Window boxes are a creative way to add even more interesting, flowering and evergreen plants to the garden. Window boxes are the perfect solution for houses with small gardens, or with no garden at all, as they can be used not only on windows but can also be attached to railings, porches or decks to add color and dimension to these often overlooked areas.
The Window Box
Window boxes come in all shapes and sizes. Most garden centers carry readymade window boxes that can be taken home, installed and planted in a matter of hours. Beautiful custom built window boxes can be made to exact specifications out of many different varieties of materials: new treated wood, reclaimed old wood, plastic, even heavy gauge wire and wrought iron.
As with any other type of container gardening, the boxes should be made or chosen as big as possible, but make sure that the window box is in proportion to the window where it will be hanging. It should be as wide as the window and the depth should be in proportion to the length. There is nothing worse than a window box that is too small for the space. Not only does it not enhance the appearance of the house, the smaller interior space of the box does not support good growth of the plants.
Some window boxes are installed on brackets; others are bolted directly to the bricks and mortar or clapboard. The style of the window box should match the style of the house. A rectangular window box constructed of wood with beveled panels looks perfect in a traditional setting. Cottage styled houses are beautifully enhanced by more casually designed boxes or heavy gauge wire baskets.
Some window boxes come with fitted metal liners that will extend the life of the box by keeping the moisture and dirt away from the wood. Window boxes made of wrought iron, or heavy gauge wire, require a cocoa mat to hold the soil and plants. It is usually better to find one of these boxes with a custom fitted cocoa mat. The cocoa mats wear out after two to three seasons but can be easily replaced. One way to extend the life of the cocoa mat is to line it with a garbage bag cut to fit the liner. Poke holes through the bag to allow for drainage.
The type of soil chosen for the window box might be the most important component in the planting. I have found that lighter potting soils are more successful for use in a container or window box. Use a light potting soil with organic matter and a slow-release fertilizer added for healthier growth. Heavier soils hold too much moisture and can cause the plants and roots to rot. Lighter soils drain more quickly which seems to be more beneficial for the plants. This good drainage is also better for the longevity of the box. If a wooden box is constantly wet it will rot faster than if the soil dries out.
Good drainage is essential for plant health in a window box. Make sure there are multiple holes going all the way down the length of the box. In other words, don’t just have a hole in the middle of the box. If the window box is 24 inches wide, make sure there is a drainage hole every 6 inches. The hole needs to be large enough in diameter to not get clogged by soil debris. However, the hole shouldn’t be so large that the soil runs out. A hole which is the diameter of your thumb is a good rule. It is a good idea to add broken terra cotta shards or large pebbles to slow down the drainage. Place these above and around the hole to slow down the water flowing out of the box. Coffee filters also work well. If the box is planted with evergreen plants that are meant to live for many seasons, check the hole periodically to make sure the roots haven’t grown through and stopped the drainage.
Watering is, of course, essential. There is no hard and fast rule about how many times a week to water the window box. It depends on the sun exposure and the season of the year. Luckily, it is usually easy to test the wetness or dryness of the soil if the window box is within easy reach. Just stick your thumb in to determine if the plants need water. An irrigation drip line is a great convenience. It can be set to a timer to come on a determined number of times a week for a determined amount of time. One very important thing to be aware of is to make sure that large amounts of water are not draining down the house facade. If the house facade is wood, this could cause serious rot problems. If the house is stucco or brick, too much moisture will cause mildew and staining.
Plants need nourishment just like we do. For warm weather plantings, it is beneficial to feed with a granular slow-release fertilizer. These slow-release fertilizers are not efficient during the colder months because the fertilizer is not released unless it is warm. Liquid fertilizers are also good choices to promote blossoms and beautiful foliage. Use liquid fertilizers when the soil in the box is moist. Fertilize after watering so that the liquid fertilizer does not get diluted after a watering cycle. Don’t use a strong solution of liquid fertilizer when the soil is hot and dry. This could burn the plants. For cool or cold weather plantings, use an organic fertilizer such as Plant Tone mixed well into the soil.
Great combinations for spring window boxes
There are so many gorgeous combinations for spring flowering and evergreen window boxes. It is really hard to know where to start. One suggestion is to visit your favorite local garden center and see what appeals to your aesthetic. What textures and colors are you drawn to? Do you want a variety of colors and textures or is it more pleasing to stick to one color and texture? Does an evergreen design appeal to you? Refer back to the Boxwood article in the November 2014 issue of Columbia Metropolitan. Does the large terra cotta container with the dwarf English boxwoods appeal to you? If so, transfer this same design to the window box. If the design is good in the ground, it will most likely be good in a window box.
The good news is that the window box plantings can be changed every season. Experiment with different combinations and take notes. Which combination is the most pleasing to you and enhances your house and garden? Window box plantings follow the same basic rule as container planting. Think of the box as having three layers: tall in the back, medium height in the middle and smaller plants or trailing plants in the front. Spring combinations could also include the addition of spring flowering bulbs such as hyacinths, crocus, daffodils and tulips. Evergreens to consider for the spring box include: dwarf boxwoods, giant liriope or small ornamental grasses. Annuals that work well in window boxes are primroses, violas, dusty miller, petunias, alyssum and lobelia. These annuals are not going to thrive once the temperatures rise in late May and June, so they will have to be replaced with more heat tolerant annuals. Trailing plant choices include Algerian ivy, English ivy and vinca minor.
Successful summer window boxes
Summer can be brutal for plants in window boxes. If the boxes are in full sun, the actual box itself can become very hot and dry, so it is essential to choose tough, reliable plants. Plants to consider as the taller elements in the planting are: Kimberly Queen ferns, giant liriope, carex grass and many of the gorgeous heat-loving salvias. Medium height plants to choose from are: geraniums, lantana, verbena, begonia and ‘Millionbelle’ petunias. If there is room for trailing plants, decide between wire vine, vinca minor or bacopa. Make sure to match the sun and shade tolerance of the plants with the exposure and position of the window box. For example, don’t put a beautiful variegated hosta in a sunny window box. It will be fried to a crisp in a matter of days. Don’t plant a sun loving lantana in a shady box. It will turn into a limp, sad vine by the end of the week! Remember: right plant in the right place!
Herb window box
How wonderful would it be to have herbs right at your fingertips when you are cooking or grilling? Why not add a window box at the kitchen window or on the railing of the back steps and plant it with an assortment of herbs? Some herbs to consider are: basil, sage, chives, thyme, parsley, cilantro, rosemary or any other herb that delights your palate. Here again, make sure the soil is light as herbs do not grow well in heavy, wet soil. The more the herbs are pruned for use, the better they will grow!
Indoor window box
If you are lucky enough to have a large window with a wide interior sill, this is a great place to have an indoor window box. Choose a box that will fix the space and raise it on four ‘pot feet’ to help with drainage. It might be a good idea to have a saucer or drainage pan under the box. Or, if you are really serious about having one, have the windowsill tiled so that moisture is not a concern. A window with morning sun exposure is ideal. Use the same type of light potting soil as you would for an exterior window box, and add granular slow release fertilizer. Tropical or indoor plants will work better in an interior planting. Some plants to consider: ‘Lucky bamboo,’ peace lily, bromeliads, anthurium, dieffenbachia and philodendron.
Spring is right around the corner so start planning your window box by building, buying and planting today. Make a list of the plants for spring, summer and indoor window box combinations when you go to the nursery. Make sure to buy high quality light potting soil and choose the appropriate fertilizer. Window box gardening is a great way for novice gardeners to test their green thumbs, and window box gardens are also small enough for busy gardeners to take care of and will be a cheerful addition to any house and garden. Experienced gardeners can try new plant combinations that they haven’t tried before. Use your imagination and start planning a window box today.
Gardening chores for March:
Garden Centers will be bursting with new specimens this month. Visit the garden centers to get new ideas for your spring and summer garden.
• March is a great month to plant large shrubbery and trees.
• Perennials may be divided and replanted in other areas of the garden or shared with fellow gardeners. Pay particular attention to dayliles. If they become too crowded, they will not bloom as profusely. There are also many plant swaps going on this month. Maybe donate some extra perennials to your favorite group or have one with neighbors and friends.
• Cool season herbs such as sage, garlic, chives and thyme may be planted.
• Complete heavy pruning that was not accomplished in February.
• Shrubs, trees, ground covers and vines should be fertilized now with a balanced, slow release granular fertilizer such as 10-10-10.
• Take over-wintering plants back into the garden on warm sunny days. Bring them back inside if there is any threat of freezing temperatures.
• Wash out and scrub any empty containers that you plan to plant this spring.
• Check hoses to make sure there was no damage done in the cold winter months.
• Audit irrigation system and re-set timer.
• Check outdoor lighting and replace any burned out bulbs.
• Clean outdoor porches and furniture in anticipation of the warm months to come.
• Visit local garden centers to learn about new plants and products.
• Pressure-wash any slippery outdoor hardscape areas.
• Drive around Columbia to see our beautiful gardens coming back to life!