The common birdsfoot trefoil, known in Maltese as qrempuċ tal-mogħoż, is an annual plant that produces small, yellow flowers in winter and spring.
It belongs to the leguminous family in which we also find important members such as beans, peas and sulla (silla), as well as a large number of indigenous and alien wild plants.
Leguminous plants are found on all continents, except on Antarctica, and in most terrestrial habitats. The family consists of about 19,400 species; nearly 110 of these have been recorded in the Maltese islands.
Legumes have been utilised by man since the earliest times. Common and broad beans have been cultivated for nearly 8,000 years in Europe, Asia and in the Americas.
The flowers of the typical legume develop into a simple fruit known as a legume (miżwet). When mature, the dry legume splits open along a line of weakness to release the seeds. Beans and pea pods are typical legumes.
Leguminous plants are also well known for being able to utilise atmospheric nitrogen. They do this by forming a symbiotic relationship with nitrogen-fixing bacteria which live in structures known as root nodules.
The bacteria convert the nitrogen into compounds which can be utilised by the plants. The availability of a good source of nitrogen compounds allows leguminous plants to synthesise amino acids which are the building blocks of proteins, making leguminous plants a good source of proteins.
Furthermore, when leguminous plants die and decompose, their nitrogen compounds enrich the soil and become important components of crop rotation systems.
In crop rotation, farmers alternate non-legumes with leguminous plants. A typical rotation in Malta would be a crop of potatoes, followed by onions and then sulla.
Crop rotation was widely practised in the past but nowadays farmers prefer to use synthetic fertilisers which sometimes cause more harm than good.