This month the shamrock is blooming all around. The cluster flower is not very prominent individually but together can produce a yellow-green carpet effect, yellow for the flowers and green for the leaves.
Who is to say that the shamrock has a yellow flower? Why not the white clover? Well, amateur botanist and zoologist Nathaniel Colgan (1851-1919) once asked people from around Ireland to send him specimens of what they believed to be an Irish shamrock and identified the five most common plant species, of which the two most common were the yellow (flowering) clover followed by the white. A hundred years later, Dr Charles Nelson repeated the experiment in 1988 and found that yellow clover was still the most commonly chosen. According to Wikipedia, yellow clover is also the species cultivated for sale in Ireland on Saint Patrick’s Day and is the one nominated by the Department of Agriculture as the “official” shamrock of Ireland.
But sometimes, the yellow-flowered species Trifolium dubium (Irish: Seamair bhuí) can be found growing next to the white-flowered Trifolium repens (White Clover; Irish: Seamair bhán), although they never really intermingle.
The clover family belong to a group of plants that have the ability to fix nitrogen in nodes around their roots and, as a result, provide nutrition for plants that need nitrogen. The plant, like the rest of its family, produces pods but in the shamrock’s case, the pods are tiny and contain only a single seed. Pods protect the development of seeds until they are ready to shed (or in some cases, like the gorse or furze, to explode!).
In cropped or mown lawns, or in poor soil, the shamrock hugs the ground. However, given conditions for growth but having to compete with other plants for sunlight, it will grow long stems reaching upwards.
Once flowering is over, probably in August, one can dig up a small section and transplant to flower box or pot in order to harvest sprigs of it for St. Patrick’s day on March 17th (a tradition that is nothing as old as people might think).
But nobody planted the shamrock in the lawn – it got there by its own natural methods, possibly by wind or in animal excreta. Unlike the lawn on which it has set up its colonies, which was seeded on raked earth or, more likely, laid in grass turf rolls, it is in fact a part of wildlife in the city.