Salt or sodium chloride is usually poison for plants. Salt simply sucks the water out of the plant. The high salinity of the beach sand means that ordinary plants do not thrive there. Only the so-called salt-tolerant plants can grow on the beach.
A plant can only absorb water when the osmotic pressure in the plant is greater than in the ground water. Then a physiological process causes the water to be “sucked” into the plant. Beach plants have an osmotic pressure of 17-36 atmospheres, which 4 times than in glycophytes, the plants that are not salt-tolerant. The beach plants build up the high osmotic pressure by absorbing salt from the ground water that accumulates in the plants.
Beach mustard can form quite large, contiguous stands on the beach and is common throughout Denmark. The herb usually grows on sandy beach shores where it finds nourishment from washed-up seaweed. The flowers of the herb are violet and fragrant. They have four petals forming a cross and are gathered in small bunches. The fruits are green siliques with two parts, the top falls, while the bottom remains on the plant.
Did you know?
Beach mustard, which grows in North and West Jutland, does not have deeply cut lobed leaves like the plants that are found in the rest of the country have. The leaves of beach mustard from the north-west of Jutland are wider and roughly toothed or lobed.