Sun Shamrocks and Alleluia Flowers

The overlapping flower petals spiral to a point when the flower closes at night and on cloudy days, but they unfurl quickly on bright days, even in shade.

Rob Proctor, Naturalizing Bulbs

It wasn’t much of a lawn, that ragged piece of turf that functioned as such in my first California garden some thirty years ago; it was well populated by a lot of plants that were not grasses. Flowering with pink or, less often, white upturned bells, one plant persisted no matter how many times it was shorn to the ground by the mower. Too attractive to be merely a weed, I began to dig up the roots and use the plants as edgings, Southern California’s answer to the London pride and cottage pinks of my mother’s English garden.

Evergreen and with ten months of bloom, it continues to make a splashy edging plant. The flowers are small but come in such profusion that they more than earn the space given to them. Though rarely more than nine inches tall, if it does get overblown, shearing back soon restores its tidiness. Eventually, at The Arboretum of Los Angeles County in Arcadia, I found a clump of it labeled Oxalis crassipes. The name now seems to have gone from the plant manuals, replaced by O. rubra. Later I found that, although South American in origin (Brazil? Chile? I’ve seen it listed as native to both), it was known to English cottagers. Planted by a doorstep, it was prized both for its beauty and as a weather forecaster, since this sun‑lover closes up its petals during rain, on overcast days, and at sundown.

There are some 800 species of oxalis in the world, but only a small portion of them appear in our gardens. A few rogues and rampers have given the genus a bad name. Oxalis rubra is not—for me, at least—invasive. A mounding rhizomatous plant, it will, if left undisturbed, put on a great bulk of underground growth, resembling nothing so much as a disembodied brain from some monster movie.

Surely something so easily grown must have acquired a common name somewhere along the line. Other species of Oxalis are known in the vernacular: wood sorrel for O. oregana, firefern for O. hedysoirides ‘Rubra’, Mexican pink buttercup for O. lasiandra. But O. rubra seems to be unsullied by the vernacular.

Oxalis rubra. Photographs courtesy Helen Crocker Russell Library of Horticulture, except as noted

Oxalis rubra. Photographs courtesy Helen Crocker Russell Library of Horticulture, except as noted

A Common Garden Flower

At the end of Elizabeth Lawrence’s Gardening for Love, so admirably edited from her posthumous papers by Allen Lacy, there are eleven pages of common names, but no oxalis. Miss Lawrence did have Oxalis rubra, though, in her North Carolina garden, “one of the common garden flowers hereabouts,” unsure of its identity until she got a matching plant from California. Her description of its coloring, “rosalane purple with a dark throat made up of fine lines of red-violet” is unbeatable. I had always thought of it as dark pink.

Oxalis rubra is a plant for homemade gardens. I never see it where everything is carefully monitored and manicured, and landscape designers do not seem attracted to it. It does turn up in garden centers around St Patrick’s Day, one of various plants sold as “Irish shamrock,” bringing no discredit on that Celtic saint. I have heard it referred to as sun shamrock or alleluia flower (from its habit of folding up as the sun sets), but if these are common names, they are even less familiar than the botanical ones. Louise Beebe Wilder listed cuckoo bread alleluia flower as a common name for O. acetosella, but that species does not seem widespread either.

Oxalis adenophylla

Oxalis adenophylla

Of oxalis, I’m neither avid collector nor connoisseur, merely an admiring bystander who plants what comes his way. The bulbous ones have always done better than the fleshy rooted ones in the sandy alkalinity of my soil. Oxalis triangularis is a striking stand-out with burgundy colored leaves and pink flowers; it is the least invasive of any oxalis I’ve ever grown. Oxalis adenophylla, is a lovely Andean species with grayish clover-like leaves and pink flowers. Oxalis deppei (O. tetrophylla) is another distinctive plant with its four-lobed leaves, each with a purplish center (there are some striking forms of this in the cultivar known as ‘Iron Cross’). Oxalis lobata, from Chile, is a small yellow-flowering bulblet, around four inches tall, best grown in a container since it is easily swamped by the competition. Oxalis enneaphylla originates in the Falkland Islands and the Straits of Magellan, but was taken back to England in the 1920s by the fine nurseryman, Clarence Elliott. I’ve failed with this one. It likes cool growing conditions—not surprising considering where it comes from—and all I can offer is warmth. Botanical illustrations show “wide silky flowers spread over the grey folded leaves,” as Graham Stuart Thomas once noted. The foliage, with its multi‑fingered leaves, more closely resembles Geranium maderense than most oxalis.

Oxalis pes-caprae. Photograph by RGT

Oxalis pes-caprae. Photograph by RGT

The Invaders

Then there are the invaders. Creeping wood sorrel (Oxalis corniculata) and its red-leaved form are good-looking enough with a froth of miniature leaves and tiny yellow star-like flowers, but are garden wanderers that, given an inch, will take over a yard. The species, though, that has forever blighted the name of the genus is Bermuda buttercup (O. pes-caprae). When I first saw it massed in cadmium-yellow across waste sites in Los Angeles, it was an unforgettable floral sight, clothing broken ground with that same healing touch the rosebay willowherb (Epilobium angustifolium) brought to blitzed sites in Britain in the 1940s. It’s easy to understand why Kate Sessions, nurserywoman and beautifier of San Diego, urged its greater use on parkstrips and roadways of the city in the teens of last century.

When I came to my present garden, Bermuda buttercup was waiting for me, supremely confident that its mission was to populate the earth or, at least, all the temperate climates thereof. Growing from a deep-rooted scaly bulb, it can develop a probing taproot; long, fleshy, and translucent, its demon finger scrabbles through the earth and is impossible to dislodge. Elizabeth Lawrence tells us in The Little Bulbs that she wanted it but found it hard to come by. She got it in the end, planting bulbs in early December that flowered in early May. Her climate in Charlotte seems cold enough to have kept a check on it (she wrote that, for her, O. rubra died down in cold weather).

How did Bermuda get blamed for such a vicious weed? The only answer I could find came, unexpectedly, in the handy pocket‑sized paperback Flowers of Greece and the Aegean by Anthony Huxley and William Taylor. There, it is treated not as a South African transplant, but as an inescapable element in the Greek floral landscape, growing on agricultural land, in vineyards, and olive groves—too conspicuous to be ignored.

Huxley and Taylor say it was taken from Bermuda to Malta and from there, spread by bulbils throughout the Mediterranean region. The book had photographs of both the single and the double form (‘Flore Pleno’). The double form, when found, is likely to be predominant in that area.

Their explanation is not, perhaps, a satisfactory one. How did it make a landfall in Bermuda? And from that speck in the Atlantic to an island in the Mediterranean? Did the British Navy have anything to do with its circumnavigational progress, colonizing as it went? If these botanical mysteries have answers, I’d be glad to hear them. Huxley and Taylor do state that “Ironically it is sterile and doesn’t set seed. Neither cultural practices nor weedkillers can destroy it.”

The leaves of oxalis are said to be edible and suitable for salads, with the proviso that too many of them, and thus too much oxalic acid, could prove poisonous—a somewhat strange way of living dangerously. Oxalis tuberosa has, however, for centuries been grown as a food on the cultivated terraces of Peru. In his Cornucopia: A Source Book of Edible Plants, Stephen Facciola writes: “When dried in the sun the edible tubers become wrinkled, dry, floury and sweet, and the calcium oxalate content is reduced. They are then eaten raw, boiled in soups or stews, or candied like sweet potatoes. Further drying produces cavi, which is eaten with honey or sugar cane as a dessert, and chuna de oca, a dessicated product that gives a distinctive flavor to stews.”