Growing Large Fruit on Trees a Challenge (growlrgfruit)

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Growing Large Fruit is a Challenge

by Don Janssen, UNL Extension Educator

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A common question from individuals who are growing fruit trees in the home landscape is "Why are my apples so small?" Growing large fruit can be a challenge for fruit growers.

During the first several weeks after bloom, fruit tissues grow by cell division. This is referred to as the exponential phase of growth, with many cells dividing simultaneously. As the number of cells increase, fruit growth occurs at increasingly faster rates. Near the completion of cell division, cells that are no longer dividing begin to expand. Cell expansion continues for the remainder of the season and accounts for the majority of fruit growth.

Several factors can limit fruit growth. Unless freezing spring temperatures reduce the number of viable fruit blossoms, fruit trees tend to set many more fruit than they can grow to optimum size. The large number of fruit compete for limited plant resources–most likely carbohydrates or nitrogen. This competition inhibits fruit growth, especially during cell division. For this reason, it is best to reduce fruit numbers early in the season through a process known as fruit thinning. Fruit size improves following hand removal of excess fruit early in the growing season.

A "rule of thumb" is to space apples six to eight inches apart, leaving only one apple per spur. Since an apple tree can develop an alternate bearing habit (a heavy crop of small fruit one year followed by no or few fruit the next), it is important to thin within a month after bloom. With experience, you will learn to balance crop load to tree growth.

To complicate things even more many environmental factors similarly influence fruit growth. Cool temperatures during cell division result in reduced growth rates. Additionally, periods of cloudy weather early in the season limit the availability of carbohydrates, which restricts fruit growth. In cases where the growth rate of some fruit is severely limited, they will drop prematurely. Drought stress, nutrient deficiencies and heavy insect or disease damage can likewise reduce fruit growth.

This resource was added April 2008 and appeared in the Lincoln Journal Star Newspaper Sunday edition. For information on reproducing this article or using any photographs or graphics, read the Terms of Use statement

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University of Nebraska-Lincoln Extension in Lancaster County is your on-line yard and garden educational resource. The information on this Web site is valid for residents of southeastern Nebraska. It may or may not apply in your area. If you live outside southeastern Nebraska, visit your local Extension office

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