Oxalis ‘Purple Shamrock’: This Plant Needs A Period Of Dormancy And Occasional Feeding
Elizabeth is a Permaculture Garden Designer, Sustainability Consultant and Professional Writer, working as an advocate for positive change. She graduated from the University of St. Andrews with an MA in English and Philosophy and obtained a Diploma in Applied Permaculture Design from the Permaculture Association.
Reviewed By ROY NICOL
Roy is a Professional Gardener and Horticultural Consultant, specialising in large garden year-round maintenance and garden development. He is an RHS Master of Horticulture and uses his research in the application of no-dig methods in ornamental garden settings. Roy has been a Professional Gardener for more than six years and is a member of the Chartered Institute of Horticulture, Professional Gardener's Guild and Association of Professional Landscapers (Professional Gardener).
Shamrock is the name given to several three-leaved plants within the Oxalis genus as well as clover (Trifolium repens) and medick (Medicago lupina), Oxalis bein, popular for their three-four lobed clover-like leaves and star-like flowers, which are grown as houseplants in the UK.
These plants, popular as St. Patrick’s Day decoration, are considered lucky by some.1DiLonardo, M. (2021, February 8). 17 Things You Didn’t Know About Shamrocks. ThoughtCo. Retrieved March 21, 2023, from https://www.thoughtco.com/things-you-didnt-know-about-shamrocks-4863451
They are attractive and interesting plants that could be interesting additions to a houseplant collection.
In this article, we will focus on the most popular Shamrock or False Shamrock houseplant, Oxalis triangularis.
Overview
| Botanical Name | Oxalis triangularis |
| Common Name(s) | False Shamrock / Purple Shamrock |
| Plant Type | Bulbous perennial |
| Native Area | South America |
| Hardiness Rating | H3 |
| Foliage | Deciduous |
| Flowers | Pink and white star-shaped flowers |
| When To Plant | Any time if growing indoors, Spring if outdoors |
Sunlight
Preferred
Partial Shade
Exposure
Sheltered
Size
Height
0.1 – 0.3M
Spread
0.1 – 0.5M
Bloom Time
Summer / Autumn
Soil
Preferred
Loam, clay or sand
Moisture
Moist but well-drained
pH
Any
Native to South America, this is the plant commonly referred to as false shamrock or ‘shamrock plant’.2Oxalis triangularis. (n.d.). North Carolina Extension Gardener Plant Toolbox. Retrieved March 21, 2023, from https://plants.ces.ncsu.edu/plants/oxalis-triangularis/
The subspecies O. triangularis subsp. papilionacea, AKA the ‘Purpleleaf False Shamrock’, has been gifted the RHS Award of Garden Merit.
This is a bulbous perennial plant with deep maroon, clover-like leaves and white or pale pink, five-petalled little flowers.
This may also sometimes be grown outside in the warmest areas, but is also most commonly grown as a houseplant.
One very interesting thing about this plant is that the leaves, when examined closely, look like an umbrella during the night or when disturbed, and the flowers also close during the night.
It also, unlike most other common houseplants, goes through a period of dormancy each year.
Habitat & Growing Conditions
Temperature
False Shamrock has a H3 hardiness rating and should be grown in temperatures of around 15°C.
It will cope with higher temperatures but will tend to suffer if temperatures above 25°C are sustained for too long.
It can tolerate temperatures down to around -3°C and will only survive winter outdoors in the very mildest regions of the southern British Isles, in a particularly sheltered spot.
Usually, therefore, these plants are grown undercover, or as houseplants here in the UK.
Sunlight
These plants require a position with bright yet indirect sunlight indoors.
Outdoors in a suitable spot they will thrive in partial shade.
When not grown as year-round houseplants, these plants are sometimes also placed outdoors in late spring in partial shade, then moved back indoors or undercover into frost-free conditions in early autumn.
Soil Requirements
In terms of the growing medium, ‘False Shamrock’ needs moisture-retentive yet well-drained soil.
A recommended mix for this plant is 1/3 loam, 1/3 leaf mould and 1/3 grit, or, alternatively, an equivalent soil-free compost.
Ongoing Care
Dormancy
‘False Shamrock’ can be an unusual plant, and many used to growing other houseplants may find them rather different from the other plants they may have grown.
The main difference is that as corms, these plants have frequent periods of dormancy, which can occur during winter but may also occur 2-3 times a year if Oxalis is grown undercover.
Those who are not familiar with these plants may often fear that their plants are unwell, as they seem unhealthy and begin to lose their leaves, but this is a natural part of the plant’s life cycle.
The plant needs a period of rest.
Leaves should be allowed to die back naturally, and the corms should be left to the dormancy period for 3-4 weeks when it occurs in the summer months, or overwinter in those with winter dormancy.
Watering
These plants should be watered in moderation while they are in active growth, taking care not to cause waterlogged conditions, yet also ensuring sufficient moisture.
However, when the plants are dormant, watering should be minimal and the growing medium should be kept barely moist.
Feeding
During periods of active growth, it is a good idea to feed these plants with a balanced, organic liquid plant feed (such as a compost tea) every month or so.
However, during dormant phases, feeding should be halted entirely.
Propagation
Oxalis triangularis can be propagated by means of seed or division.
Seeds are best sown as soon as they become mature, in a cold frame or indoors.
Note, however, that the seeds of certain subspecies may not come true.
This could be interesting, since you may have, for example, purple-leaved types growing from the seeds of a green-leaved form – so you might wish to experiment.
Prick out the seedlings into individual pots and grow them indoors, planting out or placing them outdoors in late spring or early summer if you wish to do so.
Division is best carried out in spring.
Pot up smaller divisions and grow them on in a cold frame or under cover even when planning to place them outdoors, so they are well established.
Larger divisions can be placed into an outdoors position right away if they are to be grown outdoors.
Common Problems
Generally, oxalis are relatively untroubled by pests and diseases.
However, they can be troubled by slugs and snails when placed outdoors, and can sometimes be susceptible to rust diseases, which can be unsightly, though these fungal infections will rarely kill your plants.
Aside from understanding dormancy, oxalis houseplants are fairly easy to care for and they do not require pruning.
In general, you should find false shamrock plants interesting and relatively straightforward additions to a houseplant collection.
