The past tense of spend money as if it grew on trees is spent money as if it grew on trees.

The third-person singular simple present indicative form of spend money as if it grew on trees is spends money as if it grew on trees.

The present participle of spend money as if it grew on trees is spending money as if it grew on trees.

The past participle of spend money as if it grew on trees is spent money as if it grew on trees.