How to Prune Mexican box elder?
Little pruning is needed. Remove diseased, damaged, crowded or crossing shoots and unwanted growth. If needed, Prune only from late autumn to midwinter.

Mexican box elder · Acer negundo subsp. mexicanum
Grow in any moisture-retentive, well-drained soil in sun or partial shade. Leaf scorch can be caused by lack of soil moisture or excessive exposure. See tree cultivation
Little pruning is needed. Remove diseased, damaged, crowded or crossing shoots and unwanted growth. If needed, Prune only from late autumn to midwinter.