The term 'WATERSIDE PLANT' can be summarized by two crossword solutions: RUSH (4 letters) and SEDGE (5 letters). A RUSH is a type of aquatic plant that grows in shallow water or on the banks of rivers, lakes, and ponds. Rushes are often used to make baskets, mats, and other items. SEDGE is another type of waterside plant that is similar to grass but has triangular stems. It is often found in wetlands and is used for erosion control and as a food source for wildlife.