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Thread: Peach trees frost survival
07-25-2009, 01:45 AM #1
- Join Date
- Jul 2009
Peach trees frost survival
I farm peaches in the mid-section of South Carolina. Typically my trees begin to bloom around March. Unfortunately, because of the weather here in S.C. we often get cold temperatures into mid to late April. This obviously results in the killing of my peaches.
Over the years I have gone to great lengths to save my peaches by placing large plastic sheets over the trees on nights were temperatures are expected to drop. Unfortunately this can be quite costly b/c the trees tear through the plastic so I have to purchase new material every year.
Does anyone know of an affordable solution that may help me here? I have thought of a light nylon material (maybe like parachute material) to throw over the tree. I'm hopeful that this will be sturdy enough not to tear but light enough not to break my branches.
I have around 250 trees and would like to spend less than $20 per tree. I would appreciate any help provided.
07-27-2009, 09:27 PM #2
- Join Date
- Jan 2007
I found quite a bit of info on this situation. It looks like you are already headed in the right direction. I found 2 really good sites with info on what you are doing currently with the plastic blankets & also a few other options you may consider depending on your location & situation. Also, if you do a search on google for a "frost blanket" you will find info on this type of product. While I do not have any experience with them, there were also several sites that did. Please see below & I hope this helps!
How to Protect Fruit Trees From Late Spring Frosts
By Janet Harriett
eHow Community Member
When the fruit trees think it is spring and Jack Frost has other ideas, a late spring frost can doom an entire year’s crop in a home orchard and commercial orchard alike. The measures that commercial orchards take are not feasible for the backyard orchard with just a few trees. Here is a quick and inexpensive [COLOR=darkgreen ! important][/color]way to protect a small-scale fruit planting from freezes that come after the trees break dormancy.
Difficulty: Moderately Easy
Things You'll Need:
- 30 gallon plastic trash bags
- Duct Tape
- Gallon jugs (at least 1-2 per tree)
- Rocks, bricks, logs, or other heavy items
First and foremost, you want to keep as much heat as possible near the tree by tenting over the tree with plastic. To construct protective tents, start by laying out plastic trash bags flat on the floor and sealing the open ends with a strip of duct tape along the length of the open end of the bag. Overlap the edges slightly and tape enough bags together to make a large sheet at least as tall as the tree and as wide as half the circumference of the canopy at its fullest point.
Make a second sheet, the same size and lay the two sheets on top of one another, lining up the edges.
Tape the top and sides of the two sheets together by folding a strip of duct tape from the front to the back. Be sure to leave the bottom open. This should leave you with something that looks like a much larger plastic trash bag.
Fill gallon jugs with warm water and place several at the base of the tree. Be sure to leave at least an inch of headspace at the top of the jug and keep the lid loose, just in case the water freezes. The water jugs act as a heat reservoir, releasing heat gradually over the night to keep the temperature around the tree warmer.
Cover the trees by sliding the open end of one of the plastic covers over each tree and carefully pulling the plastic down around the canopy. This can be tricky in a breeze. The plastic should reach all the way to the ground and the water jugs should be inside the plastic.
Weigh the bottom of the plastic down with stones, small logs, or whatever is handy. Try to make sure there are no gaps around the bottom of the plastic. The goal is to make sure that any heat that radiates from the ground or the water jugs gets trapped inside the plastic tent.
If daytime temperatures heat up above freezing, remove the plastic during the day so the tree does not bake. Replace whenever the temperatures threaten to go below freezing.
Tips & Warnings
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- The same method can be used for early blooming ornamental plants like forsythia.
- This method works best with smaller trees, either dwarf trees or standard trees that are less than 4 or 5 years old. For larger trees, complete tenting might not be feasible, but you can still get some measure of frost protection by covering the top of the canopy with row cover material, old curtains or bedsheets, or by stringing outdoor holiday lights through the tree and keeping them on while the temperature is low.
- The plastic tent will also keep pollinating insects away from the tree, so make sure to remove the tent as soon as safe if the tree is in full bloom. The pollinating insects might not be out during a cold snap, but if they are, it is important that they have access to the blooms if they are out.
- A covered tree is more susceptible to winds. Use extreme caution tenting a tree if the cold temperatures are accompanied by windy conditions.
07-27-2009, 09:40 PM #3
- Join Date
- Jan 2007
This information I found from Penn State University. http://resources.cas.psu.edu/TFPG/AGRS45part01-10.pdf
Frost Protection for Tree Fruit
Frost causes the loss of a certain percentage of tree fruit crops almost every year. Susceptibility to frost damage depends on a tree’s stage of development, variety, and location, but certain preventative measures can be taken. The goal of all frost protection methods is to maintain the blossom temperature above the critical temperature.
Only a few frost protection methods have been consistently effective over the years. These vary considerably in cost, management time, and effectiveness. It is very important to get a good estimate of actual economic losses caused by frost before deciding whether to implement a frost protection system. A small average annual loss of crop to frost may not be worth the time and money invested in a protection system.
Selecting the Right Site
When air near the ground cools, it becomes denser. If the ground is sloped, the colder air will flow downhill into a pocket or onto level ground. Therefore, planting the orchard on a hill is the first step in frost protection, because there is nothing to trap the cold air as it drains. In some cases, cold air drainage may protect the crop from frost enough that no other method is necessary. However, if a good sloped site is not available or a site already established is experiencing frost damage, other protection measures may be required.
Burning combustible materials to protect crops from frost originated thousands of years ago. This is the most effective way to maintain the temperature above the critical level, but it is also the most expensive and environmentally damaging. Stack heaters, still available from selected distributors, burn fuel oil stored in the heater’s base or injected through nozzles from a fuel line. The heaters often have a diffuser on the top to spread out the flume. Trees are heated through radiative transfer directly from the heaters or from air warmed by them.
Using water to protect blossoms from cold has gained popularity over the last couple decades. Compared to heating, irrigation for frost protection lowers expenses and reduces environmental damage. Irrigation lines can also be used for soil moisture maintenance, chemical injection, and heat suppression. Although water use can protect against frost, it involves greater risks than heating. Overuse of water can saturate soils, increasing the likelihood of diseases, and build up ice, which may damage trees. Water application rates depend on the desired bud temperature (buds in earlier stages of development are hardier and therefore have lower critical temperatures), air temperature, humidity, and wind speed.
Applying water directly to flower buds allows the heat released from freezing water to maintain a bud temperature near freezing, which is a few degrees above the critical damaging level. As long as the rate of water being applied and the rate of freezing are balanced, bud temperature will remain close to the freezing mark. Insufficient application can do more damage than no protection at all, because evaporation may cause flower bud temperature to drop below air temperature.
One problem with overtree sprinkling is not knowing how much water to apply. Application rate models have been developed by modeling the energy balance between heat lost from the buds as a result of environmental conditions, and heat gained from freezing of the water. Rates for different conditions have been determined using the sprinkler application rate model FROSTPRO (Perry, 1986) and are shown in the table below. Note that lower humidities will increase the application rate.
(see attached chart)
The principle behind pulsing (or cycling) of the irrigation system is that the rate by which water is delivered to the orchard can be varied by turning the water on and off in short cycles, e.g., 2 minutes on and 2 minutes off. First, determine the fixed rate of the sprinklers. If it is not known, you can determine the application rate by placing buckets in a grid pattern in the orchard and sprinkling for one hour. Measure the depth of water in the buckets, and use the average application rate in inches per hour. For example, if the fixed rate is 0.20 inch per hour, and the recommended rate is 0.10 inch per hour, the cycle would be something like 2 minutes on and 2 minutes off. The on time should not be less than the time for a sprinkler head to make a complete rotation, and it is not recommended that the off time exceed 3 minutes.
A sprinkling technique that is gaining acceptance is the use of undertree sprinklers to protect trees from frost. How this method works is not completely understood, but it is believed that the heat released as water vapor condenses on leaves and blossoms keeps buds above the critical temperature. This approach uses less water, and there is little or no damage to the tree as a result of ice buildup; but certain blossoms, especially those at the top and exposed to the sky, may receive inadequate protection.
The lowest several hundred feet of the atmosphere become stratified under calm, clear, frost conditions. An inversion condition thus exists, meaning that temperature increases as it rises to the top of the inversion layer. A wind machine mixes the warmer air from the upper portions of the inversion layer with the colder air near the ground, raising air temperatures around the trees by a few degrees.
Wind machines are motor driven and therefore consume fuel, although not nearly as much as stack heaters. They work under calm, clear conditions as long as the frost is not too “deep”; that is, temperatures are not more than three or four degrees below the critical temperature. Wind machines do not work under cold, windy conditions, because the wind usually mixes the atmosphere enough to prevent an inversion layer from developing.
When using wind machines, it is important that the machines are turned on when the air temperature in the orchard is still above critical temperatures. If air temperature is being monitored in a protected shelter within or outside of the orchard, the machines should be initiated when the air temperature is still above 32oF. It is very possible that bud temperatures may be several degrees below the air temperature due to radiative cooling, and they can experience damage even if the air is still above freezing.
More information about choosing and implementing frost protection systems can be obtained from your county extension specialist or from commercial dealers that offer frost protection systems and components.
Critical Temperatures for Various Fruits
The temperature at which fruit buds are injured depends primarily on their stage of development. As flowers begin to swell and expand into blossoms, they become less resistant to freeze injury.
Not all blossoms on a tree are equally tender. Resistance to freeze injury varies within trees as it does between orchards, cultivars, and crops. Buds that develop slowly tend to be more resistant. As a result, some buds are usually killed at higher temperatures, while others are resistant at much lower temperatures. Table 1-25 shows the average temperatures required to kill 10 percent and 90 percent of buds. Consideration should also be given to weather conditions preceding cold nights. Prolonged cool weather tends to increase bud hardiness during the early stages of bud development.
Table 1-25. Critical temperatures for various fruits
Table 1-26. Management practices for apples and stone fruits
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