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Shamrocks and St. Patrick’s Day

If you visit your favorite garden center in late February or early March, you’ll likely find shamrock plants to coincide with the St. Patrick’s Day holiday. The myths and folklore surrounding St. Patrick are quite fascinating, although perhaps not factual.

As the legend goes, St. Patrick used the plant to explain the concept of the Holy Trinity, but the term shamrock wasn’t documented until well after St. Patrick’s time, first appearing in plays and poetry in the 1500s. It wasn’t until 1596 that the term was connected to an actual plant, when an English herbalist wrote that the common meadow trefoil was “called in Irish Shamrockes.”

While we may never know the shamrock’s true identity, it was probably a clover (genus Trifolium) rather than a wood sorrel marketed as a shamrock (genus Oxalis). Plants from both genera may be trifoliate, but Trifolium leaflets are oval while Oxalis leaflets are heart-shaped. Both genera may be considered weeds when found growing in turfgrass. If this is a concern, HGIC 2319, Oxalis Control and HGIC 2324, White Clover provide control options. Other than these similarities, wood sorrels and clovers don’t have much in common, which isn’t surprising considering they are from two different plant families.

The striking purple foliage of Oxalis triangularis gives it the common name “purple shamrock”. Terasa Lott, ©2021, Clemson Extension

The striking purple foliage of Oxalis triangularis gives it the common name “purple shamrock”.Terasa Lott, ©2021, Clemson Extension

While shamrocks are considered foliage plants, they do produce dainty, 5-petaled flowers. Terasa Lott, ©2021, Clemson Extension

While shamrocks are considered foliage plants, they do produce dainty, 5-petaled flowers.
Terasa Lott, ©2021, Clemson Extension

Many Oxalis species move their leaves in response to light intensity (nyctinastic). You’ll notice the leaves are folded in this picture which was taken in the house at night. Terasa Lott, ©2021, Clemson Extension

Many Oxalis species move their leaves in response to light intensity (nyctinastic). You’ll notice the leaves are folded in this picture which was taken in the house at night.
Terasa Lott, ©2021, Clemson Extension

The good news is that you don’t need the luck of the Irish to grow Oxalis as houseplants. Here are a few tips for success.

Light: Bright, indirect light.

Temperature: Normal indoor temperatures, although cooler nights, will prolong flowering.

Water: Slightly moist but well-drained. Oxalis also prefer being a bit crowded in a pot, aka “potbound.”

Fertilizer: Apply a houseplant fertilizer 1-2 times per month while actively growing or flowering.

If your plant starts to look sick, do not despair. Some Oxalis species require a rest or dormancy period. During this time, plants should be kept cool, dark, and somewhat dry until new growth begins. At that time, the plant can be watered and returned to bright, indirect light.

Reference:

  1. Lovejoy, Bess. (2015). No One Really Knows What a Shamrock Really Is. Smithsonianmag.com

If this document didn’t answer your questions, please contact HGIC at hgic@clemson.edu or 1-888-656-9988.

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