Oxalis makes a wonderful addition to container plantings, and the hardier varieties do well in sunny beds or partly-shaded borders. In addition to the green-leafed varieties that St. Pat might favor, Oxalis foliage can be shaded with silver, dappled in white, or darkened with deep purple tones. The plants also produce delicately pretty blooms, in white, pink or purple.
My purple-leafed Oxalis from the plant swap went into a pretty pot with some begonias last summer. I brought them in to decorate a sunny bathroom over the winter. When the begonias gave out, the purple shamrocks still looked great, so I got them some buddies at a local nursery - a pot of Oxalis ‘Iron Cross'. The purple centers of ‘Iron Cross' are a great complement to the larger dark purple leaves of O. triangularis. These two varieties turn up regularly even at stores like WalMart or Home Depot, but you may have to order other varieties by mail (don't forget to check Garden Watchdog for sources and reviews).
Regardless of foliage or flower color, Oxalis plants have some common characteristics. At night (or on cloudy days), the heart-shaped leaves fold together like sleeping butterflies. Underground, you'll find both roots and odd little tubers. In winter, or if they get too dry, your Oxalis may go dormant. As long as the little tuber is still intact, it will pop back up with fresh foliage. So don't be in too big a hurry to toss out that pot of "dead" Oxalis. Water the pot lightly and stick it in a warm place, or dig up the tubers and tuck them into another pot, and see what happens.
If you order tubers rather than purchasing potted plants, be prepared for a surprise. These look like no bulbs you have ever planted. EasyToGrowBulbs describes them as looking "like undernourished pine cones." (An exception to this is Oxalis triangularis, whose tubers closely resemble crocus bulbs.) How do you tell which way is up when you plant them? Fortunately, some of my new treasures had started sprouting in their packing bags, so I could tell that the tips of the pinecone-like scales should point up. If you're not sure which way to plant them, split the difference by placing them sideways.
The directions that came with my Oxalis said to plant the tubers just 1 to 2 inches deep. I decided to start them growing inside, on my light shelves. I sorted out the three largest tubers to start together in a bigger pot, to use as a house plant or to give away. The rest, I knew I wanted to tuck around in various places, so I started them individually. I filled 2 inch pots with my usual moist potting mix (soil-less mix with both peat moss and coir, plus polymer moisture crystals and a bit of time-release fertilizer). Using my fingers to plant let me be careful with the delicate sprouts on some tubers. I stuck a single tuber down into each cell, patted it into place, and watered it in.
Waiting for sprouts is always the hardest part for me. I only had to be patient for about a week before I saw new growth from these tubers, even on the ones that had no sign of a sprout when planted. From the very first leaves, the colors of my new prizes just shone. Often, a new perennial will make me wait two years or more for blooms. Not these! Some of them sent out budding flower stems even before putting up leaves! I'll let them continue to grow under the lights until the danger of frost is past, then I'll harden them off and plant them out.
Where to plant them? Oxalis is the perfect "filler" for the container trio of "thriller, filler, and spiller." Its soft clumps of foliage soften the edges of containers and fill in gaps between plants. I'm thinking about the other plants I've started or overwintered and envisioning all sorts of combinations: pink-flowered ‘Fanny' peeking out between double burgundy petunias accented with magenta ivy-leafed geraniums, deep purple ‘Mijke' echoing the color of purple fountain grass with the contrasting color and delicate texture of ‘Lemon Gem' marigolds, the dappled leaves of ‘Irish Mist' reflecting the silver of Dusty Miller and setting off the bright pink of ‘Zahara Starlight Rose' dwarf zinnias and the trailing blooms of ‘Pink Clouds' Achimenes.
Oxalis is also a great "shoes & socks" plant to use under leggy plants like oriental lilies and hardy hibiscus or to hide the yellowing lower leaves of garden phlox in summer. I was very excited to learn from PlantFiles that Oxalis triangularis and Oxalis ‘Iron Cross' should be hardy in my zone 6 garden. I'm starting several dozen plants to put along a brick walkway. They'll join Coral Bells, Japanese Ferns, and other purple foliaged plants that fill in the area beneath my butterfly Japanese maple, and they'll echo the color of the dark leaves on my hardy hibiscuses ‘Plum Crazy' and ‘Kopper King'.
Don't throw them out when summer ends! Although the less hardy varieties could be treated as annuals, I'd rather try to save them for next year. Dig the plants and tuck them into available nooks in your indoor containers, where you can enjoy their foliage all winter. Or carefully unearth those weird little tubers and store them alongside your dahlia tubers, caladium bulbs, and ornamental sweet potatoes.
With the new varieties now available, it's a great time to add some Oxalis to your borders and containers. I'm hoping these colorful "shamrocks" will bring luck to your garden and mine!
Photos by Jill M. Nicolaus.
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