Oxalis Triangularis Plant Care at Home (Purple Shamrock)

If you’ve ever seen a floral display around St. Patrick’s Day, then you’ve likely seen an Oxalis triangularis plant in all its false shamrock glory. Although these plants are popular in March, they’re wonderful to grow any time of the year. Plus, they’re one of the easiest houseplants to keep alive. In this guide, I’m going to share how I care for my Oxalis triangularis at home, including the best soil types, watering frequencies, fertilizing needs, light exposures, and ideal environmental conditions for optimal growth.

Are False Shamrocks Easy to Grow at Home?

Out of all the houseplants in my collection, Oxalis triangularis is one of the easiest plants to grow indoors. I find that it’s relatively low-maintenance, tolerant of a variety of conditions, and is excellent for beginners.

What to Do Before Planting

Before planting a false shamrock, you’ll want to gather all the necessary supplies and choose a suitable location in your house for your new plant.

You’ll need a rich and well-draining potting mix, a container with drainage holes, and a location in your home that receives plenty of sunlight. I find that somewhere near a south-facing window is ideal. 

Although you could plant a false shamrock in a hanging planter, they aren’t really suitable for this type of container. They need a pot with drainage holes to prevent root rot and also don’t have much of a trailing habit.

I think they’re better displayed in a traditional container on a windowsill or side table.

Growth Expectations

If planting an Oxalis triangularis from a bulb, you should see growth above the potting soil within 3 to 6 weeks.

Mature false shamrock plants reach between 6 to 12 inches tall and 12 to 24 inches across.

The Best Soil Mix

False shamrock can thrive in acidic to neutral potting mix.

In my experience, when selecting or creating a potting mix for Oxalis triangularis, the most important thing to remember is that the soil must be well-draining and should have good aeration. Any potting mix that is too heavy will hold too much moisture and put the plant at risk of root rot.

Any rich, prepackaged, well-draining indoor plant potting mix will work well. I like to make my own soil mix at home (which is a fun and cost-effective project) by combining one part of potting soil with one part of sand, peat, or perlite. This provides excellent drainage, moisture retention, and aeration, as well as providing a stable base for the plant to grow.

Light Preferences

My Oxalis triangularis has grown happily in various light conditions, ranging from direct sunlight to partial shade. It will fare best, in my experience, in a location that receives plenty of filtered bright or medium sunlight.

I find that direct sunlight in the morning is best, ideally near an east-facing window, if possible. If your windows are more north-facing, then place them directly in front of the window to maximize light.

To encourage even growth, I rotate the pot 90 degrees weekly during the growing season.

Temperature and Humidity

My False shamrocks prefer temperatures between 65°F and 85°F. Do not expose the plant to temperatures below 60°F.

I find that moderate or average indoor humidity is fine. In exceptionally dry conditions, you can increase humidity by running a humidifier, misting the plant once a week, or adding a humidity tray with pebbles and water below the plant.

For ideal temperature and humidity conditions, try not to position your plant too close to any HVAC vents, drafty windows, or exterior doors.

How to Pot

I recommend choosing a well-draining container that’s about 1 to 2 inches larger than your false shamrock’s root ball. For added drainage, you can add a 1-inch layer of pebbles to the bottom of your pot, but this is not necessary as long as you use a well-draining potting mix and a pot that can drain as well.

Next, add a layer of potting mix to the pot, leaving enough room for about 1 inch of potting soil above your plant’s bulb and another inch or so of space between the top of the soil and the top of the container.

Place your plant’s bulb or rootball on top of the bottom layer of potting mix. Fill in around and over the roots and bulb with potting mix. Gently pat the potting mix down.

At this stage, I water the plant thoroughly until water drains from the bottom of the pot. Plus, I allow all excess water to drain before placing your plant in the desired location.

Watering

My Oxalis triangularis prefers even, constant moisture but is especially susceptible to root rot and damage from sitting in soggy soil. I’m extra careful not to overwater these plants.

During the growing season (spring and summer), I water my false shamrock when the top inch of soil feels dry – about every one to two weeks. During the dormant season (fall and winter), I water my false shamrock when the soil is about halfway dry – every two to three weeks.

My favorite technique is to simply feel the potting mix with my fingers to test the moisture level. Another option is to use a moisture probe, which simplifies the watering process (especially during dormancy).

Be aware that you might need to adjust this watering schedule depending on your plant’s environment. Plants that receive more sunlight or that are in warmer, more arid locations will require more frequent watering. If your home is especially dry, you might consider misting your plant every couple of weeks.

Conversely, plants that receive less sunlight or that are placed in cooler or more humid environments will require less frequent watering.

While false shamrocks can usually tolerate tap and well water, you can safeguard your plant’s root system from chemicals and heavy metals by using filtered water or collected rainwater. It’s best to use water that is at room temperature rather than extremely cold or hot water that can shock the roots. Personally, I let a jug of tap water sit out over night to allow the fluoride to settle a little before I water my plants.

Fertilizing

Plenty of nutrients in your plant’s potting soil will encourage growth and flowers. I only fertilize an Oxalis triangularis plant during the growing season.

I use a balanced liquid houseplant fertilizer diluted to half-strength every one to two weeks. For best results, add the fertilizer to your regular watering routine when appropriate.

Pruning

In my experience, False shamrocks don’t require the same pruning that other types of houseplants need. Rather than pruning your plant to control its growth and shape, I simply prune an Oxalis triangularis to remove spent flowers and withered leaves to protect the plant from harmful bacterial growth.

I also make sure to use sterile pruning shears or scissors to snip away spent flower or leaf stalks as close to the base of the plant as I can.

Propagating

During Dormancy: 

I find that when the plant is at least two weeks into its dormancy period, it can propagate by splitting the bulbs. I remove the plant from its pot, divide the bulbs and roots, keeping as much of the root material intact as possible. I then repot them into separate pots, water well, and watch them sprout in spring.

During the Growing Season:  

You can also propagate a false shamrock during the growing season by dividing the plant. Remove the plant from its container and gently tease apart separate bulbs and roots. Repot the separate halves, thirds, or fourths of the plant in their own containers and water thoroughly.

Repotting

I find that my Oxalis triangularis needs to be repotted every one to two years to refresh the plant’s potting mix and accommodate new growth.

Repotting a false shamrock during the growing season can shock the plant. So, I recommend repotting in the middle of dormancy.

To repot your false shamrock, I choose a well-draining container that’s one to two inches larger than the plant’s current pot. I use a soil mix that’s similar to the plant’s current mixture.

Common Problems and How to Treat Them

Weak and Leggy Stems

In my experience, long, weak stems usually occur as a result of too little sunlight. Move your plant to a sunnier location or add a fluorescent lamp.

Yellow Leaves and Mushy Stems

I find that this is a tell-tale sign of root rot, which occurs due to overwatering.

If this occurs, I recommend repotting your plant and removing any rotted portions of the roots. Make sure you choose a well-draining potting mix and a well-draining container. If necessary, reduce watering frequency and/or volume.

Brown, Wilting, or Crispy Leaves

This is a sign of too little moisture. You might need to increase your watering schedule or add more humidity to the environment.

No Growth

Growth stops during dormancy. So, it’s normal for there not to be any new growth in fall and winter.

All About Oxalis Triangularis Plants

Oxalis triangularis, commonly called false shamrock or purple shamrock, belongs to the Oxalidaceae (wood sorrel) plant family. There are about 560 species of plants in the Oxalis genus, and Oxalis triangularis is one of the most popular thanks to its lovely purple foliage.

They are herbaceous perennials that grow from unique bulbs called corms. They have delicate, five-petaled pink or white flowers and foliage that varies in colors including deep, almost-black purple, red, green, and combinations of green and purple. Both the plant’s foliage and flowers are responsive to sunlight, opening during the day and closing in the dark.

Native to Argentina, Bolivia, Brazil, and Paraguay, Oxalis triangularis can be grown outdoors in USDA climate zones 8a through 11. However, it is most popularly grown as a houseplant.

Why Is Oxalis Triangularis Called False Shamrock?

Oxalis triangularis is commonly called the false shamrock because it is often confused for the true shamrock plant (Trifolium) due to its trifoliate leaves.

False Shamrock Adds True Beauty to the Home

False shamrock is low-maintenance and beautiful to grow. Whether you add a few to your home or a single Oxalis triangularis to a prominent, sunny location, you’ll enjoy its foliage and petite blossoms for years to come.

Further reading: Discover an amazing collection of purple houseplants you can grow at home.