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Growing Mulberry Trees


A mulberry is a sweet, edible fruit produced by a mulberry tree (Morus). Mulberry trees are grown worldwide and have been cultivated by humans for thousands of years. There are several varieties of mulberry trees, so it is important to choose one that is right for your area.




Choosing a Variety


Size


Grafted mulberry trees are all similar sizes that can be maintained as small as 6' feet, but will grow unpruned to approximately  25' to 30' tall.


Size


Grafted mulberry trees are all similar sizes that can be maintained as small as 6' feet, but will grow unpruned to approximately  25' to 30' tall.


Size


Grafted mulberry trees are all similar sizes that can be maintained as small as 6' feet, but will grow unpruned to approximately  25' to 30' tall.





Pollination


Mulberry trees are self-fertile and require no pollinator, however a pollination partner will increase the size and quality of the harvest.

Pollination is important during your orchard planning as well. Since mulberries are wind pollinated they will still produce fruit even in conditions where local pollinator insects are not present. The pollinizer trees should be planted no further than 50 feet apart, to ensure proper cross-pollination.





USDA Plant Hardiness Zone


Mulberry trees are hardy to USDA zones 4-8, unless otherwise noted. This rating tells you the minimum winter temperature the plants typically survive when properly hardened off. Make sure you consult the USDA Hardiness Maps website, which provides information on the average minimum winter temperature in your location, by zip code. Your USDA Plant Hardiness Zone does not reflect the many of the other factors in successfully growing apple trees, including length of growing season, rainfall amounts, soil quality, and chill hours. Consult your local extension service for more detailed information about your local growing region and the factors you will need to know when selecting fruit trees for your home orchard.





Chill Hours


All plants have what are called a "chilling hour requirement" in order to flower and produce fruit. Chilling hours are defined as the cumulative period of time between 45 and 32 degrees Fahrenheit and vary from region to region. The majority of apple trees have a chilling hour requirement of anywhere from 500-1000 hours, with some requiring more and a few requiring as little as 200-300 chill hours to blossom and produce. Fruit trees that require less than 600 chilling hours are considered "low chill" and are generally more resistant to more intense summer conditions than apples trees with higher chilling hour requirements. The general chilling hours available for you specific location can be found online or determined by your local extension office.





Where to Plant your Plant


Mulberries need to be planted where they receive at least 6-8 hours of direct sunlight measured in early summer (late June to early August). Sufficient sun exposure triggers the initiation of new flower buds for the next growing season, without which there will be no fruit. Fruit ripening and flavor development are also benefited by the carbohydrate production stimulated by the sun, as well as it’s heat.

Mulberry trees tolerate a wide variety of soils so long as they are well drained and moderately rich with a pH around 6.3-6.8. Improve your soil where you intend to plant by mixing an inch or two of plant based organic matter(manures are best for vegetable gardens), peat, or coconut coir into an area 1 1/2 to 2 times the diameter of the needed planting hole and up to a foot deep. A 2-4” deep layer of mulch (straw, leaves, or wood chips)applied after planting will continue to improve the soil.

Allow sufficient space for both the top of the tree and it’s roots when selecting the planting location. Do not plant mulberry trees near water lines or septic fields. Mulberry trees are water loving and will aggressively seek water and may damage pipes and septic lines. Refer to size descriptions for each variety, keeping in mind these are generally managed or pruned sizes, not maximum potential sizes. If you are planting an orchard be sure to include enough space between rows for transporting supplies in and fruit out.





Growing in Containers


Mulberry trees generally grow too large to successfully grow in a container for more than a few years. Gerardi dwarf mulberries can be grown in a large container, but due to their water needs container plantings my require daily irrigation and regular pruning to stay happy and healthy.

Do not use soil from your garden to the pot, instead use a potting soil mix with some added compost. For larger pots use a potting mix that has a larger particles in addition to smaller ones.





Care and Maintenance


Watering Your Plants


This is the most important and often the most difficult part of successfully growing plants. There are many factors, including the humidity, temperature, soil type, wind, and amount of direct sun that affect how much and how often water should be applied.

A general rule of thumb for plants in the ground is to ensure they receive an inch of water per week over the root zone. An inch of water is equivalent to about ¾ to one gallon per square foot of soil surface area. The typical three foot diameter planting hole would need 7 ½ to 10 gallons of water per week provided by rainfall or by the gardener. Mulberries are especially water loving and may require more water, more frequently, to become established as quickly as other fruit trees.

Apply this water once a week, two times per week if soil is fast draining. This will of course depend on your own conditions and the plants you are growing! DO NOT water lightly each day because this results in a wet surface and dry root zone area. The soil should be moist but not soggy to a depth of about a foot for most growing plants. The top inch or two can feel dry, and the plant still be well watered. The trick is to have the water available where the roots are. In hotter and sunnier areas, a mulch of straw, bark, etc. can greatly ease the burden of summer watering. For plants in containers, water until the soil is saturated and water comes out of the drainage holes. Let the container dry until the soil is dry to the touch 1 to 2 inches down (more deep with deeper pots) and the container is lighter in weight. A plant that has wilted can be receiving either too much or too little water.

In rainy areas like the Pacific Northwest most of the plants that we offer will need relatively little supplemental irrigation ONCE THEY ARE WELL ESTABLISHED in the ground and have had a chance to develop a good root system. However even here it is important to make sure plants have regular, deep watering during the first couple of growing seasons, and the first summer is especially critical. In drier areas, or where soils do not retain water well, permanent irrigation is essential. Remember that you don’t want your trees to just survive, but rather to thrive. Make sure they get the water where they need it, starting at the drip line and extending away from the tree up to several feet ( for older trees) where the feeder roots will be. Drip irrigation and soaker hoses can be an efficient way to deliver the water.


Fertilization


For good steady growth and high productivity, your trees need to have adequate amounts of various mineral nutrients. Some people are fortunate and have naturally rich fertile soil.

Use an all-purpose or balanced fertilizer. A couple of inches of well-rotted compost on the root zone can also be an effective fertilizer. A generous leaf or straw mulch around your trees will not only conserve moisture and help in weed control, but also keeps your soil healthy by building up humus,attracting earthworms, and supporting beneficial fungal organisms. This encourages young trees to be strong, healthy and productive. Avoid applying fertilizer after early summer, doing so can encourage lots of soft new growth that is much more likely to be damaged by winter cold.Excessive use of fertilizer can in-crease disease problems on your plants and can even kill them.

As a general guide, if your tree is producing about one foot of new growth or more a year and has healthy looking foliage, it may not need much or any fertilizer.




Pest and Diseases


Find out what insects and diseases are typical in your area. Ask your local co-operative extension professional what the typical insect and disease issues are in your area. Then you can make selections based on resistance or tolerance information available in our catalog, or, make a plan for controlling problems you can expect with the susceptible varieties you prefer to grow. If you see resistance information about a particular disease for one variety but not another of the same kind of fruit, then that variety may be susceptible or might not have been tested so is unknown. The following are some of the more common issues.

Popcorn Disease


Symptoms

Fungal disease caused by (Cibroia carunculoides) that manifests on the developing carpels and looks like popcorn kernels. Occurs in late spring and early summer. Primarily cosmetic and does not harm the tree, but does ruin the fruit.

Control Methods

Sanitation. Clean up any infected material and remove it from the area where the tree is growing.  Spraying the tree with Bordeaux mixture may help too.

Comments

Primarily cosmetic disease that does not hard the tree, but does destroy a portion of the fruit. Serious concern for commercial operations, less so for home growers.


Cercospora Leaf Spot


Symptoms

Mulberry trees are susceptible to two cercospora fungi: (C. moricola) and (C. mori). Leaf spot infections cause reddish-brown spots on the mulberry tree’s leaves. The spots are may be round or irregular and vary in size. Some have a purplish outer margin, like a halo. Fungus spreads via splashing water and is most active during rainy weather or when the mulberry’s foliage is watered.

Control Methods

Prune out the infection and dispose. Do not compost the plant debris; burn the material to destroy the fungal spores. Fungicides are effective at preventing leaf spot on mulberry trees. Spray needs to be applied in early spring, right at bud break, and repeated at 10- to 14-day intervals.

Comments

Keep the area beneath the tree free of weeds, turf grass and plant debris to eliminate hiding spots for cercospora spores. Water the tree only from the bottom, or water early enough in the day to allow the foliage to dry completely before nightfall. If severely infected and treatment not working consider replacing tree.


Fusarism Canker


Symptoms

Elongated lesions in the bark of branches or main trunk of the mulberry plant. The canker disrupts the flow of nutrients, resulting in die-back of the branch above the canker.

Control Methods

Cultural control. Cut branch at least 3" below the infection. Dispose of infected wood by burning. No effective chemical controls.

Comments

Cutting through the branch at the site of the lesion will reveal dark discoloration in the wood.


Deer


Symptoms

Browsed shortened branches. Leaves are obviously munched on or plants are pulled up.

Control Methods

Fences or cages at least 8’ tall. Plastic mesh, electric, or woven wire fences.

Comments

At Raintree, an 8’ woven wire deer fence has worked best. Repellents don’t work consistently and, aside from fencing, only trained large dogs patrolling the perimeter are effective.


Bird


Symptoms

Fruits disappear or have gaping holes in them. Strawberries, blueberries, cherries and filberts are most susceptible but most fruits suffer occasionally.

Control Methods

Reflective Bird Scare Tape can work well. Bird netting. Cages.

Comments

Blue Jays start harvesting filberts when ready to pick, and so should you. Nuts dropped by jays are usually empty.


Vole/Mouse/Rabbit


Symptoms

Bark eaten in a band from soil level up to 8” and roots eaten too, usually in snowy areas with lots of mulch or tall grass at base of trees.

Control Methods

Keep mulch 4”-6” away from trunk. Keep grass short and 1’-2’ from trunk. Use vinyl tree guard wrapped around trunk until tree well-established.

Comments

Voles and mice will chew a couple inches above ground and also into the root system. Rabbits will chew up to 8” high, particularly apple trees.


Spotted Wing Drosophila


Symptoms

Eggs are deposited 7-10 days prior to fruit ripening; holes in fruit, spotty molding, larvae in fruit, exuding berry sap, scarring.

Control Methods

Monitor with traps. Spinosad. Sanitation: In fall, adults feed on overripe or split fruit (both vegetable and tree fruit) to prepare forwinter.

Comments

Contact your local extension office for the most up to date information on spotting wing drosophila.


Brown Marmorated Stink Bug


Symptoms

Poking-type feeding damage followed by decay on fruits, nuts, berries and leaves. Deformity in the healthy tissue surrounding the dead tissue. Brown spots can show up in stored fruit.

Control Methods

Monitor with traps, some broad spectrum pesticides may work. Researchers are working on finding effective controls, but no info has been released yet.

Comments

BMSB over winters in groups in dry protected areas, such as houses. If you find them on or in your home use the vacuum, squishing releases their defensive stink.  See stopbmsb.org for more info. Feeding begins in spring when the weather warms up and continues until new adults go dormant for winter.