Fruit pruning season nearing its end

WAUSAUKEE — One activity that all home fruit growers need to do every year is pruning. Some years the pruning needs are less, but it should be done every year to help keep your trees, shrubs, and brambles productive and healthy. The optimum timing to conduct fruit pruning is generally late winter and early spring. This year’s weather patterns are creating what is considered a relatively normal fruit pruning season, in that we should plan on being done by about April 15 in the Marinette and Oconto county area.

All fruits are perennial crops and all need various types of management attention over the course of the year. Proper pruning helps keep the plants structurally sound, helps manage fruit load and maintain annual bearing patterns, and plays a huge role in pest management. In reality, there are three primary goals of proper pruning:

1. Structure maintenance (height, width, branch angles, spacing of branches)

2. Creating optimum air flow and light penetration

3. Getting rid of broken, diseased, injured, and dying branches/canes

It is usually a good idea to start with point No. 3 when you are beginning to work on a particular tree, shrub, or bramble patch. By removing any branches or canes that have problems first, you can then actually see what good materials you have to truly work with to achieve the rest of your goals. The danger of starting major pruning without getting rid of these problematic ones first is that you will make improper spacing decisions and end up with larger ‘holes’ in the canopy than you anticipated.

Structure maintenance is a huge part of why we prune and will need to vary according to the natural size of the tree or shrub, or perennial canes such as blackberries. With fruit trees, one key is to select branches that have L-shaped branch unions as much as possible, as these have the strongest connection wood and the ability to produce fruit more quickly and to simply bear more fruit weight. Y-shaped branches should be pruned off as often as possible, as they have very weak branch unions. U-shaped are usually decent strength, but a step down from L-shaped.

If your tree does not have enough branching and you need to keep some weaker branches, consider training them into more of an L-shape by adding weight onto them or attaching the branch to a stake. The point of attachment cannot be wire or rope, however. Use a broad (one inch minimum) piece of material that you can attach via grommets or holes. Only leave training materials on the tree for one growing season, or they can cause damage.

Height and width are dictated by the genetics of the rootstock and the fruiting cultivar, with some variance according to the growing conditions at your site. Most homeowners are best served to select trees at purchase that will meet your space needs, rather than trying to prune trees or shrubs back to a smaller size than the plants want to naturally be. That said, if you are faced with a tree that is too large, you can step the entire tree back, but topping the tree is not the route to go. Topping creates huge hormonal imbalances in the tree or shrub and will cause problems for years. Maintaining a flat or trellised tree is possible in commercial orchards because of the high degree of management that they provide. It is not recommended in the home orchard.

Creating air flow and light penetration means thinning of branches, some larger and some smaller. Start this process by looking for any branches that cross or hit each other, and take the weaker of the two out. Use that same approach to selecting branches for thinning. You want to leave strong branches (L-unions) that are growing in their own zone so that they have full sun and good air flow. Thinning of twigs and small branches is often also necessary, even though you are keeping the main branch. This also helps manage fruit load to have more sustainable fruit capacity year to year.

The same concepts apply to shrubs and raspberry patches. For bush fruits (currants, blueberries, etc..) take out damaged canes, and select at least a couple canes in each size range to keep. The best fruiting canes are usually 8-12 years old, with older canes often decreasing in vigor. However, you want young and intermediate canes of each age class to ensure consistent fruiting and to prevent lack of fruit if something unforeseen happens to the older canes. For raspberries, the key is to take out all old dead canes, as red and yellow raspberry canes only survive one winter. Then, thin out all the weaker or shorter canes. Most raspberry patches have maximum fruit load and quality by having only 4-6 canes per foot of row.

Lastly, try not to go overboard. A good rule of thumb is to take off no more than 10-15% of the living weight of the tree in any one pruning year. In certain cases with older trees, you may need to break this rule in an attempt to reinvigorate them, but that is a special situation.

This article is meant to get you thinking about pruning and its importance. To learn more about pruning cuts and pruning procedures, either visit https://fruit.wisc.edu/ and review the materials there or contact Scott Reuss, UW-Madison Division of Extension Horticulture Agent. Reuss can be reached via phone or email, and he can walk you through pruning processes and decision making or send you resource materials that will assist you. His contact information is sreuss@marinettecounty.com or via phone at 715-732-7510 or 715-923-0807.

Scott Reuss is the horticulture agent for Marinette and Oconto counties at the University of Wisconsin-Madison Division of Extension. Contact him at sreuss@marinettecounty.com or 715-732-7510 or 715-923-0807.