There are three species of mulberries (Morus spp.) commonly grown for their small fruit crops in summertime. Trees are either male or female in gender, with female trees producing the fruit. When grown under full sun and in moist, deep, fertile soils, the trees grow quickly and usually bear copious amounts of fruit that is devoured by songbirds. Pick the fruit when ripe on the tree; ripe fruit coloring varies by mulberry tree species.
Three mulberry species are regarded worldwide as fruit trees. White or silkworm mulberry (Morus alba) is native to China, black mulberry (Morus nigra) is from central and western Asia and the red mulberry (Morus rubra) is native to eastern North America. Among these species hybrids have been developed that are unique and different from their parent stock in several ways.
Plant the appropriate mulberry tree for your climate and soils. Consult the United States Department of Agriculture (USDA) map that classifies areas by the hardiness required for flora to flourish. White mulberry is hardy in zones 4 through 8; both red and black mulberry are best in zones 6 through 9. Only white mulberry tolerates coastal conditions, alkaline soils and extreme heat well.
With varying tolerances, the best growth and production from mulberry trees occurs in soils that are fertile, deep and moist. The soil must be well-draining, with incorporated organic matter, and it best ranges "near neutral" in pH, between 6.0 and 7.8. Avoid gravelly or sandy soils, or any that are shallow, such as those only one to two feet deep over a hard rock layer or coral pan.
As long as soil has sufficient incorporated organic matter or organic mulch lays atop it and under the tree year-round, nutrients are adequate for the mulberry. However, a granular, slow-release, well-balanced fertilizer can be scattered according to product directions in mid-spring on less-than-ideal soils.
Plant mulberry trees in full sun exposure so that they receive at least eight hours of direct rays each day. Inadequate lighting causes irregularly shaped trees, diminished flowering and subsequently reduced chances of fruit formation.
Since trees are fast-growing, prune branches back by 30 percent when the trees are 1 to 2 years old to allow the trunk and branches to strengthen without excessive leafy branches. Often branches are long and drooping, adding weight and stress to branch junctions in winds or when loaded with fruit.
In some regions, mulberry trees are considered weedy or messy trees. They are fast-growing and susceptible to wind damage, and drop lots of fruit and foliage that will coat and stain anything below them . Droppings from birds gorging themselves on the fruit contribute to the problem. These issues that must be considered before growing or planting a tree in a garden or urban landscape. Seeds from fruit eaten by birds are scattered around the landscape and germinate weedy seedlings.
Since mulberries do not ripen further once picked, become familiar with the color of ripe fruit in a given species and harvest them quickly. White mulberry fruits are creamy white and are sweet but somewhat drab and tasteless when ripe. The black mulberry fruit is first red and then becomes dark purple when ripe in late summer, with a sweet acidic flavor. Red mulberry fruit is sweet and ripens to dark purple in late summer.