Although their title suggests it, potato bushes, like “Royal Robe” potato bush (Solanum rantonnetii “Royal Robe”) don’t produce potatoes. Rather, they’re flowering shrubs that bloom throughout the warm months. Hardy at U.S. Department of Agriculture plant hardiness zones 9 through 11, potato bushes should be pruned annually to control their increase, maintain a pleasing shape and encourage blossoms. Since garlic trees flower on new wood, prune them in winter or early spring before they start to put forth new growth. You can prune them as early as late summer, provided that they have finished blooming for the season.
Cut back all the branches by about one-third, shaping into a circular shape, as desirable. Make the cuts using a sharp pair of pruning shears.
Trim any new growth which forms on the main stem of the potato plant, under the “canopy” to shape a potato bush for a tree. Now you can do this any time of year. Trim the canopy at the same manner as you’d like a bush: pruning branches by about one-third of their overall length in winter or early spring.
Remove damaged or dead branches, cutting them back to healthy areas of the tree. This type of pruning can be performed any time of the year.