Its All About Light

Gordon Johnson, Extension Fruit & Vegetable Specialist;

Production of high yields of quality fruit requires adapted varieties, close attention to disease and insect management, balanced plant nutrients, and good weather conditions. One of the other key areas that growers need to consider is light. Leaves require adequate light levels to produce sugars by photosynthesis. These sugars are then translocated into developing fruit. Sugars also provide the building blocks of other flavor components. With this in mind, a very important aspect of fruit management is to insure even light distribution throughout the plant canopy. This applies equally to small fruits and tree fruits.

The following are some considerations to achieve this even light distribution and to manage for the best combination of yield and fruit quality.

1) Play close attention to plant densities and do not overcrowd plants. While more plants often means higher yields, excess shading at high populations can lead to reduced quality. Crops like matted row strawberries bear the most fruit and best quality fruit on the edges of the row. In most fruit crops, fruits on the interior of dense canopies often have poorer color, reduced sugars, and poorer flavor.

2) Choose pruning and training systems that allow for even light distribution. In fruits such as peaches, this is achieved by pruning so that scaffold branches are arranged in a open form V or vase shaped form. In crops that use a central leader system such as apples, it means pruning to appropriate spacings and orientations between scaffolds to allow for good light penetration. In summer bearing brambles, this means having trellis wires arranged so that fruiting canes are to the outside where they can receive the most light and training new canes to the in the middle. Pruning canes higher will also allow for more light along the length of the cane, however, they should not be so tall that they shade neighboring rows.

3) Thinning fruiting material and thinning foliage is often necessary for good fruit quality, color development, and uniform ripening. Leaf thinning is practiced in grapes for this reason. Thinning of blueberry canes to remove old and weak material is another example as is detail pruning of many tree fruits to remove excess fruiting wood and allow in more light.

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