Growing shamrocks indoors

Like many seasonal houseplants, shamrocks appear in floral shops, garden centers and other retailers for a short time.   While many seasonal plants are discarded after flowering, shamrocks can be long-lived houseplants with proper care.  

What is a shamrock and how is it different than a clover?
The common name of shamrock and clover are rather confusing as plants in several different genera are referred to by these names.  While almost any plant with 3 leaflet or trifoliate leaves can be called by a shamrock or clover, plants in the genera Trifolium and Oxalis are most frequently called shamrocks.  Plant species in the genus Trifolium include cover crops (such as common clover and red clover) and the common lawn weed, white clover. The shamrock that is commonly grown indoors is a plant species that belongs to the genus Oxalis.  While there are species of Oxalis that are native to Iowa (also commonly referred to as sorrel), the shamrocks used as houseplants are not winter-hardy outdoors in Iowa.  

Oxalis as shamrocks are grown for their large, green or purple foliage and 3-leaflet leaves.  They are not typically grown for their flowers – yet they frequently produce dainty white, lavender, pink, or even yellow flowers when grown in favorable locations and given good care.  Another interesting feature is that some species close their leaves and/or flowers at night only to reopen again the next morning.

Shamrocks
A shamrock with white flowers. Cindy Haynes

Growing shamrocks indoors
Shamrocks grow from modified stems or tubers with shallow root systems.  They prefer slightly moist, well-drained soils and often perform best when kept “pot bound”.  They prefer bright, indirect light in locations with cool night temperatures (around 60℉) and warm days (around 70℉).  Plants are often fertilized lightly with a dilute fertilizer solution once or twice a month during the growing season and after flowering.

Some Oxalis species have a dormancy or rest requirement. As plants enter dormancy, the leaves often turn yellow and die. This may be triggered by high temperature in late summer or shorter days/cooler nights of fall.  Dormancy typically lasts for 1-3 months and plants should be kept dark, cool, and relatively dry until new growth begins.  Once new growth emerges, plants can be water lightly and placed in bright, indirect light for full leaf development.  When plants are receiving plenty of light, they often produce blooms as well.

There are several species and cultivars of shamrocks that are sold around St. Patrick’s Day.  There is even a Lucky Shamrock plant (type of Oxalis) with mostly 4-leaflet leaves instead of 3-leaflet leaves.  Good luck!

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