while they are in leaf.
Never remove foliage until it has died. Naturalized bulbs that become crowded to the extent that the number of flowers they produce is lessened should be dug up, separated, sorted to size, and replanted in newly prepared ground as soon as their foliage has turned brown and before it disappears.