Fruitless mulberry trees include the "Fruitless" cultivar of the white mulberry (Morus alba "Fruitless") or male selections of white mulberry cultivars, including "Stridling," "Kingan" and "Urban." Landscapers prefer fruitless mulberry trees over fruiting varieties because they provide the same shade benefits without the mess associated with dropped fruits. Fruitless mulberry roots are potentially invasive and should be planted away from septic systems and sidewalks. You can cut back the fast-growing fruitless mulberry in a process called pollarding to encourage a full round canopy and prevent fruitless mulberry trees from outgrowing the landscape.
The fruitless mulberry is cut back to leave three to six main branches stemming from the trunk and all lateral or secondary branches are removed. The main branches are also cut back, leaving stubs only a few feet in length. Each spring, new growth shoots sprout from the pollard heads also known as knobs at the end of these main branches. Repeat the process every one or two years, removing all of the new sprouts back to the knobs.
Fruitless mulberry trees are incredibly fast-growing trees. A mature tree left unpruned can grow 30 to 50 feet tall and quickly take over a small landscape space. Pollarding allows you to restrict the tree's size so it only grows as tall and wide as the growth of its new shoots. Landscapers similarly use this technique for other fast-growing trees, including willows and crepe myrtles. This is an extreme pruning method that requires a lot of work and must be repeated in order to maintain the desired shape.
When to Prune
You should cut back a fruitless mulberry within the first three years of its life to begin training it in this formal shape. The pollarding method follows the same pruning schedule as other pruning methods. The best time to pollard fruitless mulberries is in late fall or early winter when the deciduous tree is dormant because the cuts are less shocking to the trees. Fall pollarding also helps to ensure full growth during the active growing stage in spring and summer. In some climates, you can also pollard a tree early in late winter or very early spring before leaf buds form. Pruning after leaf buds form seriously restricts plant growth.
Use of the pollarding method traces back to medieval Europe and was basically started by accident. Members of the peasant class were granted permission to cut foliage and new branches from trees for use as firewood, animal feed and building material. When only the new foliage and branches were harvested, it was discovered that the trees maintained their shape and health, and continued to grow new branches each spring.
- University of California Cooperative Extension: Fruitless Mulberry Tree
- University of Florida Department of Horticulture: Morus alba Fruitless Cultivars
- Learn 2 Grow: Pollarding Deciduous Trees
- University of California--Berkeley: 'Pollarding' Trains Trees in Surrealist School
- University of Maryland Cooperative Extension: Pruning Ornamental Plants