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Oxalis

Purple or green Oxalis triangular is is commonly available around St. Patrick’s Day because of its resemblance to the shamrock or clover (oxalis is sometimes called “false shamrock”). Each stem bears three leaves, and house-plant parents love it that they drop down around the stem at night, like an umbrella closing, and then open each morning. The leaves “know” when to open by remembering the length of time spent in darkness. I once interrupted an oxalis while it was sleeping by exposing a few stems to a bright LED grow light for two hours. Those stems responded by opening to the light. A few hours later, when it was actually morning, the other stems opened, but the ones that got interrupted did not open until later in the morning, when the sun was higher in the sky.

Survival strategy

If you’re getting daytime highs of just 100 foot-candles, all the stems your oxalis initially came with will eventually wither away, until you’re left with just a pot of soil. Despite this total dieback of foliage, the bulbs are probably still alive. Keep the soil just barely moist, and occasionally aerate it so it’s not too compacted. In a few weeks, you should notice new stems emerging. The plant will never achieve the same fullness that it had in the nursery, but at this low light level, you should be happy with two or three stems per bulb.

Growth strategy

If you can get up to 600 foot-candles, the dieback of stems should be offset by new stem growth. Water whenever the soil is partially dry. If your oxalis is getting some direct sun, the soil may reach complete dryness within the same day, causing the stems to be droopy—water immediately and thoroughly! Dead stems can be easily removed by hand once they are completely dried. You can add a liquid fertilizer as directed whenever you see new stems growing.

Subjective life span

Oxalis bulbs can keep producing new stems after dying back, so don’t panic when you’re left with nothing but a pot of soil. Oxalis grows from a bulb, and it’s best to repot once the stems die back or when most of them are on their way to dying off. A regular potting mix of peat with some perlite will do.

Starting Oxalis from Bulbs

Day 1

You can buy oxalis bulbs and start them anytime. I bought ten on line and distributed them evenly on the soil surface.

Then I covered the bulbs with a thin (quarter-inch) layer of soil. Watered thoroughly and placed in a sunny window.

1 month

1 month since planting: A number of bulbs have put up one stem. Still more to come!

Here we see the early stages of a leaf stem (left) and a flower stalk (right, indicated by my finger). Remember to look closely at the soil level to catch a glimpse of these little ones.

2 months

The leaves have filled out nicely, and we’re now treated to some flowers!