Box gardening has extended from such simple beginnings to more elaborate installations. Today entire gardens made of a series of boxes at one or more levels and in varying sizes are often featured on terraces and roofs. Such gardens are especially adaptable to city conditions. On this page we are concerned with the uses of bulbs in such boxes as well as in tubs, pots, and other large containers used outdoors.
Bulbs in window boxes
Because window boxes must be narrow, there is not enough space to permit planting for succession flowering—and so spring-planted bulbs in them must be taken out before summer plants are installed. In this respect they are handled like bulbs used for spring bedding rather than like those planted in permanent flower borders.
Many combinations of bulbs and of bulbs and other spring flowers are practical and beautiful. A single variety of daffodil or narcissus—not the tall kinds—is splendid when combined with forget-me-nots, chionodoxas or trailing myrtle. Tulips and hyacinths are choice and are usually more effective in solid plantings of one colour than when more than one variety is used in the same box.
Hyacinths ordinarily look best planted rather closely together and alone, but tulips can be combined with pansies, English daisies, forget-me-nots, and other low seasonal flowers to achieve most charming effects. If an edging is desired for a box of hyacinths the double-flowered variety of perennial white-flowered Arabis albida is excellent.
Tulips of the early or single or double
types are delightful blooming at the window sill. For a later show, double-,
peony-flowered varieties can be used. The taller May-flowering tulips
are not suitable for window boxes because their height is too great.
If you wish variety in your window box, groups of the lady tulip (Tulipa Clusiana) may be planted alternately with clusters of Scilla sibirica at the back and with snowdrops and glory-of-the-snows set rather thickly in front. Or for colour in a shady spot, snowdrops and winter aconite have charm planted in groups with ferns and primroses. Many other combinations can be worked out and such mixed plantings are of great interest to watch from the inside of the window.
Three bulbous plants stand out above all others as being useful for planting in window boxes for summer bloom: they are fancy-leaved caladiums, tuberous begonias, and dwarf dahlias. All have their limitations. Caladiums will not stand strong sun or whipping winds, begonias resent bright sun and excessive heat and are easily broken by strong winds, dahlias wither under parching heat that comes from bright sun reflected off nearby surfaces. If you cannot provide the conditions these plants need, it is better to fill your window boxes with annuals in the summer than to depend upon bulbs.
Bulbs in garden boxes
Boxes used to form a garden on a roof or terrace offer greater possibilities for varied planting than do window and porch boxes. They can be deeper and wider and thus provide more root room and more accommodation for larger plants.
The boxes may be of different sizes and can be arranged to give style and lend composition to the garden picture. They may be used effectively in a double series—those in back being planted with evergreens where climate permits these to remain outdoors throughout the winter or, in sections where evergreens are not practicable, with privet and other deciduous shrubs. Any of the bulb combinations suggested for window boxes as suitable for spring bedding will be attractive in the foreground boxes. A few well-branched plants of English ivy or creeping myrtle spilling over the front relieves the starkness of box fronts.
For accents, groups of boxes of varying sizes may be built to comprise units —a larger square box containing an evergreen shrub with two lower boxes of just the right size fitted against it to hold bulbs and other flowering plants is a useful combination . . . a triangular-shaped cluster of boxes may form a planting unit for a corner . . . a more complicated pattern of boxes to feature plants in the centre of a terrace. There is great opportunity for creating imaginative box gardens for adaptable locations where beds and borders may not be practicable.
In addition to bulbs favoured for window boxes, others of greater stature may be employed in boxes set at or near ground or floor level. For spring display the taller "Darwin" and other May-flowering tulips are unsurpassed; such items as Spanish bluebells and camassias may be used if the location is shady.
For summer bloom there is a wealth of possibilities in addition to the three items—caladiums, tuberous begonias, and dwarf dahlias—mentioned as most suitable for window and porch boxes. Gladioluses, montbretias, tuberoses, Peruvian daffodils, tigridias, summer-hyacinths, and even lilies come to mind as good possibilities. Indeed with a little ingenuity there is no reason why you cannot grow in plant boxes almost any of the bulbs that are suitable for outdoor beds and borders.
You can plant them in groups among long-flowering annuals to add interest. Oxalises in variety, notably the large pink-flowered Oxalis Bowieana, are exceedingly useful for edgings because they are attractive in foliage and flower and keep blooming for a long time.
Built-in plant boxes constructed as part of buildings vary greatly in size and possibilities. Very often it is advisable to use permanent evergreen shrubs toward the back of them, leaving a space in front for other plants to be added for seasonal colour. In spring these may be hyacinths, tulips, daffodils, and other kinds of bulbs as well as non-bulbous spring-bloomers; in summer they can be arranged in similar fashion to ordinary window boxes.
Built-in boxes and raised beds of masonry constructed away from the building as part of a landscape plan are sometimes used to accommodate potted plants which are changed to provide for a constant colourful display, but this kind of gardening is expensive because it calls for many plants and much growing space to grow them to flowering size. On an extensive scale it is best adapted for stores and commercial and public buildings; in a modest way it can be used by the home owner.
As a matter of fact, to prolong the flowering season with bulbs in a box garden, it is possible to use boxes supplied with good drainage and filled with peatmoss into which potted bulbs in bud or full flower may be plunged deeply enough to obscure the pots. This ensures a continuous display, colour combinations can be changed at will, and plants that have faded flowers or that have been damaged can easily be replaced with fresh ones.
By plunging the pots the soil in them is retarded from drying. It is easily possible to design a box garden that depends for its colour on a display of potted plants—a succession of flowers may be continued until frost without the necessity of taking the plants from their pots, but again it is a little extravagant of plants.
Boxes to be planted directly with flowering plants or boxes in which potted plants are to be displayed must be well constructed. Although many materials have been used, wood is the most popular because of its appearance and comparative lightness, and because it insulates the roots from extreme heat.
Lumber should be at least one inch thick and of a moisture-resistant kind such as redwood or cypress. Even so, it should be treated with a preservative and the boxes should be fitted with removable liners of zinc that have heavily soldered corners and provision for drainage at the bottom.
Cleats are important on the bottom of boxes intended to set on a level surface to permit the drainage and air circulation that prolongs the life of boxes. Where soil-filled boxes are to be left outside over the winter in the north, one side of each box should be slanted to allow for soil expansion caused by frost. There must, of course, be a sturdy means of support for suspended boxes because even a small box is heavy when filled with soil.
Wherever boxes are used, shun that dreadful shade of green paint often used for garden furnishings which is so out of harmony with garden foliage and so beloved by those responsible for the management of many public parks. Most green paints are unsuitable; try neutral tones of other colours.
Culture of bulbs in boxes
The cultural requirements of bulbs planted in boxes are essentially the same as for bulbs planted in pots. Free drainage must be assured, a fertile and porous soil provided, and at no time may the bulbs be permitted to suffer from lack of moisture in the soil. Summer bulbs benefit from weekly applications of dilute fertilizer after they are well established and have filled their soil with roots.
Careful staking may be needed to anticipate storm damage. Faded flowers should be removed promptly. A layer of peatmoss an inch or two thick spread over the soil surface at the beginning of hot weather will keep the roots cool and prevent excessive loss of moisture.
Special provision must be made to prevent boxes planted in the fall with tulips, hyacinths, daffodils, and other hardy bulbs from freezing solid and remaining frozen for long periods in the winter. This does not occur when bulbs are planted several inches beneath the ground outdoors, but it happens easily in a box insulated from the warmth of the lower soil layers and exposed at its sides and tops.
One way of assuring protection is to stand the boxes together on the ground and cover them with a four-inch layer of sand, fine ashes, or sifted earth. If earth is used spread an inch of sand over the boxes before you apply it; this will make it easy to clean off the covering layer in spring without disturbing the soil in the boxes.
Don't bury the boxes too deeply . . . otherwise the bulb shoots will be too long and will break when you attempt to remove the soil covering from them. If the boxes are on a roof, use peatmoss for covering instead of sand, cinders, or soil—it is lighter.
An even better method than burying them with soil is to place the newly planted boxes in a root cellar or unheated ( but nearly frost proof ) cellar. Failing this, you may excavate a hole six inches deeper than the boxes in a well-drained place in the garden and place the boxes in this. Cover it with planks, and, when the ground freezes, add a foot or so of leaves or straw. This method may involve more work at planting time than simply covering with soil, cinders, or sand, but it certainly makes it easier to remove the boxes of bulbs in spring without damage to either boxes or bulbs.
If your plant boxes are of such a quality that you do not wish to bury them over the winter and if you cannot conveniently store them in a suitable cellar, the best plan is to construct one or more inexpensive wooden boxes that will fit inside the regular ones, plant the bulbs in these, and bury them over the winter as previously suggested.
One word of warning regarding mice should be given. They are very fond of tulips and some other bulbs ( but not of daffodils and narcissuses ). It may, therefore, be well to tack small mesh-wire netting over the boxes before putting them in their winter quarters.
Plant the bulbs in the fall at the same time as you would plant the same kinds in the outdoor garden. If they are to be buried outdoors choose a site on the north side of a building or hill so that they will not be encouraged to sprout prematurely. After the surface soil has frozen cover the box with several inches of loose straw, salt hay, or leaves. In early spring uncover it carefully and gradually.
The bulbs you plant in the fall to bloom
in spring are less fussy than most plants about soil fertility. The texture
of the soil, however, is of considerable importance. Don't expect them
to flourish in clay or subsoil that packs so hard that air can scarcely
For summer bulbs a more nutritious earth
is needed. They must manufacture from the soil the foodstuffs they need
for their development and growth ( most of the food necessary for the
production of spring flowers is stored in the bulbs at planting time).
If possible the soil in plant boxes should be changed completely each year. This is rarely practicable in city gardens and not always in the country if a box garden is extensive. However, it is the best plan, and it is particularly important for small boxes that hold but little soil.
If the soil cannot be renewed each year try to change one third of it. Do this by removing all the soil from one end of the box, leveling down the remainder, spreading the new soil on top, and mixing it thoroughly with the old.
Old soil left in place more than one year should be improved each spring by the addition of peatmoss or humus, dried cow manure and fertilizer, and by a liberal sprinkling of lime, all mixed in thoroughly. After mixing leave the surface rough and exposed to the air for a few days before planting.
In tubs and pots
Flower boxes planted and cared for like miniature gardens are not the only plant receptacles used outdoors. Large pots and tubs containing ( usually) individual plants are often employed to beautify patios, terraces, steps, entrances, and formal gardens. Among the plants adaptable for such purposes are a number of bulbs that have foliage and flowers sufficiently bold and massive to invest them with a certain "architectural" character that is desirable in specimen tub and pot plants that are used to add accent and dignity to formal surroundings. Bulbs suitable for this purpose are of kinds that retain interest for a relatively long period and are decorative even when out of flower.
Unexcelled for planting in large tubs and pots is the lily-of-the-Nile, or Agapanthus. It comes in several varieties and blooms for a fairly long period. Its deep green strap-shaped leaves are plentiful and are gracefully disposed. From among them in early summer arise wandlike stems, each tipped with a pointed bud and each attaining an eventual height of three to four feet.
The buds open to release a multitude of star-shaped blue or white flowers disposed in globular heads. The blue-flowered kinds are more pleasing than the white.
Equally as decorative as the lily-of-the-Nile but, because of its earlier blooming season, less adapted to northern gardens are clivias. These have spectacular rounded flower heads of glowing orange which just clear the masses of dark green leaves that are shorter, broader, and stiffer than those of the lily-of-theNile. No better foils exist against which to display clivias than those suggested by McKenny and Seymour who recommend they be "grown in sea-green pots against screens of ivy." They complete their suggestion by saying, "used with orange and blue-green tables and chairs, no other blooming plant is needed on the terrace."
Certain crinums are well worth cultivating in large tubs for blooming outdoors in summer, notably Crinum longifolium, Crinum Moorei, and Crinum Powellii. These noble plants are three or four feet tall in bloom. They have bold foliage and clusters of handsome flowers, pink or white according to variety; they flower over a long season and are well suited for standing on steps or terraces and for associating with other architectural features.
The beautiful bigeneric hybrid between Amaryllis and Crinum that is called Amarcrinum, but should more properly be named Crinodonna, resembles a choice crinum. It has the same decorative value but blooms later, in the North often not opening its beautiful pink "lilies" before an early frost nips the garden. For outdoor display it gives its best service in gardens where winter comes late.
The spider-lily, or Hymenocallis, afford a few kinds adaptable for our purpose. These have good foliage and stout two- or three-foot stalks that carry umbels of richly fragrant, spidery narrow-petaled white flowers. Kinds to try include H. Harrisiana, H. littoralis, H. rotata, and H. galvestonensis.
Rare Elisena longipetala from Peru closely resembles its near relatives, the spider-lilies. It has good-looking foliage and, topping eighteen-inch stems, umbels of deliciously fragrant, fine white narrow-petaled flowers that are attractive over many weeks at high summer.
Although seldom planted in other than garden borders the fragrant Peruvian daffodils or ismenes ( which botanically are Hymenocallis and thus belong with the spider-lilies) make fine specimens when accommodated several together in large pots or tubs—and, because this method of cultivation does not necessitate disturbing the roots at the end of each growing season ( the pots are stored over the winter ), the bulbs thrive and flower more certainly than under the plant-each-spring-dig-up-each-fall schedule that border cultivation demands.
The summer-hyacinth, Galton.ia candicans, responds to the same treatment as Peruvian daffodils and carries stems bearing twenty to thirty pure white bell-shaped flowers to a height of from three to five feet.
If you crave unusual plants for outdoor summer bloom try the curious pineapple-flower (Eucomis) which produces two-foot cylindrical spikes of pale green or almost white starry flowers in July and August. Each cylinder of bloom is surmounted by a crown of green leaves after the fashion of the fruit of a pineapple, which accounts for the common name of this plant.
For a shaded terrace where summer nights are not too warm, by all means grow tuberous begonias in seven- or eight-inch pots. They will give a steady display of gorgeous blooms in a wide variety of colours and forms from June or July until frost.
Not Jo be overlooked as a decorative tub plant is the snake-palm (Hydrosme). The malodorous bloom of the arum relative is borne early in the year, lasts a few days, and is followed by the production of a handsomely marked, attractively divided, solitary umbrella-like leaf that stands on a three- or four-foot stem and spreads its top over a circle that equals in diameter the length of its stem.
Care of bulbs in tubs
All the bulbs mentioned as specimens suitable for cultivation in pots and tubs for outdoor summer use must be protected from frost by wintering indoors in all but the warmest sections of the country. With the exception of tuberous begonias all may remain in the same containers, without repotting, for many years.
Each spring they should be top-dressed with rich soil. The begonias are handled in storage and are replanted exactly as they are when they are grown in pots for indoor decoration. The others are simply stored in the receptacles in which they are growing in a frostproof but cool shed, cold frame, greenhouse, or cellar.
Those that retain green foliage, such as agapanthuses and clivias, must have good light at all times; those that lose their leaves must have light from the time new growth begins in spring. The latter, if stored in a suitably cool and not excessively dry location, will not need watering while dormant. Bulbs that retain their foliage should be kept on the dry side while in storage but should be watered often enough to keep the leaves from wilting or dying.