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Adding height to container gardens

Q: Can you recommend interesting plants that will add height to my containers?

Beth Dinsmore, Fort Wayne, IN

Beschorneria yuccoides and other tall, strap-leaved plants make effective focal points in container plantings. Photo/Illustration: Jennifer Blume

A: Kathryn Pufahl, designer of container gardens and president of Beds & Borders, Inc. , a wholesale grower of specialty plants in Laurel, New York, responds: Wonderful trailing plants abound for the container but upright plants are certainly more difficult to find and to select. Unfortunately, wholesale growers often ignore plants too large for large-scale production as well as tender plants that require excessive time to grow. There is, however, an increasing awareness among specialty growers and garden centers of the many fine selections for the center of your container.

You may choose a structural plant as the container’s focal point or select a trio of plants to create a soft, full-bodied appearance. For a focal point, try bold centerpieces like New Zealand flax (Phormium spp. and cvs.). Varieties such as the pink Phormium ‘Flamingo’ tend to grow slowly in a graceful clump, while the bronze Phormium tenax sits boldly upright. Substantial growth of the stiff broad blades will not occur in one growing season, so buy a mature plant for instant results. Phormium species and cultivars are easily overwintered in a dormant state at 38˚ to 40˚F and moved back into the garden in spring, where they will produce an even bigger display.

Other choices for height include Beschorneria yuccoides, an agave relative that works well as a centerpiece. Blue-green sword-shaped leaves arch gracefully from a basal rosette easily reaching 3 feet tall and as wide within a year. Xanthosoma sagittifolium ‘Chartreuse Giant’ with its arrow-shaped, vibrantly chartreuse, 15-inch-long leaves is a playful container centerpiece. Each leaf stands on a stem 2 or 3 feet above the pot in full sun or part shade. Contrast the foliage with blue-flowering plants or jump to the orange palette for a fiery combination. The burgundy leaves of Cordyline australis ‘Red Sensation’ branch off a central stem that will reach 3 to 4 feet in one season. Older leaves arch, while new stiff growth at the “head” of the plant gives a starburst, structural effect.

To achieve a soft yet tall effect in a container, arrange three tall plants in the center of a pot and fill in the edges with mounding or trailing plants. First select at least one foliage plant, such as a tall coleus (Solenostemon spp. and cvs.), for easy maintenance and long-lasting appeal. Then tightly situate sturdy, long-blooming selections adjacent to it for a showy display. Upright foliage plants good for this use include Plectranthus argentatus and Centaurea gymnocarpa, both wonderful gray accent pieces, or Persian shield (Strobilanthes dyerianus) with its bright-purple iridescent sheen. Good complementary flowering selections include tuberous dahlias such as Dahlia ‘Park Princess’ and D. ‘Purple Gem’, both cactus-flowering 2-foot varieties. Salvia guaranitica ‘Black and Blue’ grows 2 feet wide and tall, while gentian-blue blossoms emerge from black calyxes, or hoods, creating a striking contrast. Pentas cultivars, particularly the Galaxy series in white, pink, or rosy red, bloom the entire season, reaching 16 inches. Also try the variegated-leaf, pink-flowering Pelargonium ‘Mrs. Peters’. A plant with both interesting foliage and a pretty flower like this one is a desirable choice in the confined space of a container garden.