By Robert Crassweller
While it may be a national holiday, fruit growers should think about trying to plant their trees as early as possible. At the winter fruit schools, a number of growers were concerned about being able to plant new orchard blocks this spring. All the rain from last year has left many orchard sites converting from snow banks to mud pits.
Trees planted early have an advantage over one planted later. Root growth usually is initiated once soil temperatures reach 45°F and warmer. Last year at Rock Springs the daily average soil temperature rose above 45°F and stayed there beginning on April 22. Obviously in more southern areas of PA soil temperatures will warm up sooner. The big advantage of early planting is to promote root development before there is any shoot growth. When planted later, trees are exposed to warmer temperatures that will cause the buds to break sooner and may struggle due to the lack of regeneration of new root systems.
Some growers have thought to get around this early spring time crunch by trying to plant trees in the fall. When I worked in Georgia, this was a pretty standard practice especially for peaches, for two reasons. First, many nurseries were able to produce ‘June-budded’ trees that could be dug in the late fall. These trees, although smaller in diameter, established quicker. Unfortunately, many northern nurseries do not have the capability, workforce, or time to be able to dig and ship trees at that time of the year.
The other advantage that southern orchards have is that they usually do not experience any of the severe cold temperatures that we can in the Mid-Atlantic region. At Rock Springs we had several below 0°F days the last few days January and first few of February. I have planted trees at Rock Springs in November, as part of a class exercise. However, one year I did lose some to cold damage. With the new cultivars we are planting and the associated royalties it is not worth the risk of planting in the fall.
Storing the trees
When a nursery ships trees to you it is important that you handle them properly. First, inspect them when they arrive. Make sure they have not dried out or that there are any signs of root damage or emerged shoots. Unpack the trees from their containers and add moisture, moist shavings, or shredded paper to prevent the roots from drying out. Trees should be stored in well-ventilated cold storage above 32°F until you are ready to plant. Do not store trees in coolers that have held apples or other climacteric fruit unless the room has been well aerated to remove any residual ethylene. If trees are to be held for more than a few days, they should be “healed-in” with sand or sawdust, and the medium should be kept moist.
The day before planting, if possible, hydrate the roots by placing them into a stream of flowing water for 4 to 18 hours. We had a small flowing stream coming down from the mountain ridge above Rock Springs that we often used. Alternatively, we used large trashcans filled with water and then transported them to the field in the trash cans.
Preparing the field
Make sure the soil that you will be planting in is workable, and it should be dry enough to crumble in your hand. Most commercial growers utilize a tree transplanter. If doing so, be sure the row ends are marked off. Only place enough trees in the planter trays that can be planted before the roots begin to dry out. It helps to have a “nurse truck” to bring a new supply of trees from the holding area.
Using a tree planter.
One person should follow the transplanter to adjust the graft union up or down to prevent scion rooting (too deep) or tree leaning (too shallow) after the tree is set. In recent years and with some training systems the bud union may be kept out as much as 6 inches above the final soil line. The purpose of the “high planting” was to induce greater root shank exposure and cause greater dwarfing. I still subscribe to the “3 to 4-finger depth rule”. That rule is to set the bottom of the bud union at the height of the width of an adult’s three to four finger width (approximately 2.5 to 3.0 inches). I believe we have enough different rootstocks that proper rootstock selection will be a better method of achieving the tree size control. Excessive exposure of the rootstock shank only encourages the development of burr knots that may girdle the tree and serve as entry points for boring insects.
The result of planting union too high.
If planting is done using an auger, holes can be dug the previous day. If the soil is too wet when the holes are augered be sure to scrape the side of the hole to break up “glazed” hole sides.
Augering holes for planting.
Regardless of the method used to plant the trees, the person following the planting process should immediately check the graft union height. I have found it is easier to pull a tree up right away if it is planted too deep than it is to replant a tree that is initially set too deep.
Bud union height of 3-4 fingers.
The sooner newly planted trees are watered, the better the soil contact with the roots will be, and better growth will begin. If the irrigation system is not set within a matter of days, follow with a watering tank to add water around the base of the tree to bring roots and soil in close contact with each other. Too often, newly planted trees do not get off to a good start because the rainfall the local weather reporter predicted does not materialize. We should take a tip from our vegetable grower friends; they would never transplant vegetables without having the capability to irrigate immediately after planting.
Watering trees from a water wagon after planting.
Finally, we like to return the next day and apply a 5000 ppm solution of 6-benzyladenine mixed in white latex paint to buds to induce their growth. Returning the next day also allows a second inspection of the bud union depth to insure proper placement. Trees are also still dormant at this point.
Tree treated with 5000 ppm 6-BA mixed with white latex paint the day after planting with growth the following year.