The Castellón plain is an area cultivated for centuries, initially by rice fields and rainfed crops, and from the 20th century onwards mainly by orange trees. The low agricultural profitability is leading to an increasing abandonment of agricultural land, spontaneously colonised by vegetation. The colonising vegetation has a high synanthropisation rate, reaching 86 % in the driest areas. In wet areas, the ditches have allowed the original flora to survive, maintaining more native species, which also dominate in terms of cover. Almost a third of the flora is exotic, more than half of it naturalised species, and at least six considered invasive. It would be desirable to preserve or restore patches of natural vegetation between agricultural areas, to encourage the expansion of native flora on abandoned land. The advance of invasive species, which are particularly prone to spread in these areas, should also be controlled.