Burr Clover: Love it or hate it!

Wildlife and livestock of all kinds relish the proteinrich leaves of Burr Clover. Here, my chickens are enjoying a spring feast! (Robert Benson photo)

Burr Clover is a fast-growing legume that “graces” our lawns, gardens, and flower beds in early spring. Four to five tiny yellow pea-like flowers combine to make a coiled spiral seed pod or burr. The edges of this burr are covered with prickles with hooked tips. Burr Clover’s seed pods readily tangle in fur and clothing. (Wikimedia Commons photos)

BRUSH COUNTRY BACKYARD

As wintery days begin to be overtaken by sunny springlike days, you will notice a distinct greening up of our pastures, yards and gardens. The rich, green ground cover billows over any available space, including dormant vegetable gardens and flower beds. You may love it, as I do, for its vibrant color and rude good health, or you may hate it as a fast-growing weed. There seems to be no “in-between” sentiment.

This “love it or hate it” plant is Burr Clover (Medicago polymorpha). It is native to the Mediterranean region but has been introduced worldwide. Since it is not naturally found in North America and because it grows so readily, it could be described as “invasive.” However, I think the real reason many people hate Burr Clover is the prickly dried seed pods that the plant bears. The pods are coiled spirals – each coil about a quarter of an inch in diameter, not counting the two rows of prickles along the edges. A pod typically has two to five coils compressed together to resemble a little wheel. This is the burr that catches in clothing, fur and plants. It is not as painful as a sticker burr (the bane of barefoot children!) but is annoying. You can spend half of the summer picking the burrs out of the fur of long-haired pets.

Of course, the burr is nature’s way of transporting seeds to new locations. Thus, seed dispersal is easy for Burr Clover. Even if the seed pods do not migrate away from the parent plant, the seeds will germinate right under the dead plant next spring. Wherever you have Burr Clover this year, you are sure to have it the following year. And from then on!

However, Burr Clover has many benefits. It is highly palatable to livestock and wildlife. Thus, it is a valuable nutritious forage plant for grazing animals. This is why Burr Clover was planted around the world. It is agriculturally a very welcome plant. As a winter ground cover, it secures the soil from erosion and puts nitrogenous compounds into the ground. As a natural fertilizer, it reduces the need for synthetic fertilizers.

How can this be? Burr Clover is in the Legume Family, which is also known as the Fabaceae or Bean Family. Legumes are particularly valuable plants in that they form a symbiotic relationship with certain soil bacteria. The bacteria live in nodules on the roots where they are sheltered; in turn, the bacteria “fix nitrogen.” To “fix nitrogen” means that nitrogen gas from the air is combined with hydrogen to make ammonia. This is the first step in protein synthesis. The ammonia is further processed to make nitrogenous compounds and, eventually, amino acids and proteins. Plants cannot take in nitrogen in its elemental form; the gaseous nitrogen is not absorbed. However, the legume can absorb nitrogen once nitrogen is chemically combined with hydrogen (or oxygen). Some of these nitrogen compounds leach from the legume’s roots and fertilize surrounding plants. If the roots are left to decompose in the soil, the nitrogen is available for subsequent crops.

Burr Clover is a protein-rich food source for grazing animals. It puts a natural fertilizer back into the soil. The clover’s spreading mats of vegetation help to control erosion. It is a pretty green. I like it!

Burr Clover is a non-native plant that can grow out of control. It produces an abundance of prickly burrs that catch on fur and clothing. It is a nuisance in our flower beds and gardens. Many people hate it.

Where do you stand on the subject of Burr Clover?