Goji berries (Lycium barbarum) are an ancient Chinese crop with small tasty fruit that your kids will love to snack on. The plants make a tough, low-maintenance hedge about 5 to 8 feet tall that can be grown in U.S. Department of Agriculture plant hardiness zones 5 through 9. You don't need to prune goji berries for ample fruit production, but they have a rather sprawling habit and look much better with a regular trim.
Decide if you want the plants to grow as a dense hedge or as an open, airy shrub. A hedge form looks best with a continuous line of gojis planted about 3 feet apart and pruned together in a uniform shape. An open form is better suited for a single plant.
Start pruning goji plants when they are young to encourage a base structure of short, thick stems, whether for hedges or single specimen plants. Don't be afraid to cut them back hard -- long lanky stems can be pruned back up to 75 percent of their length for hedges and 25 to 50 percent for an open shrub form. Cut back to just above a leaf bud using a 45-degree angle cut. Doing this form of heavy pruning during the winter dormant season will stimulate a strong growth response in spring and lead to a more compact, attractive growth habit.
Prune all branches back to a consistent length based on the desired shape for hedges. A hedge that is bit taller than wide is a nice match for the growth habit of gojis -- an upright rounded shape 3 feet wide by 5 feet tall works well. When they are young, maintain proportionally smaller dimensions with pruning, and gradually increase the size of the hedge until the maximum desired height is reached. This needs to be done at least three or four times during the growing season to maintain a uniform shape.
Lightly prune back the tips to form a roughly symmetrical shape for open, airy shrubs, but allow some branches to be a little longer than others for a more carefree look. Aim for a mature height of 6 or 7 feet tall and 4 feet wide, and maintain the same proportions in a smaller form with young plants as they grow. Prune out dense branches in the interior of the shrub, as well. Remove those that cross toward the center, and cultivate a vase-like shape with evenly spaced branches that splay loosely outwards from the central branch structure. Prune in the winter, and let the supple spring growth arch toward the ground.
Remove any "suckers" that sprout from the roots around the plant to maintain the clean aesthetic of single-trunked shrubs. This type of pruning can be done at any time of year.