Cupheas at Strybing Arboretum

The annual Cuphea lanceolata makes a handsome edging along a path at Strybing Arboretum and Botanical Gardens. Author's photographs

The annual Cuphea lanceolata makes a handsome edging along a path at Strybing Arboretum and Botanical Gardens. Author’s photographs

Cuphea (From the Greek kyphos, curved, alluding to the curved fruit capsule.)

Hyam and Pankhurst, Plants and Their Names

Cuphea is a genus of about 260 species in the loosestrife family (Lythraceae), the same family as crape myrtle (Lagerstroemia). The distribution of this genus extends from central and eastern North America to Brazil and Northern Argentina. Growth forms range from upright annuals or spreading herbaceous perennials to woody shrubs in the range of six to ten feet. Many are exceedingly floriferous, and perennial species may flower almost the year round in coastal California gardens.

The flowers of Cuphea are either borne singly, clustered in leaf axils, or on terminal racemes. Each consists of a floral tube (referred to as a calyx tube in many references) created by the union of calyx and corolla throughout all or part of their lengths. This structure is often spurred below and may bear either six or two apparent petals emerging from the floral tube by narrow bases. Sometimes there are no visible petals. When there are six petals, two on the top of the tube—a dorsal pair—tend to be enlarged and showy. It is this dorsal pair that remain in those species with only two prominent petals; these species are often referred to as having “bat-faced” flowers. If one looks closely, particularly with a hand lens, the full complement of petals and sepals may sometimes be seen as tiny appendages at the tip of the floral tube. Flowers are visited predominantly by bees in some species, and by hummingbirds in others. Syrphid or hover flies have a voracious appetite for the pollen. Seeds are produced in a capsule that splits open along one side. Mature capsules often protrude from floral tubes that are still showing good color. When the capsules open, a quick look may give the impression that these saucy little flowers are sticking out their tongues at the gardener. Self-sowing is common.

Even a species long established in horticulture, such as Cuphea ignea, has untapped variability waiting in the wild, as seen in this large-leafed form collected by Don Mahoney and grown at Strybing Arboretum and Botanical Gardens

Even a species long established in horticulture, such as Cuphea ignea, has untapped variability waiting in the wild, as seen in this large-leafed form collected by Don Mahoney and grown at Strybing Arboretum and Botanical Gardens

Mexico has been a particularly rich source for the species in cultivation. The two most widely known are cigar flower or firecracker plant (Cuphea ignea) from Mexico and Jamaica and false heather (C. hyssopifolia) from Mexico and Guatemala. These once were about the only species readily available in West Coast nurseries. In the last few years, the selection has been increased with the addition of some reliable garden performers. Several have entered California horticulture through the work of botanist Dennis Breedlove, formerly with the California Academy of Sciences in San Francisco’s Golden Gate Park. Nearby in the park, Strybing Arboretum and Botanical Gardens has been a repository for Dr Breedlove’s horticultural collections since he began his work on the flora of Chiapas, Mexico’s southern-most state.

With only a few wild cupheas in cultivation, there are surely more good horticultural subjects in the genus awaiting introduction. As many of us growing several species together in the confines of our gardens have discovered, Cuphea tends to be promiscuous; herein may lie a source of confusion, but also exciting potential for future garden-worthy selections.

As you will see in the following descriptions, almost the full range of habit to be found in this rewarding genus is represented among the cupheas growing at Strybing Arboretum. Horticultural characteristics shared by most include: easy propagation and rapid development from seed or cuttings, a requirement for regular watering, an ability to thrive in bright shade to full sun, adaptability to a variety of soil types, a low requirement for fertilization, frost tenderness to varying degrees, a freely branching habit, copious flower production over a long period, and vulnerability to few pests or diseases when grown outdoors. White fly and aphid infestation can cause problems in a greenhouse situation.

Cuphea aequipetala can make an attractive groundcover, here seen with Tagetes lucida

Cuphea aequipetala can make an attractive groundcover, here seen with Tagetes lucida

A Sampling of Cupheas

Cuphea aequipetala Cav. has been in cultivation for some time, but plants available in California today probably derive from Breedlove’s collections in Chiapas; it has been grown at Strybing Arboretum since at least 1991 and at UC Botanical Garden (UCBG) in Berkeley since 1981. The natural range for this species extends from southern Mexico to Guatemala. The common name in Veracruz is apancholoa. In Chiapas, plants are found at elevations of 4,000 to more than 9,000 feet in pine/oak, liquidambar, and evergreen cloud forests, as well as on disturbed slopes and pastures. It reportedly has been used medicinally for painful urination. Young plants in cultivation grow initially as six- to eight-inch tall, spreading mats that can reach two feet across before much vertical growth occurs. As flowering commences, taller shoots are produced that may reach three feet in light shade, but are usually two feet or less. The form in cultivation at Strybing has lanceolate or ovate leaves from one-quarter to one and a quarter inches in length and one-half inch in width. The flowers, popular with bumblebees, are borne on leafy shoots. They are small but profuse, have short pedicels and six petals; two are reflexed and dark purple, four are spreading and rosy purple. The floral tube is purple and green. Plants were severely damaged at 16° F during the freeze of 1990, but re-grew from mulched crowns and from seed. This species was used successfully at UCBG as an attractive ground cover on a steep and unstable slope. Although prostrate stems root sparingly, the dense shrubby mats and seedlings aid in slope stabilization. Among seedlings at UCBG, a small percentage are extreme dwarfs. Taller, more upright forms with slightly larger flowers have arisen in the Upland Mexico plantings at Strybing; these may represent variation within the species or, as suggested by horticulturist Don Mahoney, hybridization with the annual C. lanceolata cultivated in the New World Cloud Forest plantings.

Cuphea subuligera, orange form

Cuphea subuligera, orange form

A Breedlove collection without previous cultivation history, Cuphea subuligera Koehne has been grown at Strybing since 1984 and at UCBG since 1976. It is found in the states of Puebla and Chiapas, Mexico, growing at elevations from a little under 5,000 to almost 9,000 feet in evergreen cloud forest and regenerating montane rain forest. It is a dense, upright, shrubby plant, to about three feet tall and equally wide in cultivation, although in nature it may reach six feet in height. The leaves are borne on short petioles and may be from two to three and a half inches long and one and a half to two inches at their widest, tapering to a sharp point. The glabrous foliage is shiny and attractive. The flowers, popular with hummingbirds and produced almost year round, are borne on distinct racemes with short pedicels. Individual flowers are tubular, from three-fourths to one and one-quarter inches in length; the tube flares at the mouth, lacks apparent petals, and bears glandular hairs. Flower color in the wild varies from pink through lavender, purple, magenta, and orange. Two color forms were originally grown at both Strybing and UCBG, one pale lavender pink, the other fiery orange red. These have since hybridized extensively to produce many intermediate colors. The orange red flower form was grown for many years as C. caeciliae Koehne. Local medicinal uses attributed to it include treatments for fever, wounds, snakebite, and eye problems. It differs from the pink form in holding racemes higher above the foliage and bearing larger flowers. Both forms were severely damaged at 16° F during the freeze of 1990 and grew back weakly from seed and mulched crowns. In Marjory Harris’s San Francisco garden, the orange red form has apparently hybridized with cigar flower (C. ignea), yielding plants vegetatively like C. subuligera, but with flowers that bear white markings at the tip.

Cuphea oreophila is one of the more woody, upright species and can be used as a hedge

Cuphea oreophila is one of the more woody, upright species and can be used as a hedge

Cuphea oreophila Brandeg. ex Bacig., a Breedlove collection without previous cultivation history, has been grown at Strybing since 1987. It is found in the state of Chiapas near its border with Oaxaca, at elevations from 4,500 to about 5,500 feet, in montane rain forest as well as pine-oak-liquidambar forests. It is a woody, well-branched, upright shrub reaching ten feet in the wild, but seldom more than three to four feet in cultivation. The strongly veined leaves are lime green, two to three inches long, one to one and a half inches wide at their widest, and covered with glandular hairs. The flowers are borne in the leaf axils. The floral tubes are about one and a half inches long and bear two ruffled, half-inch-long, dorsal petals held erect. Both the floral tube and the petals are an intense, glowing orange red. This species is a little less cold hardy than the others and can be susceptible to mite damage without regular overhead watering, but the flower color is extraordinary. It has been used with success as a hedge plant at Strybing and does not spread by seed.

Another Breedlove collection without significant cultivation history, Cuphea nudicostata Hemsl. has been grown at Strybing since 1987 and at UCBG since 1990. It was originally identified as C. nelsoni Rose. and grown under that name until recently. A single herbarium sheet exists at the California Academy of Sciences Herbarium, labeled C. aff. nelsonii [sic] and listing the following information: collected in Chiapas at 7,600 feet in open pine forest with oaks and Clethra, reaching about three feet in height with red flowers. In cultivation, this species is a low sub-shrub with wiry stems, spreading widely but seldom over two feet in height. The pale leaves are two to four inches long, about two inches at their widest, and covered with glandular hairs. Flowers are borne sparingly in the leaf axils. They are about one inch long with a pale yellowish green floral tube that bears two half-inch, bright orange red, dorsal petals held erect. Bright light encourages flowering, but this is not a particularly floriferous plant. Cold hardiness is similar to that of C. oreophila. It was used with some success as a shade ground cover at UCBG and does not spread by seed.

Cuphea micropetala, one of the showiest, is more cold hardy than most species

Cuphea micropetala, one of the showiest, is more cold hardy than most species

Cuphea micropetala H. B. & K., from the states of Colima to Morelos and Oaxaca, Mexico, has a long cultivation history, and plants currently grown at Strybing and UCBG were not wild collected. It is an upright shrub to three feet with relatively heavy, hairy stems that do not branch as densely as some of the other species. The handsome, rough-textured leaves are oblong to narrowly lanceolate from two to six inches long and half as wide, tapered at both ends. The flowers are borne on terminal racemes. The floral tube is from one and one-fourth to one and one-half inches long; petals are not apparent. Buds and the youngest flowers are yellow, each taking on an orange red cast in its lower half while maturing, and eventually becoming entirely orange red, so that the racemes are shaded from yellow to orange red along their length. The stamens often stick out beyond the calyx tube. This species is significantly more cold hardy than the other species described here, tending to drop its leaves in cold weather but re-growing both from existing stems and from the slowly spreading crown in late spring. It was little damaged in the freeze of 1990, and it does not spread by seed.

A beautiful annual species from Mexico listed in floras for the states of Chiapas and Veracruz, Cuphea lanceolata Aiton was collected by Dennis Breedlove and Don Mahoney in Oaxaca State. The species had been in cultivation for some time, but plants currently available in California probably originate from their collection now grown at Strybing. Although described in Hortus III as growing up to four feet tall with leaves up to three inches long, the plants at Strybing seldom exceed two and a half feet in height and about one and a half feet in width, with lanceolate leaves up to two inches long. All plant parts are sticky glandular except for the petals. Flowers are borne in leaf axils and produced in abundance from late spring through fall. The floral tube is up to one inch long and bears six petals, with the dorsal pair dark purple and measuring half an inch long and wide—about twice the size of the paler ventral petals. Plants escape frost as seed and return reliably in open sites. They have made an attractive edging to several beds in Strybing’s New World Cloud Forest section.