Plants for sunroom gardening - includes list of nursery sources - Cover Story

Flower & Garden Magazine, Feb-March, 1994 by Anne Swithinbank

To Sit Under a Canopy of Flowering Climbers in a sunroom lush with exotic plants is to bask in the delightful environment these rooms offer. Gardeners who fulfill the dream of adding a sunroom or conservatory to their houses are indeed fortunate.

In the protected, bright space of a sunroom, growing conditions can be controlled and plants are safe from the excesses of outside weather. Gardeners may use this advantage to increase their plant collections, because suddenly a whole range of plants that need more light, greater humidity and perhaps less severe winter temperatures to flourish can be grown and brought to flowering.

Successful sunroom gardening depends as much on careful choice of plants as on the gardener's skill in caring for them. The minimum winter nighttime temperature available in the sunroom will greatly influence plant selection. For instance, merely excluding frost by keeping temperatures at or above 38 degrees will keep many plants happy and thriving; others will remain alive but dormant at this temperature, while those with truly tropical preference will languish and die. Many plants from the Mediterranean, South African and Australian climates, such as Prostanthera (the Australian mintbush), acacia, cyclamen, Erica canaliculata and other South African heaths, need cool winter temperatures. If coddled in a sunroom that's too warm and humid, they will keel over, making a disaster of the match between growing conditions and plant selection.

Once the temperature range has been determined, select plants suitable for the growing conditions while thinking of the sunroom as a small garden. Choose larger specimen plants first, then climbers to clothe the walls and supports, trailing plants to fill hanging baskets and wall planters, then finally the smaller foliage and flowering plants that will bind the rest together.

For economic reasons, it may be impossible to provide heat in a sunroom. However, one that is positioned to receive winter sun will still be suitable for a number of plant choices and provide the gardener a pleasant place to sit. In northern states, camellias can be brought to bloom in cool conservatories, producing flowers less likely to be turned brown by frost. Bay trees trained as standards or pyramids are showy and aromatic. The New Zealand flax (Phormium tenax) has interesting, sword-shaped leaves that, depending on the variety, may be brilliantly striped.

Specimen plants are great stylesetters. Traditionally designed sunrooms reminiscent of great historic orangeries could house a collection of citrus. Although oranges, lemons, limes and grapefruit can tolerate temperatures that dip almost to freezing, they prefer temperate conservatories where minimum night temperatures never fall below 40 degrees. Glossy aromatic foliage, scented blossoms and edible fruit will repay the effort of correct feeding, controlling excessive summer temperatures and keeping pests at bay.

In a cool house, the soft green leaves; of indoor linden, Sparmannia africana, contrast well with darker-leafed plants. Indoor lindens produce their white flowers early in the year. Tickle the bush of yellow-brown stamens and they open out as if by magic.

An Oriental atmosphere can be created by using bamboo and sacred bamboo (Nandina domestica). Although these will grow in wide temperature ranges, including warm sunrooms, they are happier and perform better in cooler settings. A warm, sun-baked look may be staged by mixing bougainvillea, oleander, hibiscus and angel's trumpet (Brugmansia). A modern style would benefit from fewer, more dramatic plants, while a cottage style would take in those like pittosporum and acacias with smaller, more delicate leaves.

Because of the heat needed to raise winter temperatures in cold climates, tropical conservatories, which must maintain temperatures above 60 degrees at night, are perhaps not so common. Yet, wherever they are feasible to maintain, they have a style all their own. Mimicking the profuse growth of a tropical rain forest, they are great fun to create. Lush fiddle-leaf figs, giant Medinilla magnifica (the rose grape from the Philippines) with its enormous leaves and hanging bunches of pink flowers, philodendrons and perfumed frangipani (Plumeria) are just some candidates. False "trees" of cork bark or dead tree branches can be used as homes for epiphytic bromeliads, ferns and orchids. Dwarf bananas lend a touch of the exotic. The extra humidity that must accompany the heat means the furnishings must be chosen with care.

Some of the most spectacular sunroom flowers are climbers. In an unheated sunroom, try Abutilon megapotamicum, which must be tied to a wall for support. Its bell-shaped red and yellow flowers appear during summer. English ivy makes welcome swags of foliage, and some varieties tolerate considerable amounts of cold. Deciduous climbers, such as grapevines, are particularly useful as their leaves drop to let light through in winter.

Suitable climbers for sunrooms with nighttime temperatures above 40 degrees include blue or white Plumbago auriculata, pinkish-orange Campsis x tagliabuana |Madame Galen' and passion flowers such as Passiflora |Incense' and P. incarnata. The purple pealike blooms of vine lilac (Hardenbergia violacea) are always welcome sight in the depths of winter. For a large space, scented Buddleia asiatica produces graceful wands of tiny white flowers in winter.