Pruning and Forming Chestnut Trees

Chestnut trees naturally will grow 18 to 48 inches or more in a year as long as the growing conditions permit. The trees will continue to grow until they reach their genetically determined height. Some types of chestnut trees can reach a height of up to 80 feet. Some types of chestnut trees reach their maximum height of 40 feet and then only grow out depending on available space. Chestnut trees, like many other fruiting trees, can be kept much lower than their natural height through annual pruning. Also, like other fruiting trees, chestnut trees will produce more nuts per tree or per acre if the trees are pruned in ways that maximize nut production.

Why even consider pruning a chestnut tree, they seem to grow just fine without bothering them? There are many reasons to prune trees. The most important reason is to keep the tree healthy. Removing broken or damaged branches, diseased sections, and keeping a balanced tree are all important reasons to prune chestnut trees. If you are a commercial chestnut producer, pruning the chestnut trees in your orchard will help achieve the highest production. These are just a few of the motivating factors that brings us to the point where pruning trees is the best option.

When considering when to prune an orchardist has two times in the annual growth cycle of the tree, winter and summer pruning. Most of the pruning occurs in the winter on try days. It is during the winter pruning the shape and height of the tree is addressed. During the summer pruning only the growth that is unwanted is removed as well as any diseased portions of the tree. If any branches break during the growing season these should be removed as soon as possible. Do not wait for the winter pruning for their removal.

Pruning during or shortly before rain (2-3 days) can provide a path for disease to enter the tree. Water dripping into the open new cuts is the most common path of infection. Chestnut trees for the most part do not bleed. Without the bleeding, new cuts are left vulnerable until the exposed area is healed.

Pruning and Training Tools

Before setting out in to the orchard to start pruning you will need some tools. High quality pruning tools save time, labor, and make the cleanest cuts that heal the fastest. Also, always keep cutting edges as sharp as possible. Here is as short list of the tools you will need.

1. Orchard ladder
2. Pruners (Felco #2)
3. Pruning saw (Felco 600 - 6 inch folding)
4. Bypass loppers (Felco 22)
5. Sawzall - cordless with pruning blade
6. Chainsaw - gas powered

Knowing which tools to use for the job at hand is almost an art form. A few guidelines are helpful, so here are a few:

- If the tool your are using is not working very well, causing you to exert to much effort the tool might be to small for the job.

- If the tools is oversized for the job then it will be difficult to properly place the cut or the tree might get damaged.

- Pruners should be used for cutting branches from 0 to 1-1/2 inches.

- Loppers should be used for cutting branches from 1 to 2-1/2 inches.

- Pruning and sawzall saws should be used for cuts from 2 inches to 4 inches.

- Cuts larger than 4 inches should be done with a chainsaw.

- Never operate a chainsaw above the shoulder height.

- Never stand on or above the top two steps on a ladder.

- If working above 6 feet off the ground it would be wise to wear a harness and be tied off to the tree you are working on.

Sharp tools can be your best friend by helping to make pruning a manageable task. Tools can also inflict permanent body damage or even death. The best way to keep from hurting yourself or others is to only use a tool in the way they were designed for. Also, keep some first aid supplies such as band-aids, 4x4 gause dressing pads, and a roll of 1 inch first aid tape in your pruning bag.

Before cutting on trees there are a few more rules to keep in mind:

1. Never remove more than 1/3 of the tree in any one year

2. Unwanted growth should be removed as soon as it is noticed (this is the summer pruning). When unwanted growth is allowed to continue the trees energies are wasted.

3. Chestnut trees produce short little branches that only grow a few inches long. Never remove these branches because they seem to function as a place for the chestnut tree to store energies. These small little branches will die and fall off after a year or two.

4. Chestnut trees do not produce nuts on shaded branches.

5. When cutting branches, leave the sholder at the intersection of the branches.

Pruning and Training, what's the Diff

Pruning is the traditional method of maintaining the tree structure. The more recent development of training trees focuses on the growth and directs the tree to the desired shape and form. Winter pruning or dormant pruning of chestnut trees is done in the dead of winter (late Dec through late Feb). Since the tree stores its reserved energies in the main trunk and roots, dormant pruning does not normally effect the vigor of the tree. Summer pruning does effect tree vigor so summer training/pruning should be limited to removing new growth. Summer pruning is performed from the time the tree buds out until the end of July. Any new growth after the first of August will not have time to harden off before winter. From the first of August until the end of December you should not be cutting on chestnut trees except if branches break.

If your chestnut tree is no longer balanced then the changes to the trees structure must be made during the dormant pruning. A balanced tree helps protect the tree from being blown over in high winds. When preparing to rebalance a chestnut tree also consider opening up the tree with fewer inner branches. This does two things for the tree. First, it opens it up to more sunlight helping to keep the tree healthy. The second thing is an open tree has a lower wind profile reducing the chances of the wind blowing down the tree.

Training chestnut trees need to be done if the first 5 years in the orchard. The problem with training a fruiting tree is that it will result in a decrease in fruit production in the formation years. A properly trained chestnut tree will far out produce a chestnut tree just left to grow. One has to wonder if all the additional labor and lower initial production is worth the effort. Studies done at several research stations have demonstrated that training fruiting trees has a excellent return on investment. The math gets complicated when considering the future value of the lost production in the early years. Aside from the actual lost production there is the fruit quality and size issues that come into play. Smaller fruits bring lower prices than larger fruits. There is also possible lost market share and not having a trackable growth in production making sale of the first few large crops difficult. If there was an easy answer to all this it would be well documented in most of the publications about producing chestnuts commercially. Good luch with your chestnut tree forming and training decisions.

Forming the Chestnut Tree Structure

The Australian Growers Resource Manual discusses four tree form systems. The most commonly used system is the central leader system. There are many resources on the web that details how to form a central leader system on trees. One of the best is Fruit Trees: Training and Pruning Deciduous Trees. Another one is from the University of Florida Pruning and Training Deciduous Fruit Trees for the Dooryard. With either of these publications you should be able to get a feel for how to get the central leader system going on a chestnut tree. One major difference between the fruit trees discussed in these publications and chestnut trees is that chestnut trees grow much faster than other fruit trees. With fruiting trees there are dwarfing root stocks. Chestnut trees do not have dwarfing root stocks so the trees will naturally want to grow tall fast (this depends on the chestnut cultivar).

In Europe a chestnut tree form system referred to as the Eurovase system has been developed. This system is also know as open-center is used on peach trees. One of the best publications on the web discussing the open-center tree form is Pruning Peach Trees. This publication is one of the only ones that also discusses fruit loading on the tree structure. Many chestnut tree cultivars suffer from the same fruit loading issues so even if you do not use this form for your chestnut trees you should read this publication anyway. It may save you a lot of broken branches.

The canopy training system is not well documented and little research has been done in the USA for this system. The tree will end up as a very short tree with the scaffolding being formed by only two or three branches. Each branch points in a different direction covering between 120 and 180 degree of the circle forming the tree canopy. There is a trial using this method under way at the Univeristy of Missouri agroforestry research center. The trial is under the guidance of Dr. Hunt. This training system looks promising considering the relationship between sunlight on the canopy and nut production. The chestnut cultivars that may work well with this method might be Chinese based and Japanese based hybrids like Colossal and Qing.

The Y-top forming system is similar to the canopy system in the tree from and the focus on exposure to sunlight. The main difference is the Y-top uses four branches in a two layer scaffolding. Each of the branches covers about 90 degrees. This system may be better suited for chestnut trees because it distributes the load over more branches and provides for a greater vertical area that chestnut trees prefer to naturally grow to. Some chestnut cultivars that might work better with this training method are Precoce Migoule, Okie, and Marival.

Summary of Pruning and Training Chestnut Trees

If your are the type of person who has a tendency to take on too much then consider just letting your chestnut tree grow on their own. They will do just fine as long as you are dependent on all your income coming in the form of chestnut production. Otherwise, put a plan together that includes economic factors, marketing plans, labor, materials, and equipment requirements around how your chestnut orchard will be formed. From all the research available consider "Open is good".