Mulberry trees can make an excellent addition to a garden with their dense foliage and attractive large green leaves. They are a good shade tree and have the added advantage of producing berries, which are often edible. Mulberry trees require little care, but pruning is important to keep the tree in good shape. In this article, we will be looking at how to prune a mulberry tree without damaging its health.
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How To Prune Mulberry Trees?
We used to have a mulberry tree in the middle of a large paved area in our yard. It was perfect on hot summer days, as it provided plenty of welcome shade. The tree had been pollarded before we owned the property, so we continued with the practice to maintain the tree’s size and shape.
I would, however, suggest that pollarding is a rather harsh step to take, and a hard pruning is better if you want to maintain the tree’s long-term health.
Mulberry trees are quite able to take a severe haircut if it is done at the right time of year. In fact, if you plant your mulberry when it is just a young sapling, it’s possible to maintain it at the level of a shrub.
Tools and Equipment
You may require the following tools and equipment to effectively prune your mulberry trees, depending on their age and size.
- Hand pruners
- Loppers
- Pruning saw
- Chainsaw
- Disinfectants such as hydrogen peroxide or alcohol
- Clean rags to disinfect tools
- Sharpening stone to sharpen blades
Shrub Pruning
To maintain your mulberry as a shrub, it must still be very young. You need to cut the central leader (trunk) back to between 4 ½ to 5 ½ feet in height.
The cut should be made directly above some strong side branches. These branches provide the framework for the shrub, and ideally, you want around eight to ten growing at a wide, open angle away from the main leader.
You’re looking to create an open V-shaped bush.
Additional pruning will need to be carried out annually to ensure the shrub maintains a good height and shape.
Basic Mulberry Tree Pruning Technique
During pruning, mulberry trees often bleed sap where the cuts are made. Even if you prune the tree while it is dormant some bleeding may still occur. Any cuts that are more than a few inches in size won’t heal quickly because the bleeding keeps the wound open. This means disease and pests can enter the tree.
If you have to take off larger branches, seal the cut with a pruning sealer. This acts like a plaster to prevent disease and pests from entering the tree through the open wound. It can be found at garden stores or online.
After the tree has grown beyond the sapling stage, try to avoid cutting the larger main branches. The overall shape should ideally be set when the tree is young.
Branches that have grown too long, need trimming back to a better length. Take out the majority of small branches that are growing into the center of the tree. This allows more light in and lets fruits ripen, and enables you to access the center of the tree more easily to harvest.
At the very least, when pruning your mulberry tree, you want to remove all the dead and diseased branches.
Next, take a look at the overall shape of the tree and remove any branches that cross or touch each other or that are growing directly up or directly down.
- Sterilize all cutting tools using hydrogen peroxide or alcohol.
- Remove dead or diseased wood. Ensuring you clean tools regularly to prevent disease spread.
- Look at the overall shape and remove branches that spoil the appearance of the tree.
- Remove the small branches from the center of the tree to encourage an open cup shape.
- Remove the ends of the branches to reduce the height and spread.
In this video, you will see the technique of pruning mulberry trees for fruiting:
Why You Should Avoid Pollarding?
As I mentioned earlier, some people like to pollard their mulberry trees. Pollarding is where all new growth is cut off, back to the main branch. This forms branches that look like clubs.
Although pollarding keeps the size of the tree in check, there are several reasons why this isn’t a good idea.
Fruit is produced on new growth and particularly from buds that are a year old, by removing all new growth, you’ll get almost no fruit.
Pollarding also weakens the tree and will reduce its lifespan. Pollarded trees tend to suffer more from disease than un-pollarded ones.
Pollarding is often practiced on mulberry trees grown on sidewalks, because the juice of the fruit is very messy and stains, so is not wanted.
When To Prune Mulberry Trees?
Mulberry trees should be pruned in winter while the tree is dormant. During this time, the tree won’t be actively growing, and the branches will have no leaves. This makes it easy to see the form of the tree and access all of the branches.
Pruning should be avoided during the spring and summer months because you can’t see the skeletal form of the tree, branches are harder to access, and more pruning damage is done to active wood, due to excessive bleeding that stops wounds from healing.
Open wounds may allow pathogens and pests to infect the tree.
How To Prune A Weeping Mulberry Tree?
Weeping mulberry trees are an attractive form of mulberry. It has branches that cascade downwards towards the ground rather than up towards the sky.
The weeping mulberry is a very vigorous growing tree that is essential to silkworms for food and habitat. Like other mulberry trees, they are deciduous and lose their leaves during the winter months.
As with the standard form mulberry trees, the weeping form also makes an excellent shade tree and will produce fruit.
Pruning Technique for Weeping Mulberry
When pruning your weeping mulberry, always make the cuts just above new buds. Ensure the cuts you make are clean, leaving no splintered wood.
- Just as when pruning any kind of tree, keeping your cutting tools sharp and clean is essential to prevent introducing or spreading disease.
- Wipe your cutting blades with hydrogen peroxide or alcohol.
- Start by removing all the dead or diseased branches. Re-sterilizing tools as you go.
- Stand back and assess any branches that are not growing in a pleasing way and give the tree an odd shape. Prune these off.
- Open up the tree by removing any branches that are touching or crossing others. You want the form of the tree to be like an umbrella so that there is good air circulation and the sun can get into the middle.
- Cut off branches with a V-shaped union. The place where the branches meet can cause weakness. Instead, you want to encourage U-shaped unions where the limbs come together as this produces stronger, thicker branches.
- Remove the tips of the branches, cutting them back to about a foot of where you pruned to the previous year.
Pruning will help strengthen your tree by increasing healthy growth and forming more substantial limbs.
Weeping mulberry can be prone to storm damage, and pruning can help the tree to become more resistant to this.
How To Prune A Fruitless Mulberry Tree?
Just like other types of mulberry trees, fruitless ones should also be cut during the winter while the tree is dormant and has no leaves.
Fruitless mulberry trees are fruitless because they are male specimens or because they are pruned back hard each year or every other year to prevent as much of the year-old fruiting wood from growing and producing fruit as possible.
Often you will find that a fruitless mulberry tree is pollarded, and the branches have formed a club-like knuckle on the ends.
New branches grow from this knuckle each year, and it is these branches you need to cut back, down to the knuckle in the wintertime, leaving just a couple of inches of growth.
Although this is common practice, it isn’t beneficial for the tree’s health. It is done mainly to keep the size of the tree small and limit fruit production. Pollarding is popular in many parts of Europe.
Mulberry Tree Pests and Diseases
There are a variety of pests and diseases that affect mulberry trees. We will take a look at some of the most common ones here.
Bacterial Blight
- Recognition – Leaves develop water-soaked spots before they wilt and die. The shoots start developing black stripes before drying up and wilting.
- Treatment – Prune all dead shoots during autumn. Use a fungicidal spray in autumn and spring, before leaves start to develop.
Canker
- Recognition – Areas of bark start to peel, and the tree may weep fluid. Twigs and branches die off. Old canker can be recognized by the development of thickened areas on the trunk or branches.
- Treatment – There are various types of fungus that cause cankers, and it is often due to trees becoming stressed. Remove all dead branches and burn them. Ensure that trees are kept healthy and provide water and fertilizer.
Cotton Root Rot
- Recognition – Another fungus prevalent in white mulberry trees. It is called Phymatotrichum omnivorum, and it causes cotton root rot. Texas and Oklahoma have the most instances of cotton root rot.
Symptoms typically appear from June to September and start by looking like water stress. The leaves all die beginning at the top of the tree. They don’t fall off, however. Roots will appear decayed with a covering of tan-colored, fuzzy mold.
- Treatment – By the time cotton root rot is identified, it is almost always too late to save the tree. The only thing which may work is cutting it back severely and watering heavily.
Prevention is better than cure, and this can be done by:
- Treating the soil with Ammonium Sulfate, Sulfur, and Manure
- Adding lots of organic matter to the soil around the tree
- Using a Moldboard Plow to prevent the spread of the fungus through the soil
False Mildew
- Recognition – This fungus often attacks Mulberry trees growing in the southern states. Whitish patches begin to appear on the underside of leaves in July.
This is followed by the emergence of yellowish spores and a white cobwebby coating. It has an appearance not dissimilar to mildew, hence the name.
- Treatment – Infected leaves fall to the ground in fall, where the spores lie dormant until springtime when they mature and reinfect the tree. To break this cycle, rake up and burn all leaves in the fall. Spay infected leaves with a fungicide in July.
Leaf Spot
- Recognition – This is more common in wet areas or in years with higher than usual rainfall. Leaves of the mulberry tree develop spots caused by a fungus.
- Treatment – Spray leaves with an approved fungicide.
Mushroom or Armillaria Root Rot
- Recognition – As the name describes, this is a colony of large fungi (mushrooms) that attack the roots of the tree. The spores are often present on healthy rootstock and only invade when the roots become damaged in some way.
- Treatment – It is only possible to save trees that are lightly infected. For severe infections, the tree should be removed and the soil treated before any replacement is planted.
Carefully remove the soil from the tree’s base and for a one-foot radius. To prevent further damage use a high-pressure water jet to do this.
Cut out any diseased roots and bark and burn them. Paint the cut areas with a pruning sealer or plastic paint.
Don’t replace the soil around the tree’s base, as air exposure will kill the fungus.
Powdery Mildew
- Recognition – Caused by a fungus, powdery mildew affects the lower surface of the leaves by covering them with a powdery white coating. This will eventually kill the leaves.
- Treatment – The application of an approved fungicide can be used to treat the infection. High humidity often makes this fungus more problematic.
Root-Knot Nematodes
- Recognition – These are parasitic, microscopic nematodes that are more commonly found in places with long hot summers and short winters. The larvae infect the roots of the tree and drain it of nutrients.
This causes small bulbous growths (galls) on the roots and can be lethal to young trees. It is seldom problematic to older ones. Trees lack vigorous growth, leaves are smaller and there is often a dieback of twigs and branches. Fruit yields are low, and there may be other diseases present such as cankers and bud blight.
- Treatment – There is no actual treatment for this problem. Soil can be cleansed of nematodes prior to planting trees, but this is a long and complex task.
Mealy Bug
- Recognition – This hard-to-kill pest can be found in regions with a hot, moist climate. The insects cause damage to mulberry trees year-round but are generally worse in July and August. The bugs feed on leaf sap and you will find them under the leaves and at the joints of stems.
The leaves become wrinkled and thickened. At first, they turn dark green and then turn yellowish. A black, sooty mold sometimes develops on leaves and stems with a heavy infestation.
Treatment – Cut off infected leaves, shoots, and branches, and burn them. Fish oil or Rosin soap can also be sprayed on the affected leaves. Beetles that eat the bugs, such as Cryptolaemus montrouzieri or Scymnus coccivora can be used to control the infestation.
Spiraling Whitefly
Recognition – Native to Central America, these pests like hotter, more humid climates. Whiteflies feed on plant nutrients causing the leaves to become shredded.
They leave vast amounts of honeydew that produces a sooty mold on leaves. Plants become disfigured and, with high enough populations, can die. Leaves curl and yellow. They leave a white spiral pattern on leaves when laying eggs which is how they get their name.
Treatment – This whitefly can build up resistance to chemical pesticides rendering them useless. A good remedy is Neem oil which can be used to spray on affected leaves.
Thrips
- Recognition – Also known as thunder flies or storm flies, thrips can damage young mulberry leaves. They start by showing discolored streaks, and later blotches. The quality and quantity of mulberry leaves will be affected in the subsequent year. Nymphs suck sap from leaf cells which dries the leaves out.
- Treatment – Thrips like dry conditions and can often be significantly reduced by using a sprinkler system that periodically sprinkles the underside of the leaves with water. Frequent irrigation reduces numbers on leaves and increases pupal mortality in soil. Approved insecticides may also be deployed.
Conclusion
As with many other fruit trees, keeping your mulberry trees correctly pruned can increase not only their health but also the amount of fruit it produces.
For ornamental mulberry trees, harsher pruning can be more advantageous, as mulberry has a very high growth rate and can put on several feet of new growth in just a few months over summer.
The general rules are:
- Sterilize tools and keep them clean and sharp
- Remove all dead and diseased wood
- Remove any branches that are spoiling the look of the tree
- Cut out all small branches at the center of the tree
- Prune away any branches that cross or are touching
To read more articles on mulberry trees and their care, please visit our blog.
