Desmond R. Layne
With the launch of our “Everything About Peaches” website in July 2010 (www.clemson.edu/peach), one continuously growing component of the site is the FAQ (Frequently Asked Questions—and answers!) section. Currently, we have a total of 32 FAQs on the site. These are arranged in five different categories including historical interest, general interest, peaches in China, scientific findings, and commercial production. In as many cases as possible, I have sought to utilize high-quality photos and captions to illustrate the topic.
When you read a particular FAQ on the site and you get to the bottom, you should see “Learn more: read column, watch video, etc.” with a link to additional complementary information that is available on the site. Three of the most recently added FAQs are noted below. Please visit the FAQ site to see the photos and captions at: www.clemson.edu/extension/peach/faq/.
Q. What problems can result if a peach tree is planted too deep?
A. Most fruit trees are grafted in the nursery about 2 to 4 inches above the soil line. Bareroot grafted trees that you purchase from the nursery should have a visible “soil line”—that line on the trunk where the soil came up to at the time the tree was dug prior to shipping. Ideally, when this bareroot tree is planted in your orchard, you should ensure that the same soil line on the bark is at the actual level of the settled soil after planting. A good rule of thumb, therefore, is to ensure that the graft union is 2 to 4 inches above the soil once planted.
Because of the convenience of using tractor-mounted tree planters to plant thousands of trees per day, if the resulting furrow is too deep, many trees can be planted incorrectly in a short period of time. In some cases in commercial orchards, I have observed trees planted eight or more inches too deep. This is particularly a problem on heavier soils. Planting too deep can stunt tree growth, lead to soil compaction and a lack of oxygen for feeder roots, and even adversely impact tree stability. Under conditions such as these, if soils become saturated because of excess rain, trees may die from water logging or may be predisposed to infection by phytophthora root rot.
Q. What can happen if peach trees get flooded or if the soil they are planted in remains saturated for more than 48 hours?
A. Peach trees definitely do not like wet feet. Soil saturated conditions for 48 hours or longer is enough to kill a peach tree. Ideally, trees should be planted on sites where there is good surface drainage during periods of torrential rains and also good internal drainage. Trees should not be planted in low spots—for one, water can stand there; for two, cold air can settle there and cause spring frost damage. Heavy clay soils or sites with a hard pan near the surface of the ground impede water drainage and can result in soil-saturated conditions following rainfall. In some cases, use of raised beds can help if the site is otherwise suitable.
Under non-saturated conditions, oxygen in the soil air spaces is available to support root respiration and good root health. However, when the soil becomes saturated with water, aerial oxygen is displaced from the soil air spaces. Under these conditions, root respiration is impaired, free nitrates are lost, and the toxic end-products of bacterial respiration can build up. Further, trees may be predisposed to infection by phytophthora root and crown rot since this fungus can spread by motile (they can swim) zoospores.
Q. How does hail adversely impact peach trees?
A. Peach trees and hailstorms do not go well together. Hailstorms can vary in intensity, duration, and when they occur during the growing season. Hailstones can vary in size and structure. Some commercial growers have hail cannons in their orchard for use when a hailstorm is approaching. Scientific and anecdotal evidence presents differing viewpoints on whether the use of hail cannons provides economic benefit.
In general, when hailstones fall on an orchard, considerable damage usually results. This damage can include all of the following: tattered leaves, broken or damaged shoots, wounds on scaffold branches, fruit damage, and even fruit being knocked to the ground. Depending on the extent of damage, a grower may decide to thin off damaged fruit and manage the rest or he may decide to simply abandon the block altogether and hope for better luck next year.
Generally speaking, the latter would be a poor management decision. Open wounds on the growing shoots, branches, and scaffolds present entry points for bacterial and fungal pathogens and also insects (i.e., lesser peach tree borer). The grower should maintain a minimal pest management program that will protect trees during the wound healing process and not predispose trees to further damage. Otherwise long-term health, productivity, and longevity of the orchard may be severely compromised.
Finally, do you have any questions of your own that I should add to the website for the benefit of all growers nationwide? If you do, please contact me directly—I will keep your suggestion confidential and anonymous. No question is a “dumb” question. When I visit a farm where hundreds of trees are dying because they were planted too deep on heavy soils, or they were flooded in a low spot after torrential spring rains, or they were abandoned after a hail storm (as above), it may be impossible to bring such trees back to viable productivity.
In the two former situations, proper planting depth and site selection could have avoided the problems altogether. In the latter (hail), this may not have been preventable, but aftercare might limit long-term damage and promote healing such that the orchard could be productive next year. Proper planning and informed decision-making can help ensure future success. As Ben Franklin was quoted saying, “An ounce of prevention is worth a pound of cure!”
This column by Dr. Desmond R. Layne, “Frequently Asked Questions” appeared in the May 2011 issue of The American Fruit Grower magazine on page 48.
Desmond R. Layne, Ph.D., is an associate professor of pomology, tree fruit specialist, and state program team leader for horticulture at Clemson University. He is also president of the American Pomological Society.
For more information, go to www.clemson.edu/peach.