What does ARBOR DUM CRESCIT, LIGNUM CUM CRES- CERE NESCIT mean?

ARBOR DUM CRESCIT, LIGNUM CUM CRES- CERE NESCIT meaning in Law Dictionary

[whatever is] a tree whilst it develops, [is] lumber with regards to ceases to grow. Cro. Jac. 100; Hob. 77&, in marg.