Shamrock plants might seem dead, but could be dormant
Q: My shamrock plant’s leaves turned yellow and died back, and I have not seen any new growth over the last few weeks. Should I give up and buy a new one?
— José Rodriguez, Chicago
A: Potted shamrock plants are seasonal houseplants that are usually sold around St. Patrick’s Day, so you will have the opportunity to purchase a new one soon if needed.
But your plant may have simply gone dormant and need more time to rest. Many seasonal houseplants are discarded after flowering, though shamrocks can be long-lived houseplants with proper care.
Shamrocks are members of the wood sorrel family of the genus Oxalis. The leaves are clovershaped and come in a range of shades; some are bicolor and others are completely purple or solid green. Some people consider the plants to bring good luck because of the clover shape of the leaves.
The leaves of some species will fold up at night and open again when light returns. The plants can have small flowers during the fall, winter and spring when given proper care.
In general, shamrocks are easy to grow and will thrive when provided with bright light, such as in a west- or south-facing window. It will be best to protect the plants from extended periods of direct summer sun by adding a sheer curtain, moving the plants or shifting them to a different exposure. You can also grow them under artificial grow lights running 12 to 14 hours a day.
The more bright, indirect light you are able to provide for the plants, the
better color you will have in the leaves, along with improved flowering. The ideal room temperature for them is from 60 to 70 degrees Fahrenheit during the day, and 50 to 65 degrees at night, so most home environments should be fine. Try to keep them away from cold or hot drafts, if at all possible.
You can move your plants outside in late May after the danger of frost has passed. Gradually acclimate them to growing outside and keep them in dappled shade for the summer. Then acclimate them to growing inside in fall, before low temperatures approach 40 degrees.
Shamrocks prefer a uniform moisture in the growing medium and do not like to be overwatered. Thoroughly water the plants so that water runs out the bottom of the pot when the medium is dry, about 1 to 2 inches down in the pot. The growing medium surface will be noticeably dry at this point. Empty any excess water out of the saucers after watering.
They will perform best when humidity is low in the house. These plants have low nutrient requirements, so use a common fertilizer about once every four weeks between April and September. If you do not plan to grow your plant
for a long period of time, then you will likely not need to apply any fertilizer. It is best to fertilize when the growing medium is moist to avoid burning the roots with the fertilizer.
Groom the plants by cutting any spent flowers and yellow leaves on a regular basis to keep them looking their best.
Some shamrock species (likely your plant is one of them) need rest periods, also known as dormancy, which will start when all the leaves begin to turn yellow and then brown. Go ahead and let the leaves shrivel up and cut back on watering — keep plants dark, cool and relatively dry until new growth appears.
Gently remove all the leaves when completely dormant and stop watering for two to three months for green leaf varieties and approximately one month if it has purple leaves.
Once you see new foliage growing, move the plants back into the light and resume watering and fertilizing. You can repot the plants at this time, too.
For more plant advice, contact the Plant Information Service at the Chicago Botanic Garden at plantinfo@chicagobotanic.org. Tim Johnson is senior director of horticulture at the Chicago Botanic Garden.