Q: My 15-year-old mulberry tree provides wonderful summer shade, but it’s growing up into the power lines, and my neighbor says its roots are damaging his underground sprinkler system. Can I prune the roots to keep them out of his yard? Should I replace the tree? - Sandra Todd, Los Gatos, Calif.
A: Garden diplomacy between neighbors is always delicate. And in this case, responsibility for solving the problem rests with both sides. Your mulberry’s roots didn’t cause the problem - at least, not at the very start. It’s physically impossible for roots to break into pipes or to drill through them to get at water, but they will follow leaking water to its source, and then squeeze through even the tiniest existing hole or fissure. Somewhere, somehow, your neighbor’s sprinkler system must have sprung a leak, luring mulberry roots next door for a drink. Don’t bother trying to cut back the roots or digging a trench for a concrete or plastic root barrier. Wherever the water is, those roots will find it, even diving under barriers as deep as 4 feet. First, the sprinkler pipes should be fixed - they are wasting water.
The sad news for you is that the mulberry tree probably ought to go. Many people plant mulberries because they grow quickly; they can also quickly grow too tall (30 to 50 feet in only 10 to 20 years). I’d replace your mulberry with a smaller tree, which will not spread its roots as far and won’t need a periodic buzz cut from the power lineman, either. Since the canopy of your replacement tree will cover less ground, plant it a little closer to the spot where you need summertime shade. Following are some appealing alternative trees. All drop their leaves in winter, like the ulberry. They will take many years to reach a height of 25 feet and can be maintained at that height or lower with moderate pruning.
For exotic bloom you can’t beat a chitalpa, a cross between the eastern catalpa and a desert cousin, chilopsis. This hybrid tree flowers over a long period in early summer, producing abundant orchidlike blossoms. Crab apples thrive in your region, and many varieties make a wonderful small but spreading tree to sit under. Ask a local nursery for a crab apple with fruit that persists into the winter. You probably think of crape myrtle as a large shrub, but it’s easy to train into a small, multistemmed tree. The best are modern varieties developed for disease-resistant foliage: ‘Sioux,’ ‘Comanche’, and others named for Native American tribes. Flowers range from purple through a wide range of reds to white. In the winter, crape myrtles display lovely peeling bark. Japanese persimmon trees are most glorious in the fall and early winter, when the leaves turn golden and the branches bear avocado-size fruit the color of pumpkins.
Mulberry roots that search for air, nutrients and water are referred to as lateral, or horizontal, roots. This deciduous tree grows an extensive root structure that spreads horizontally from the trunk and remains in the first 24 inches of soil. Along with the wide horizontal roots, mulberry trees also grow smaller sinker roots off the laterals. These important roots typically grow vertically, so your tree has better stability in the soil to support the heavy trunk and canopy. Because most of the nutrients are near the surface, the lateral roots need to remain undisturbed for healthy tree growth.
A typical mulberry tree grows taller than 30 feet and often has an equal canopy spread. The horizontal root structure commonly reaches to the drip line, or canopy's edge, and beyond, for healthy nutrient uptake. Your watering strategy for your mulberry should not be limited to the trunk's base. In fact, roots naturally look for moisture at the drip line because rainfall drips off of the foliage and onto the ground at this point. Watering at the drip line, as well as several feet past this point, helps your tree grow taller and with stronger roots.
There is specific equipment you must keep at hand’s distance before you plan to kill mulberry tree:
These mulberries are native to China and prefer a warm climate. The coldest regions they can be grown in is USDA hardiness zone 6 any lower and the tree would not survive the winter. Black mulberry trees are the smallest of all the mulberry trees, with the ability to grow up to 30 feet in height. However, unless they are pruned when young and trained to form a tree shape, they will often grow into more of a mulberry bush than a tree.
Bears a large black juicy fruit over an inch in length.
This cultivar fruits heavily, bearing an abundance of very sweet fruit of up to 1.5 inches long. The tree originated in LA, USA, in 1971.
This cultivar has interesting foliage, with oversized heart shaped leaves. It enjoys warmth and is an ideal mulberry tree for growing in the southern United States. It originates from Florida and bears large black fruits.
White mulberry trees were originally imported from China to the US as part of the emerging silk trade because silkworms liked to eat mulberry trees. The silk trade failed to take off in North America, but the white mulberry trees were here to stay. They grow easily, being forgiven of poor soil conditions and can also adapt to grow in partial shade. Despite their name, the fruits of the white mulberry tree are actually dark purple in color, though they start out as white. White mulberry trees are the tallest of the three varieties, growing up to 80 feet in height. They can take many forms, depending on the cultivar, with some trees having a weeping habit, while other grow to form a pyramid shape.
The purple fruits of this cultivar are fleshy, juicy, and sweet. The tree originates from California and has a long harvest period of April through to June.
Red mulberry trees, which are also known as American mulberry trees, are native to the United States. They are first known to have grown all along the Gulf Coast up to Massachusetts. Red mulberry trees have a lifespan of up to 75 years and can grow to heights of 70 feet in rich, fertile soil. They are cold-hardy to temperatures below 0 but do prefer warmth. The appearance of the red mulberry is similar to the black mulberry, though it has more delicate twigs and smaller buds. Many red mulberry trees have been hybridized with white mulberry trees to form new cultivars.
Originating in Pakistan, this cultivar prefers warm weather but can tolerate colder winters. It bears exceptionally large fruit, measuring up to 3.5 inches in length.
This cultivar originated in China but has been grown in Europe for over 1,500 years. It is very tolerant of wind, and so, is commonly used as a windbreak. It grows to 35 feet in height and is one of the hardiest cultivars (California Rare Fruit Growers).
Everbearing mulberry trees are vigorous and low-maintenance, able to adapt to a variety of soil types.
These trees thrive with six hours of direct, unfiltered sunlight per day or partial shade.
Everbearing mulberry trees prefer well-draining, moist, loamy soil with a pH between 5.5-7. However, they can also grow in sandy and clay soil.
Newly planted everbearing mulberry trees need to be watered regularly to establish a strong root system. Once established, mulberry trees are relatively drought-tolerant. They benefit from about one inch of water per week.
Everbearing mulberry trees should not be fertilized the first year of planting. Once they are established, fertilize in early spring when new growth begins every year, using a slow-release, balanced fertilizer with an NPK value of 10-10-10.
Pruning your everbearing mulberry tree can lead to a robust branch framework. Only prune in winter, when the tree is dormant. Everbearing mulberry trees are prone to “bleeding,” or leaking sap. You don’t want to prune until the tree has fully stopped sap production in winter.
Everbearing mulberry trees are self-fertile, so you only need one to yield a crop. In general, it can take up to two to three years for everbearing mulberry trees to fruit. However, some nurseries carry everbearing mulberry trees that will fruit the first year. The trees bear fruit from June until September.
Everbearing mulberry fruits don’t even need to be picked— if you shake the tree lightly, they simply drop to the ground when they’re ripe. Many people leave a sheet beneath their tree during these months to collect the berries as they fall.
The fruit is excellent for snacking, baking into tarts or pies, creating jams and preserves, or even fermenting sweet wine.
If planted and attended to with some affection, the red mulberry tree is a beautiful, large, stately species that can produce a bountiful harvest of berries.
Site selection will be an important aspect of the mulberry’s success. It is a large tree in height and spread. Consider a spot that will not just fit the tree now but 15 years in the future. Think about how the tree will interact with the infrastructure and hardscaping. The red mulberry’s messiness makes this step especially important to avoid staining and property damage from falling fruit.
When ready to plant, place the tree in a hole as deep as the container or ball and burlap and two times the width. Mulch around the newly planted tree out to the dripline, ensuring not to touch the bark, helping the newly planted tree retain moisture.
The tree will be its showiest and produce the most fruit when placed in full sun. It does tolerate part shade somewhat well but will not produce as proficiently.
To ensure success, place the red mulberry tree in well-draining conditions that are moist and rich. A loamy soil that is neutral to alkaline is preferred.
Other than when first planted, there is no need to worry about supplemental watering. Initially, it is necessary to water the newly planted tree weekly. A thorough soaking is adequate. A good rule to go by is ten gallons of water for each inch of the trunk diameter. Weekly watering only needs to be maintained for the first year until roots are established.
The red mulberry tree is drought-resistant, but it would be best if you still watered them to keep the soil around them from drying out during a drought. That way good fruit production will be more likely.
The species is a hardy tree with a range covering most of the United States east of the great plains. The red mulberry does well at a variety of temperatures. Its USDA Hardiness Zones are 3-8.
There is no need to fertilize the red mulberry tree. It will do well in most soils, but increasing the yield of berries can be achieved by applying a 10-10-10 slow-release fertilizer every spring.
Broussonetia papyrifera (L.) L’Her. ex Vent.
Mulberry family (Moraceae)
Paper mulberry was introduced for use as a fast-growing shade tree. Native Pacific cultures use it to make bark cloth.
Distribution and Habitat
Found from Illinois to Massachusetts, south to Florida and west to Texas, paper mulberry invades open habitats such as forest and field edges. Internationally, it is identified as an invasive weed in over a dozen countries.
Once established it grows vigorously, displacing native plants through competition and shading. If left unmanaged, paper mulberry can dominate a site. Its shallow root system makes it susceptible to blowing over during high winds, posing a hazard to people and causing slope erosion and further degradation of an area.
Amy Richard, UFL
Prevention and Control
See Control Options.
Basswood (Tilia heterophylla) and sassafras (Sassafras albidum) have similar foliage and form and grow in similar places as paper mulberry.