The care and feeding of purple-leaf shamrocks

A double-duty cutie, the purple shamrock is good for both home and garden.

Purple shamrock. Photo by Rebecca Finneran, MSU Extension

Purple shamrock. Photo by Rebecca Finneran, MSU Extension

The purple-leaf shamrock, Oxalis triangularis, is a low-growing foliage plant for the garden that also makes for an attractive indoor plant with rich, vibrant, purple leaves. Smart gardeners have gravitated to this beautiful foliage plant to add color indoors and outdoors for several decades.

This Brazilian native came to the United States in the 1980s and its popularity continues to grow. Indoors, it can fill a pot with rich, purple leaves and add a dash of color to the often green indoor plant world. It is actually multiple small plants that grow as a group from bulbs. It has minimal needs, but one thing it cannot tolerate is overly wet soils. It is critical that the plant is in a container with a drain hole and is not overwatered. If this shamrock is exposed to temperatures above 80 degrees, it can wilt and go dormant. Michigan State University Extension horticulture educators and hotlines receive calls about the mysterious shutdown of a previously vigorous shamrock.

Outside, purple shamrocks are put into areas that are somewhat shaded. Because they are not much taller than 6 inches, they need to be in the front of the bed to be seen, or they could be in a container that needs season-long color. When the weather is warm and there is adequate moisture, the shamrock blooms with small, pale pink, bell-like flowers. By fall, the happy shamrocks will have multiplied themselves. Now, it’s time for the big decision. They can be dug and put into a pot and play the role of an indoor plant during the winter, or it is possible to store them like other summer bulbs in a dormant state and reactivate them in the spring.

If the shamrock is going indoors as a growing plant, dig the plant in mid-September before any frosts. This keeps the foliage looking good. Place into a container with a drain hole and water well to settle the soil. When the shamrock is indoors, place in a sunny window. The plant can handle more sunlight indoors because the windows filter out some of the light, and the days are growing shorter so there is less light intensity. The windows that usually have the most sunlight are, in order, south, west, east and avoid north because there may be none at all.

If the bulbs are going to be stored for the winter, dig chunks of roots and bulbs and gently remove as much soil as possible without having the chunks of tightly packed bulbs break apart. Place into a cardboard box and bring into the house until the foliage dies down and dries up. You can find small bulbs, called pips, or you may find short, fat, carrot-shaped tubers with bigger plants that had a great growing season. Once the foliage has dried up, cut off close to the soil surface. This might take a week or so. Store the clumps of bulbs in a container like a cardboard box or paper bag and nestle them into a bed of dry sphagnum peat moss, Canadian peat, wood shavings or vermiculite. The peat has the extra advantage of being acidic and preventing any rots if they should start. Root clumps should have a buffer of packing material under around and over them. This will slow drying of the bulbs. Place the container somewhere that is going to be dark and the temperature should be between 40 and 50 degrees. Cool and dark conditions keep them dormant. Freezing is fatal.

In the spring when all danger of frost has passed, which is usually from the middle to late May, plant the stored clumps about 1 inch beneath the soil and water well. It will take four to six weeks for the new growth to begin. Your indoor shamrock can be freed from its pot to run wild again.

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