Rijstgras [Leersia oryzoides (L.) Swartz] in het Middennederlandse rivierengebied

Leersia oryzoides has declined probably less dramatically than was assumed.² This freatophitic species is easily overlooked because its vegetative parts appear late in summer, and its inflorecences come out of the sheaths in warm summers only. In the region Vijfheerenlanden (province of Zuid-Holland) it is found in 29 kilometer squares in the period 1992—1994. Its occurrence seems to be related to the presence of bare places and steep banks of ditches with a southern exposition, as well as of seepage water. It is likely that its present distribution is larger than presented in Figure 1.