Buttercup Oxalis and its Kin

Bermuda buttercup (Oxalis pes-caprae)

Bermuda buttercup (Oxalis pes-caprae)

Depending on your perspective, when you pass by a certain house on Rhodes Avenue in Studio City, you may see absolute neglect, the height of simplicity in a brilliant garden design, or God’s handiwork.
I am talking about a front yard where a single plant, Bermuda buttercup oxalis, occupies every square inch of ground. It really is a magnificent sight. Pure yellow flowers upon flawless green shamrock foliage cover an expanse of what was probably a lawn in bygone days. You cannot argue with the lush vista that meets your gaze. A powerful statement is being made, even if you are not quite sure who is making it or what it means.
Native to South Africa, buttercup oxalis (Oxalis pes-caprae) was imported to this country as an ornamental bedding plant, whereupon it quickly jumped (or perhaps crawled under) the garden fence and became, in the opinion of many, a weed. It even makes an appearance on “invasive plant” lists, which means it should never be intentionally planted since it could escape and wreak havoc in the ecosystem. Yet, one feature that makes its propagation problematic is its sterility.
Buttercup oxalis does not produce seeds, and I do not recall seeing it growing in the still undeveloped hills and canyons that surround us.
Buttercup oxalis propagates itself exclusively by vegetative means through replication of its bulb-like corms. A corm is a mass of tissue resembling a small bulb found at the base of stems or leaves of certain herbaceous perennials, including gladiolus, crocus, watsonia, crocosmia and 900 species of oxalis. Since it is not sold in nurseries, if you see buttercup oxalis in someone’s yard, it got there either with human assistance, whether transplanted or hitchhiked in with a load of topsoil; by water (the corms float); or through the activity of urban wildlife, whether an excavating squirrel or a bird.
Whatever your opinion of buttercup oxalis, it ceases to be an issue once warm weather comes, when it quickly dries up and disappears until the following year. Yet as long as it is there, you can at least add its leaves to your salad as a substitute for vinegar or lemon juice. All species of oxalis contain oxalic acid, a tart, salubrious compound that you taste when biting into spinach, Swiss chard or rhubarb. It is used to remedy ulcers and to reduce swelling and inflammations.
In large quantities, however, oxalic acid can be toxic, especially if you suffer from gout or a kidney condition.
Pink wood sorrel (Oxalis crassipes) is another mysterious, if equally delightful, garden enhancement.
Pink wood sorrel can pop up almost anywhere, at any time, and you barely have to water it. Its large mounding leaves form the biggest shamrocks you will ever see and its clusters of deep pink blooms are guaranteed to make you smile. Although it survives on little water, it will stay lush and flower for many months with regular irrigation, flourishing in either full or partial sun exposures but needing more water in garden hot spots.
Purple shamrock (Oxalis regnellii rubra) is a water thrifty oxalis that no shade garden should be without. Although it blooms this time of year in pale mauve, it shows off two-inch, burgundy-purple, triangular leaflets throughout the year. I really do not think it is possible to kill this plant, but it would prefer to have its soil kept on the dry side. Expect it to go dormant several times a year. Just when you are sure it’s dead, it comes to life again.
Volcanic sorrel (Oxalis vulcanicola ‘Molten lava’) is a wonderful ground cover with chartreuse foliage and red stems.
‘Zinfandel’ volcanic sorrel has burgundy leaves that contrast perfectly with bright yellow flowers.
A wonderful example of ‘Zinfandel’ is spilling out of a pot in front of Jasmine Blue Flower Shop, a Studio City florist on Ventura Boulevard just west of Ventura Canyon Avenue. As long as you are looking at ‘Zinfandel,’ you may as well notice the variegated Swedish ivy (Plectranthus coleoides) foaming up and out of another container nearby. This plant has lime green, coleus-type leaves scalloped in white. In yet another Jasmine Blue container, you will catch your breath at the sight of a compact Viburnum with deep green foliage and brilliant white, spherical flower clusters.
In Newhall the other day, I saw an outstanding Mediterranean tree mallow (Lavatera maritima).
This plant looks glorious for up to five years before it is ultimately tracked down and mercilessly attacked by insect pests – mealybugs, whiteflies and aphids – and soil fungus. But for those several years that it is healthy, nothing can match its pink-lavender splendor. At its peak, it is completely covered with hundreds of five-petaled flowers that will remind you of hibiscus, to which it is related.
In terms of longevity and cultural requirements, it reminds me of blue hibiscus (Alyogyne huegelii).
Both of these plants do best in full sun and with a minimum of water. Both plants are classic illustrations of the principle that dry climate plants demand ample sun from all four sides to bloom at maximum capacity. Both can also be pruned hard when flowering has finished to maintain more compact specimens.
Tip of the week
In the park/ranch site at the south end of Franklin Canyon, an extension of Coldwater Canyon at the end of Lake Drive near Beverly Hills, you will see a batch of orange red crocosmia plants, adjacent to a Hass avocado tree, in full bloom. Crocosmia ‘Lucifer,’ above, is one of the easiest plants to grow and spreads underground by corms in sun or partial shade. Over time, it forms massive clumps of tall, reed-like leaves and, in late winter, puts forth long, startling pokers of fiery flower spikes. Another collection of Crocosmia ‘Lucifer’ is visible on the south side of the Studio City river walk between Whitsett Avenue and Laurel Canyon Boulevard.

Pin It

Leave a Reply

Your email address will not be published. Required fields are marked *