Will the real four-leaf clover please stand up?!

February 27, 2020

There are many plant species bearing the iconic clover look in the Dallas-Fort Worth Metroplex. The true lucky clover is believed to be the white clover of the legume family - Trifolium repens. Although Trifolium is derived from the Latin words tres (three) and folium (leaf), a unique genetic mutation causes some plants to grow an additional leaflet! A simple Google search will tell you the likelihood of a four-leaf clover is 1 in 10,000. However, it was not until 2017 that a study was conducted by enthusiasts to see if this number was accurate. They found the frequency to really be 1 in 5,076! This is not the only surprise this species brings to the table. Some of these plants across the world not only grow one extra leaflet, but sometimes up to 8 leaflets. There is even a Guinness World Record for the largest number of leaflets on Trifolium repens. A man in China has been record-holder with his discovery of a plant with 56 leaflets!

When BRIT moved into its current building in 2011, a population of Trifolium repens was planted on the southwest side of the building near the path and geology wall. Several BRIT staff members and volunteers have discovered a few lucky clovers from this population over the years! The herbarium staff decided it would be interesting to conduct our own survey by looking into the collections to see if any botanists had either purposefully or accidentally collected four-leaf clovers on sheets of Trifolium repens.

Of the 556 total sheets of Trifolium repens from the BRIT/SMU, VDB, and NLU collections spanning over 150 years and almost every continent, only 6 lucky clovers were discovered! So, only 1.08% of the Trifolium repens sheets in the entirety of the BRIT Philecology Herbarium contains a four-leaf clover. It is possible there are more, but depending on how the original collection was pressed, some sheets were difficult to determine with a large patch and overlapping leaves. 

This is a close up of an image of a Trifolium repens sheet from the NLU collection. Collected by  Jack Kenney (#54) on April 24, 1969 in Catahoula Parish, Louisiana.
This is a close up of an image of a Trifolium repens sheet from the NLU collection. Collected by Jack Kenney (#54) on April 24, 1969 in Catahoula Parish, Louisiana. Two four-leaf clovers were collected and pressed.

What makes Trifolium repens different from other clovers growing around us? How can we tell them apart from other clover species before we start hunting for lucky clovers? Herbarium specimens, iNaturalist, and the Shinners and Mahler's Illustrated Flora of North Central Texas are all great resources for aiding in the identification of species and illumination of what flora lives with us in our little home of North Central Texas.

The white clover, Trifolium repens, can be found in dense mats or patches along roadsides, lawns, and disturbed areas. This is a common "weed" to most people! The white to pinkish clustered flowers are bee-pollinated, and the leaflets have a distinct white crescent on the upper sides. Once you've come across a population, scan your eyes across the area for the lucky clover - don't count every leaf of every individual! When our eyes are fixated on the patterns of the three leaves and we scan a patch, any four-leaf clover shape and symmetry will stand out! Once you've spotted one four-leaf clover, there's a better chance you'll find more in that same area. 

Trifolium repens
White clover observed and photographed by Ashley Bordelon. Observation on iNaturalist can be found here: https://www.inaturalist.org/observations/20699702

 

In North Central Texas, there are at least twelve species of Trifolium clovers. Each species varies in flower color, leaf sizes, and habitat. Rather than looking into all of the Trifolium species in detail, I will highlight below other species commonly referred to as "clovers."

Always-Three-Leaf Clover Species:

  • Creeping Woodsorrel (Oxalis corniculata)
    • The creeping woodsorrel can be found growing in disturbed or cultivated areas, so be sure to check your sidewalks, backyards, and flowerbeds! The word "creeping" in the common name refers to the way the stems creep along the ground. The leaves resemble hearts, and the flowers are yellow. Sometimes the leaves can have some purple pigmentation.
Oxalis corniculata
Creeping woodsorrel observed and photographed by Bob O'Kennon. Observation on iNaturalist can be found here: https://www.inaturalist.org/observations/10575672
  • Spotted Bur-Clover (Medicago arabica
    • Have you ever walked across an open field only to find later your socks and shoes are covered in burs? While there are some grass species that produce burs, species of Medicago do as well! The fruits are tiny, prickly, and recurved. They will always have one central, purple-red spot (sometimes appearing heart-shaped) on each leaflet. The spotted bur-clover grows just about anywhere it can - from lawns to roadsides. 
Medicago arabica
Spotted bur-clover observed and photographed by Ashley Bordelon. Observation on iNaturalist can be found here: https://www.inaturalist.org/observations/39731022
  • Yellow Sweetclover (Melilotus officinalis
    • The sweetclover is easier to tell apart from some of the other species mentioned. Rather than a low ground-creeping species, it stands up to 2 meters tall! You are likely to notice the elongated, yellow inflorescences before you see the more slender leaflets of the clovers below. 
Melilotus officinalis
Yellow sweetclover observed and photographed by Bob O'Kennon. Observation on iNaturalist can be found here: https://www.inaturalist.org/observations/25828311

Always-Four-Leaf Clover Species:

  • Water Clover or Pepperwort (Marsilea vestita)
    • Water clovers are not flowering plants, but ferns! These will always be found growing in aquatic or wet habitats, near rivers, or wet depressions. The leaves are accompanied by small oval-shaped sporocarps (spore-producing structures) growing at the base of the petiole near the rhizomes. The pinnae, or leaflets, can vary by millimeters in length and width. 
Marsilea vestita
Water clover observed and photographed by Ashley Bordelon. Observation on iNaturalist can be found here: https://www.inaturalist.org/observations/28813331
  • Iron Cross (Oxalis tetraphylla)
    • You are not as likely to find this in the wild but rather sold in plant nurseries. I've included it in this list because it could escape from cultivation or you may be curious to see another clover plant used as an ornamental! The "Iron Cross" has four heart-shaped leaves with dark purple splotches near the center and bright pink flowers. 
Oxalis tetraphylla
Oxalis tetraphylla grown in cultivation. 
 

Life is short - walk a little slower, look down at the ground, learn about and appreciate all of our little green friends. Most of the species mentioned above can be found in your backyards and neighborhoods! You don't need to go far to run into nature. 

Have you spotted a clover that you can't key out? The botanists at BRIT are here to help! Click here to fill out a Plant Identification Form and email plantid@brit.org.

 
 
 
Sources:
Diggs, George M., et al. Shinners & Mahlers Illustrated Flora of North Central Texas. Botanical Research Institute of Texas, 1999.
“How Rare Are Four-Leaf Clovers Really?” Sharetheluck, Share the Luck | Our Vision, 24 July 2017, www.sharetheluck.ch/single-post/How-rare-are-four-leaf-clovers-really.
“How to Find a Four Leaf Clover.” Sharetheluck, 2016, www.sharetheluck.ch/finding-a-4-leaf-clover.
“INaturalist.” INaturalist, www.inaturalist.org/.
“Most Leaves on a Clover.” Guinness World Records, 2009, www.guinnessworldrecords.com/world-records/most-leaves-on-a-clover/.
“Oxalis Tetraphylla 'Iron Cross' (Good Luck Plant).” Gardenia.net, www.gardenia.net/plant/oxalis-tetraphylla-iron-cross.

 

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