We don't have synonyms for regrowing yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are growing, reproving and ingrowing.
(n) :
(agriculture, ecology) The self-cultivation of vegetables by city dwellers, using flower pots and windowsills, growing them from roots, cuttings, and scraps, for recycling and sustainable living.
(n) :
(agriculture, ecology) The self-cultivation of vegetables by city dwellers, using flower pots and windowsills, growing them from roots, cuttings, and scraps, for recycling and sustainable living.