Grow just one variety. Growing one variety will limit your marketing season and the number of times consumers can come back to buy more peaches.
On the other hand, growers who want to sell lots of peaches will select multiple varieties that will ripen over a six- to eight-week period so that the harvest season can be extended and repeat business is possible. For roadside retail sales, it is essential to have enough acreage of varieties with overlapping maturity dates to ensure a continual supply of fruit. A gap of even a week or two takes you off the market and might make it difficult to lure customers back.
Put away your pruning shears. If you don’t take the time and effort to prune trees properly in the winter, you could end up with reduced yields, tree damage and poorer-sized fruit that doesn’t satisfy customers. Dormant pruning to limit the number of fruiting shoots is actually a great “thinning” technique to reduce future crop load. Removal of weak, shaded-out wood, diseased or dead wood, water sprouts, and root suckers is vital.
Tree height can be controlled by cutting back the top portion of the tree to less vigorous, outward growing branches or to a side branch. Maintain a consistent tree height or much of the crop may be too far above ground for convenient picking and pest control.
If fruit quality and yield diminish in older trees, heavy, careful pruning may be necessary to restore tree shape and allow more sunlight to penetrate the tree’s interior.
Ideally, summer pruning should be done about three to four weeks before harvest and limited to removing strongly vigorous, upright, nonfruiting current season shoots in the interior of the tree that cause shading and are strongly competitive for water and nutrients.
Summer pruning helps to ensure that adequate sunlight is available for proper coloring of the current season’s crop and also production of flower buds for next years crop. Because it helps to reduce the dense leaf area and high humidity within the canopy, it can facilitate more rapid leaf and fruit drying, better pesticide penetration and deposition, and reduce disease pressure.
Keep every piece of fruit on the tree. Without adequately thinning the crop, you risk producing fruit that are smaller than customers prefer and having inconsistent production from year to year. Because peaches have a tendency to overbear, if the crop load is too heavy, limbs will break when the fruit enter their final swell phase of fruit growth.
This can cause permanent structural damage to the tree and provide entry sites for wood boring insects. Trees should not be allowed to bear fruit for the first two years after planting so that all of the energy can be used to “grow the tree” and facilitate strong scaffold branch development that will support future crops. Once the trees begin to bear, careful fruit thinning is necessary for producing high-quality, marketable peaches. There are no shortcuts.
Thinning is a labor-intensive process that is expensive for the grower. Generally, early maturing varieties should be thinned first, before mid- or late-season varieties.
Timing is critical for thinning to be beneficial. Thinning during the cell division phase of fruit growth (prior to pit hardening) will have the greatest positive impact on fruit size. Depending on variety, this may be within the first 40 days after bloom. Thinning early varieties after the pit hardening does not increase fruit size substantially. With mid- and late-season varieties, thinning can be delayed until after the first drop through June drop (the second period of fruit drop) but no later than pit hardening. Earlier is better.
The amount to thin from a tree depends on the tree’s size and bearing capacity. Obviously, trees in poor vigor should not be allowed to bear as much fruit as healthy, vigorous trees. If a tree has set a uniform crop of fruit, a general rule of thumb is to thin fruit six to eight inches apart on the shoot or to a particular number of fruit per tree. After a spring freeze, however, the crop is sometimes borne on the basal portion of the shoots. In this case, only light thinning is recommended. Clusters of fruit should be broken up so that orchard sprays can cover the surface of each fruit thoroughly.
Thinning relies heavily on hand labor. Breaking up fruit clusters with a pole with rubber hose on the end (Kentucky bumper) or using aplastic baseball bat to knock the fruit off is a popular thinning method. High-pressure water sprays, tree shakers, and rope drags have been relatively unsuccessful and are not recommended.
Ongoing research has been conducted for blossom thinning with a mechanical string thinner (i.e., Darwin) with promising results but proper, uniform tree architecture is necessary for this tool to work properly and efficiently. Chemical thinning is an ongoing area of research with mixed results from year to year.
Let pests take care of themselves. Insects and diseases are very happy to make a meal out of your peaches before you or your customers get a chance to. They will also be very happy to munch on your trees.
Numerous pests directly damage the fruit and indirectly damage the leaves, branches, trunk and even roots of peach trees. In the southeastern United States, brown rot has become more difficult to manage because of resistance to key fungicides. Scientists at Clemson University have developed a tool to rapidly determine location-specific fungicide resistance profiles in brown rot.
The in-field test kit can be used in specific orchards to find out how sensitive the brown rot there is to the most commonly used classes of fungicides. The most effective spray program can then be identified for that location. The general recommendation is to rotate fungicide classes for each subsequent spray. For more information check the Web site http:peachdoc.com and look for the “Profile” link under the “Brown Rot” tab.
Don’t disturb your picking crew. An untrained crew is likely to pick peaches of variable maturity. Green fruit will never soften properly and be edible, while overmature fruit that is soft will be difficult to deliver in good condition. Repeat sales can occur only if the consumer is pleased with your product.
Unlike cherries, peaches must be picked several times over the course of 10 to 14 days to ensure that the fruit is harvested at the proper stage of maturity, with the crew going through the block every two to three days.
The most common problem is picking too soon. Some modern cultivars develop an almost solid red color or blush long before they are edible, which makes it difficult to assess maturity because a yellow background color is not visible.
An in-field pressure test using a penetrometer is a better indicator than color. Most commercial fruit is picked at between 8 and 12 pounds pressure. Fruit with a pressure of less than four pounds will bruise easily.
The level of maturity is a matter of personal preference if sales are limited to the roadside market. The farm manager should be going out and sampling individual blocks as harvest approaches. The manager needs to train the crew which fruit to pick and the fruit should be checked as it goes into the basket or bin.
Fruit picked at the wrong size, wrong color, or wrong maturity that has to be graded out or downgraded in the packing house is a financial loss to the grower, whereas the same fruit left on the tree for another couple of days could bring a profit.
Consumers prefer tree-ripened fruit, but fruit at this stage has an extremely short shelf life at room temperature. As a compromise, it might be better to pick the fruit two to four days before it is fully ripe. The fruit will continue to ripen normally, and the taste will be unaffected.
Cold storage (32°F) for a maximum of two weeks can help to extend shelf life. However, storage of fruit between 38 and 50°F can predispose the fruit of some cultivars to chilling injury and internal breakdown making them mealy and inedible. Generally, peaches should be handled very carefully. They are called “soft fruit” for a reason. •
Dr. Desmond R. Layne is Professor of Pomology Endowed Chair and Tree Fruit Extension Program Leader for Washington State University in Wenatchee, Washington. Contact him at: firstname.lastname@example.org.