The white wall rocket is a very common annual plant. It grows in disturbed habitats such as uncultivated fields and roadsides. Despite or because of the fact that it is very common few people actually take enough interest to look closely at the flowers.
The flowers are white sometimes with a tinge of violet. Their structure is similar to that of other members of the mustard family to which the rockets belong. It is made up of four petals arranged in the form of a cross. The family is also known as the crucifers, meaning cross bearing, or sometimes as the cabbage family.
After having lain dormant for a whole summer, the seeds of the white rocket sprout quickly soon after the first autumn rains. Within weeks the plant starts flowering.
The white rocket is native to southern Europe and the Mediterranean. Probably as a result of climate change it is now found further north and has even reached southern England.
The crucifer family is of importance because several species have been cultivated for thousands of years.
Members of the family include the cabbages, broccoli, cauliflower, turnip and mustard. The leaves of the white rocket are similar to those of the cultivated rocket and they are sometimes added to salads to add a spicy taste. The leaves are said to have diuretic properties but it seems that the plant is not used medicinally.
Many species of crucifers are food plants for the caterpillars of various species of white butterflies including the small and cabbage whites which can become pests of cultivated plants.
Members of the crucifer family are characterised by fruit in the form of a capsule known as a siliqua. The siliqua is an elongated structure with seeds inside. The capsule breaks open along a line of weakness in dry condition. In some species the siliqua breaks open explosively and the seeds are thrown far and wide away from the parent plant.
This article was published in the Times of Malta on 18 December 2013.