In this country, window box gardening offers apartment dwellers the enjoyment of container gardening from within or without. If you live in just one room or on a very small property, you, too, can have a window box garden filled in spring with pansies and primroses, in summer with petunias or fuchsias, and in fall with chrysanthemums. In winter, greens and berries, like bittersweet or California pepper berries with pine, give color. English Ivy will provide trailing green all winter if kept out of the wind.
For the best results in a window box gardens, the box ought to be at least three to four feet long but not more than six feet. If larger, it is way too heavy to suspend and secure properly, and it cannot be lifted easily, even by two people. Boxes resting on broad window ledges and on firm porch railings might be eight feet long, but hardly more since moving them becomes too hazardous. Keep to a minimum depth of eight to nine inches, with a width of ten to twelve inches across the top. Of course, lengths must vary according to the window, or series of windows or railing to be decorated with window box gardening.
The most common material for window box gardens is wood. California redwood becomes a neutral gray if not painted, and cypress will last for years. Cedar is recommended, as is a good grade of white pine. Other materials include metals, which are attractive and, for the most part, light in weight. However, they have the disadvantage of conducting heat, thus overheating the soil in your window box garden. Other suitable and durable lightweight materials are plastic, fiberglass, spun glass, and Gardenglas.
If you are handy with tools, you can make your own window boxes of wood, following instructions in pamphlets from your nursery or garden center. Whatever plan you follow, get boards one to one and a quarter inches thick. (Thinner boards will warp and offer little insulation against summer heat.) To fasten, rely on brass screws rather than nails, which in a few years may push out and cause a box to fall apart. To make corners secure, reinforce with angle irons. Be sure to provide enough drainage holes in the bottom for water to pass through freely. Space half-inch holes six to eight inches apart when building your window box gardens.
When boxes are completed, treat the insides with a preservative to prevent rotting. Cuprinol or some other non-toxic material is excellent, but avoid creosote which is poisonous to plants. After the preservative has dried, apply at least two coats of good paint or stain.
Select a color which will not detract from the plants. Traditional dark green is satisfactory, though commonplace, unless you use a tint like apple green. Have in mind the colors of the flowers, especially of plants that trail over the sides. Dark flowers do not show up against dark paint. The same is true of white flowers against light surfaces, as white petunias against white or pale yellow boxes.
To hold window box gardens securely, use bolts or lag screws and treat them beforehand to prevent rusting. Leave an inch or so of space between the window box garden and house for the movement of air. If the box garden is to rest on a terrace or other solid surface, raise them on cleats or set up on bricks or blocks of wood so drainage holes won’t become clogged. Some space under boxes is also important for air circulation, which will dry up run-off water.
When you plant a window box garden, put an inch layer of broken flower pots, crushed brick, small stones or pebbles over the bottom to enable water to escape freely through the openings. Above this, spread a piece of wet burlap or a layer of moist sphagnum moss, old leaves, hard coal clinkers or cinders to prevent soil from washing into the drainage area.
All plants in window box gardening need rich soil for luxuriant growth. Space larger kinds–geraniums, coleus, and fuchsias-eight to ten inches apart; smaller kinds–lobelias, annual phlox, wax begonias, sweet alyssum, and browallia–six inches apart. An eight-inch-wide box accommodates two rows of plants, with the tall ones in back and the low ones along the front. Boxes, ten inches wide, take three rows of plants, tall, medium, and low for edging.
After planting, spread an inch mulch of peat moss or other mulch over the soil to delay drying out and keep weeds in check. In a month, give a liquid fertilizer and follow up with feedings every seven to ten days. Foliage fertilizers can also be applied, but only as a supplement to root feeding.
The choice of plants for window box gardens is limited only by size. Plants over a foot high do not look well unless boxes are exceptionally large. Otherwise, you can grow almost anything you want. For early spring, you might start with Dutch flower bulbs. In cold regions, these can be purchased already grown, or you can raise your own.
Try hyacinths with pansies or early tulips or daffodils interplanted with grape hyacinths, or basket-of-gold and arabis with scillas, chionodoxas, or leucojum. Include some English daisies and sweet-smelling wall flowers, so common in window box gardening in Western Europe. Violas, blue phlox, aubretia, and forget-me-nots are other possibilities.
The favorite plant in window box gardening is the geranium–red or pink for white, cream, or light or dark blue boxes; white for brown, blue, or red boxes. The familiar trailing variegated vinca is excellent with them. Thriving in sun or shade, the vinca needs constant pinching to prevent it from becoming too long. English and German ivies are other trailers for sun or shade. In the sun, low annuals, dwarf marigolds, lobelias and verbenas make nice edgings as does sweet alyssum, in white, purple or lavender. Petunias vie with geraniums in popularity, and any kind can be planted, though the balcony types have the advantage of trailing gracefully over the sides of the window box garden.
In shade that is open to the sky, as on the north side of a house, coleus grows superbly, with white-and-green kinds a handsome contrast for those with red-and-pink leaves. Coleus luxuriates in a rich soil and requires plenty of moisture. Pinch to keep bushy, and to improve appearance remove the spiked blue flowers, unless you especially like them. The Trailing Queen coleus is one of the best.
Other shade-tolerant trailing plants include English ivy and its varieties, creeping jenny, Kenilworth ivy, creeping fig, German ivy, variegated gill-over-the-ground, myrtle, wandering Jew, zebrina, achimenes, chlorophytum, star of Bethlehem or Italian bellflower, and strawberry begonia.
These are just a few hints on planting your window box gardens. Be creative with colors and texture. Window box gardening, so much like container gardening, will become your next favorite hobby.
Happy Window Box Gardening!