After spending enough time with their hands in the dirt, most gardeners come to the same conclusion: it's all about foliage. Among the aristocrats of plants grown primarily for foliage is the giant honey flower, Melianthus major. The genus Melianthus (which literally means honey flower) is among only three genera within the Melianthaceae, a small family native to Africa and India. Melianthus major is a common denizen of the southwestern Cape, where it grows in parched, disturbed sites, often on roadside verges. Somewhat raw in appearance in nature, it becomes a swan in the garden with a bit of coddling. The pinnately compound leaves, to 15 inches in length, are composed of jagged-edged leaflets that are an arresting blue-gray color. They are carried on subshrubby stems to five feet or slightly more in height. In early spring, tubular deep burgundy flowers, heavily scented of honey, are borne above the foliage. Because the flowers are produced on second-year wood, flowering will occur only if the plant is not cut to the ground by winter (or pruners). In the Pacific Northwest, we generally lose the stems to winter cold before flowering occurs. With that said, the floral display we witnessed after one particularly mild winter left us unimpressed. We therefore opt to cut the plants back hard before growth resumes in spring, regardless of how severe the preceding winter has been.
Melianthus major will survive in the open ground in USDA Zones 7 to 12 if planted in well-draining soils in open, sunny sites. Siting it in a favorable microclimate, such as along a protected south-facing wall, can increase its hardiness significantly. We've found that placing the crown of the plant three to four inches deeper at planting time increases its chances of survival.
Fortunately for gardeners in colder climates, M. major makes a particularly good containerized specimen, being both drought tolerant when fully established and also adaptable to the travails of being pot-bound. It can be stored in a cold greeenhouse or sun porch during the winter, and the stems should be cut back hard, to three inches, just as growth resumes in spring.
Until recently, most melianthus offered for sale in North America were produced by seed, which germinates readily if sown fresh (though the seed's high oil content makes it tasty to foraging mice, thus requiring protection for seed trays). The young plants establish quickly, and it's possible to have a nearly mature specimen in a single season. Lateral cuttings can be taken in late summer and treated like hardwood cuttings.
Because seed-grown melianthus is so variable, it is fortunate that two clonal selections are now available. Melianthus major ‘Purple Haze‘ was named by plantsman Roger Raiche, who noticed it while visiting the Dry Garden, a nursery in Berkeley, California. It is an outstanding selection with a greater suffusion of purple throughout the stems and the steely blue leaves. It also boasts a finer textural quality than most seedlings. The late and great Seattle gardener Steve Antonow selected and distributed a particularly good seedling with a bolder texture than ‘Purple Haze’ and a dazzling blue-aluminum foliar patina. I named it ‘Antonow's Blue' in Steve's memory.
Whether in containers or in the open ground, M. major lends itself to countless exquisite combinations. In a container, consider underplanting it with Sedum sieboldii, whose rounded, succulent, gray-and-rose-tinted foliage carries on an eloquent dialogue with its taller companion. In my new seaside garden, I have used melianthus in large sweeps as a tall groundcover in full sun. It grows next to the spectacularly blue Eucalyptus glaucescens, and is knitted together by roving bands of Mexican feather grass, Stipa tenuissima. But these are only points of departure. I would be pleased to hear how other gardeners throughout the country have used this superb shrub.
TYPE OF PLANT: evergreen shrub
RANGE: southwestern Cape, South Africa
HARDINESS: USDA Zones 7–11; Sunset Zones 8, 9, 12–24
HEIGHT/SPREAD: 5–10 ft./6–8 ft.
FORM: semierect to sprawling
GROWTH RATE: rapid
LEAVES: pinnately compound, to 15 in, long, leaflets ovate-oblong, coarsely serrate, glaucous
FLOWERS: small, borne in erect racemes, dark reddish brown, highly fragrant
CULTIVARS: ‘Purple Haze‘; stems and leaves suffused with purple, finer-textured than most; ‘Antonow's Blue’; bold-textured, leaves with silvery blue patina
SITE REQUIREMENTS: full sun to light shade in moisture-retentive, well-drained soil
PROPAGATION: by seed or lateral cuttings taken in late summer