PROBLEM TO BE SOLVED: To construct a vegetation installation on water, capable of maintaining natural environment well. SOLUTION: This vegetation installation has a first concave member 4, a second concave member 30 and a plurality of vegetation members 3 placed on the opened surface 13 of the first concave member 4 and covered by the second concave member 30. The first concave member 4 has a buoyancy-causing part 15 for causing the buoyancy when placed on the water, and the concave part to be charged with vegetation substrate. The plurality of vegetation members 3 are connected to each other through connecting members 45a to 45c. The first concave member 4 and the second concave member 30 have holes 8 and 34 in the walls 7 and 33 forming the concaves respectively.
