How to Grow Purple Shamrock (False Shamrock)

closeup of purple shamrock

The Spruce / Kara Riley

In This Article

Purple shamrock (Oxalis triangularis), also known as false shamrock, is one of the uncommon plants with nearly black foliage. In reality, its foliage is a very deep purple color. The leaves are triangular and typically grow in groups of three. At night (or on particularly cloudy days) they fold up almost like an umbrella, but they open up again with the morning light. The plant bears tiny flowers that are a white to pale pink or lavender color. Purple shamrock is best planted in the spring and functions well as a houseplant. It has a moderate growth rate.

Botanical Name Oxalis triangularis (synonymous with Oxalis regnellii)
Common Names Purple shamrock, false shamrock, love plant, shamrock, wood sorrel, oxalis, black oxalis
Plant Type Perennial
Mature Size 0.5–1 ft. tall, 1–2 ft. wide
Sun Exposure  Full, partial
Soil Type Loamy, sandy, well-drained
Soil pH Acidic
Bloom Time Fall, spring, winter
Flower Color White, pink, lavender
Hardiness Zones 8–11 (USDA)
Native Area South America
Toxicity Toxic to people and animals
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Watch Now: How to Grow and Care for a Purple Shamrock Plant

Purple Shamrock Care

The purple shamrock is fairly easy to grow in the ground within its growing zones, as well as in containers and as indoor houseplants. The key to a healthy plant is providing it with a sunny spot and watering it whenever the soil starts to dry out. Also, plan to feed your shamrock throughout its growing season to encourage healthy growth.

It’s important to note that purple shamrock plants actively grow and flower during the fall to spring and go dormant in the summer. This might not happen every year, especially for houseplants, but it’s a possibility that requires some different care. When they are dormant, the foliage will degrade. If you see this occur, reduce watering and stop feeding your plant. As soon as you see new foliage begin to grow, resume your plant’s normal care routine.

closeup of purple shamrock looking more pink/purple
The Spruce / Kara Riley 
purple shamrock being grown in a container
The Spruce / Kara Riley 

Light

This plant grows well in full sun to partial shade. If you’re growing it outdoors and live in a hot climate, give it some protection from the hot afternoon sun. Indoors, the plant should be grown by a window that receives bright light. Regularly rotate the pot, so all sides of the plant end up facing the light and growing evenly. Too little light can cause the plant to become weak and leggy. 

Soil

The purple shamrock can grow in a variety of soil types as long as it has good drainage. Its roots are prone to rotting if the soil retains too much moisture. A loamy or sandy soil is best. And for container growth, a general, well-draining potting mix should be fine.

Water

Water to maintain an even amount of soil moisture on young purple shamrock plants. Established plants have some drought tolerance and are forgiving if you forget to water. During the growing season for purple shamrock plants, water whenever the top inch of soil has dried out. When the plant is dormant in the summer, lightly water about every two to three weeks to prevent the soil from drying out completely. 

Temperature and Humidity

These plants like temperatures between 60 and 75 degrees Fahrenheit, which makes them especially suitable to grow indoors in average room temperatures. They can tolerate nighttime temperatures down to 50 degrees Fahrenheit. Aim to protect the plants from strong winds outdoors and drafts indoors, especially those from air conditioners and heaters, as they can damage the foliage. A moderate humidity level is ideal for purple shamrock plants.

Fertilizer

Use either a slow-release or liquid fertilizer on the purple shamrock plant during its growing season. Indoors, a liquid fertilizer for houseplants is ideal. Mixing some compost into the soil also can help to promote healthy growth.

Is the Purple Shamrock Toxic?

Oxalis plants are toxic both to people and animals when ingested. All parts of the plant are poisonous, with the highest concentration of toxins being in the bulbs. 

Symptoms of Poisoning

Symptoms of poisoning both for people and animals include drooling, upset stomach, vomiting, diarrhea, weakness, lethargy, and tremors. Fortunately, the bitter taste of the plant usually deters a high level of ingestion that can cause serious symptoms. But still, if you suspect poisoning, contact a medical professional as soon as possible.

Shamrock Varieties

There are several plants that use the common name of shamrock, including:

  • Oxalis acetosella: Also known as the wood sorrel or shamrock, this plant has bright green, heart-shaped leaves that occur in groups of three.
  • Oxalis tetraphylla: This plant is commonly known as four-leaved sorrel or lucky clover because of its four split leaves. The leaves are bright green with a maroon center. 
  • Oxalis lasiandra: This species is referred to as the Mexican shamrock or palm tree oxalis. It grows a little over a foot tall and bears bright pink flowers to crimson flowers.
  • Oxalis adenophylla: This species is commonly known as the Chilean oxalis or silver shamrock. It features silvery green leaves and bears pink flowers with deep purple centers.
  • Oxalis bowiei: The common names for this species include the Cape shamrock, Bowie’s wood sorrel, and red flower wood sorrel. It bears rose-colored to reddish-purple blooms.