Mexican bird of paradise, known botanically as Caesalpinia mexicana, is a yellow flowering evergreen shrub or small tree in the pea family of plants. It thrives in the semi-tropical and tropical climates of USDA zones 10b and 11. Pruning is only required to remove damage and control spread, if desired. According to the University of Arizona, pruning can also be employed to create a more classical tree form out of the natural shrublike habit.
Prune away any broken, dead, cracked, diseased or abrading branches or any branches that are dragging or lying on the ground soil throughout the year as you spot them. Cut back to a point of healthy wood or remove the branch entirely, severing it at the crown just above the soil and pulling it from the canopy.
Prune your Mexican bird of paradise for size or shape in the fall or early winter after blooming has finished for the year. Shear back the branch tips to the desired length to control the height and spread. Follow the natural line of the shrub for a professional result.
Refrain from pruning the shrub until late fall or early winter after the seed pods have developed and matured, if you want to collect seed for propagation or allow self-sowing.
Create a tree form by pruning away all the branches that emerge from the trunk roughly one-third to halfway up from the ground. Prune away any new branching or water sprouts below this line as needed to preserve the bare-trunk tree form. Make cuts roughly flush with or close to the trunk to prevent gouging into and damaging the trunk cambium.