Method of supporting plant growth using polymer fibers as a soil substitute

Fiberballs, comprising:

• biodegradable polymer fiber having a cut length of about 0.5-60 mm, each fiberball having an average dimension of about 1 to 15 mm, at least 50% by weight of the fiberballs having a cross-section such that its maximum dimension is not more than twice its minimum dimension, and the polymer is a copolymer of poly(ethylene terephthalate) and diethylene glycol or a non-aromatic diacid, and an alkali metal or alkaline earth metal sulfo group.