Growing a Mulberry Tree
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.
Size
Grafted mulberry trees are all similar sizes that can be maintained with pruning at anywhere between 6' and 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 you need pollinators to fly between your mulberry trees. The pollinizers should be planted no further than 50 feet apart, to ensure proper cross-pollination.
USDA Hardiness Zone
Mulberry trees are hardy to USDA zones 4-9, unless otherwise noted. This rating tells you the minimum winter temperature the plants typically survive when properly hardened off. On our web site you will find a USDA Hardiness Maps which provides information on the average minimum winter temperature in your location, by zip code.
Chill Hours
Mulberry trees need a certain number of chill hours per year, which means that you need to pair the chill hours to your climate. If you live in the south or an especially temperate area, you will want to choose a variety of mulberry classified as “low-chill”. This means they have a lower required amount of hours the temperature is below 45F degrees.
Where to Plant Your Tree
Mulberries need to be planted where they receive at least 8 hours of full sunlight. People often don’t realize that it is the sun that ripens the fruit, and without enough of it your fruit will never fully mature.
Mulberry trees like well-drained soil, nothing too wet. Soil can be somewhat rocky and sandy, but needs to be moderately rich and retain moisture as well as air. Clay soil should be amended prior to planting, but can be accomplished by mixing in coco-coir and perlite to improve drainage.
Growing in Containers
Mulberry trees generally grow too large to successfully grow in a container.
Care and Maintenance
Watering Your Tree
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.
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 1-2 inches down 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, 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 they need.
One method is through drip irrigation. We use half- inch flexible plastic pipe with punch-in emitters for trees in the ground. For each young tree, we use two emitters, spaced one foot from the trunk. The pipe can be put on the ground, under the ground with risers, or tied loosely from the trees. We use emitters that drip one gallon per hour. See drawing above. There are many different styles of drip systems, some controlled by timers and others by hand. Or, each tree can be watered with a hose deeply about once a week. Sandy soils will need more frequent watering than clay soils. For smaller plants, like strawberries or raspberries, soaker hoses work very well.
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. Many soils, however, are deficient in some nutrient or another and use of fertilizers, organic or chemical, can be highly beneficial if you want your trees to grow well. If you have a large gardener orchardist can be well worth it to have your soil analyzed by a qualified laboratory so you know for sure just what your soil needs. Typically this might cost $30-$60, depending on how detailed an analysis you want. Unless you know what is available in your soil, you will not be able to supplement it properly.
Use an all-purpose or balanced fertilizer like the organic fruit tree and shrub fertilizer. A couple of inches of well-rotted compost on the root zone can also be ineffective 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. Use of concentrated products like chemical fertilizers or strong organics (for instance blood meal) is usually done from late winter through early summer. Applying fertilizer after early summer 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. Use of too much fertilizer, whether chemical or organic, canals contribute to stream and groundwater pollution, so please try not to use more than your trees really need. 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.