Deck Gardening

Wood deck is a very common addition in our residential home. It is our extended living space.

You can grow flowers and vines in pots, harvested vegetables from trellises, trimmed a topiary tree rose and even enjoyed a small water garden. Blooms from a miniature tropical water lily closed each evening at dusk.

The same effect can be achieved on your deck, bringing the garden from the yard to your fingertips, complete with fragrance, color and even wildlife.

Deck gardening does present a unique set of challenges, however. Wind can topple potted trees and desiccate their foliage, watering is a constant worry and when it's time to relax even avid gardeners need relief from insistent late afternoon sun.

All those problems can be solved, of course, and must be solved for a deck or balcony to be transformed into an inviting urban oasis.

We started with a few annuals, and quickly discovered that watering becomes a twice-daily chore unless steps are taken to minimize water loss. Large pots retain more moisture than small pots because of the volume of soil, so we switched to bigger pots. Lining the inside of clay pots with clear plastic (just the sides, not the bottom) also helps reduce evaporation. Or, try coating the inside surfaces with a clear non-toxic sealant.

If I were starting again I'd consider purchasing cedar wood planters instead of clay or plastic. Wood planters compliment your wood deck wonderfully and blend into the outdoor decking area.

Of course, if I were starting at the very beginning and building my own deck or balcony, some of the planters would be built-in. They'd create the "walls" of an outdoor garden room and be designed to give privacy and to look like a natural extension of the indoor living space.

Depending on the construction of the deck or balcony, it might be wise to consult an architect or building engineer before installing a complete garden. For most rooftops, a few pots or planters would not be a problem, but large planters can weigh hundreds of pounds when saturated (the only reliable way to calculate weight). You must be absolutely certain a deck or balcony can bear the load.

No outdoor living space is completely comfortable in summer without protection from late afternoon sun. The building itself may provide that, if the balcony faces north or east. But direct sunshine from a south- or west-facing exposure can render a balcony useless for several hours each day.

Solve the problem by adding trellises to cast light shade or by building an open post-and-beam shelter, called a pergola. An experienced carpenter can recommend ways to brace these structures to make them sturdier.

Remember, vertical elements have to bear not only the weight of vines — and fruits, if you're growing vegetable such as cucumbers, as we did — they must also withstand wind. An upright surface covered with foliage takes a beating on a windy day.

Plant fast-growing annual vines, such as morning glory, cypress vine or hyacinth bean, in large planters at the base of each post. With good care and plenty of sun, they should cover the structure by mid to late summer.

If you prefer natural screening, erect a strong open frame that will support a collection of hanging baskets. Include plenty of cascading plant and arrange them at different heights to achieve maximum privacy.

Potted plants require more water and fertilizer — a lot more — than similar varieties growing in the ground. You'll be surprised at just how fast the recommended lightweight potting mixtures dry out.

To supplement those peat-based mixes, we added sterilized topsoil. Twenty percent by volume seems to be the ideal ratio. Real mineral soil helps the potting medium retain moisture and nutrients longer. As a result, plants stay healthier all season.

Water-absorbing polymer crystals are another standard ingredient, along with a generous measure of slow-release fertilizer. Slow-release plant foods don't provide vegetables or blooming annuals with complete nutrition, but they help. Supplement with soluble liquid fertilizer, such as fish emulsion, mixed at full strength. Apply as often as once a week when plants are blooming.

For a satisfying gardening experience, choose plants with exquisite fragrance, such as sweet peas, or those with blooms that open in the evening, like moonvine and evening primrose.

Plants with pink and red blossoms will attract hummingbirds to your balcony, and by season's end, sweetly scented butterfly bush (Buddleia davidii) will delight with its blossoms as well as with its brightly-clad winged visitors.