PROBLEM TO BE SOLVED: To provide a low-temperature insulator which can be withdrawn after use and is reusable as a water holding material for plant growing and to provide a method for reusing it. SOLUTION: The low-temperature insulator comprises a water absorbing resin(A) which absorbs calcium ion of 0-100 mg per dry weight of 1 g and can absorb 10-1,000 times water in an ion exchanged water at 25°C, and, preferably, whose chlorine ion content is 0.07-7 mmol per dry weight of 1 g; the water holding material for plant growing which is prepared by using the low-temperature insulator after use; the method for reusing the said low-temperature insulator by withdrawing after use and reusing it as the water holding material for plant growing. COPYRIGHT: (C)2004,JPO
