Growing Purple Basil

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Last year, I fell in love with purple-leaved basils and could think of little else all summer. My ­season of obsession ended with a garden of nearly a dozen varieties, from the petite New Guinea with its arrow-shaped leaves to the voluptuous, ruffled foliage of the massive Italian Genovese Grande Violetto.

If you see green when you think basil, it’s time to take another look. The purple varieties shimmer with tender iridescence, and when the light is right and soil conditions have been just so, you can see highlights in the leaves that might seem purple or red or blue or maroon or violet or burgundy, or even green. These are the kinds of rare, joyful subtleties that startle the eye when viewing the impressionist canvases of Cézanne, but they can happen every day in the herb garden.

Whatever color you see in these basils, they have the same range of spicy anise scent and flavor, and the same uses, as green varieties: in fresh-picked salads, with fruits and cheeses, as garnishes, even in purple pesto if color-rich food is your pleasure. If you’ve a mind to be experimental, you can create a sinfully unusual treat by adding liquefied purple basil leaves to crème fraîche. Need I mention that purple basils excel in their traditional use for flavor and color in herb vinegar? Just ­because they aren’t green doesn’t mean that purple-leaved basils skimp on flavor; research conducted by Dr. James E. Simon at Purdue University in 1986 showed that the leaves of Dark Opal basil produced more ­fragrance- and ­flavor-producing essential oil than ­fourteen of the ­fifteen other basils tested.

Purple basils, like green ones, have the typical four-sided stems of the mint family, Lamiaceae (Labiatae), and carry their flowers in whorls of six blossoms each on spikes of varying length. Blooms begin opening at the base of the spike and work their way to the top. And purple basils have wild, flirtatious genes that give rise to many varietal changes. Botanists with a sense of humor like to lift an eyebrow and explain, with a twinkle in their eye, that basil varieties are “promiscuous” and cross among themselves and with other Ocimum species with abandon—a charming but frustrating trait. This lack of fidelity complicates our untangling of the lineage of the many offspring created by basil garden parties, but it also gives rise to an interesting collection of stories about how these basils have come to be, with and without the intervention of botanists, horticulturists, and growers like myself.

Ocimum basilicum ‘Purpurascens’

The granddaddy of purple-leaved garden basils may well be Ocimum basilicum ‘Purpurascens’, first identified in the 1830s by George Bentham, a British botanist. What is striking about this bushy, 2-foot-high basil is that as many as four pairs of leaves at the top of each stem are dark purple while the leaves lower on the stems shade to a pure, even light green. All the leaves are egg-shaped (about 11/4 inches wide and 2 inches long) and sparsely toothed along their margins. Whorls of small, light lavender to light purple blossoms are carried on 3-inch-long dark violet stalks, and the scalelike bracts at the flowers’ base and the calyces which encircle the corollas are both dark purple. The leaves, when brushed, release a pleasant anise scent.

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