PROBLEM TO BE SOLVED: To provide a connective material capable of mutually connecting by a simple means lightweight planting blocks enabling a plant to be raised without using soil and therefore suitable for use on a building rooftop, veranda or the like. SOLUTION: This connective material 10 comprises an upper half member 10U having a press piece 11 and a tightening bolt 12 and a lower half member 10D having legs 14 and a tightening screw rod 15 on a disc 13, being designed in such a way that the leg 14 is inserted from the reverse side into a hole 6a of a connective site 6 at the corner of a plantation block A, and the tightening bolt 12 and the screw rod 15 are screwedly engaged with each other to tighten and fix the planting blocks with each other.
