Apple Scion/Rootstock Selection and Planning for Michigan
Updated January 2008
The training system that an apple (Malus x domestica) grower selects must be one which best maximizes all the resources in making the enterprise a profitable venture. There are many parts to the orchard system decision "puzzle" which must fit together in a complementary arrangement to gain maximum precision and profitability. The most immediate question that must be answered regarding the establishment of a new orchard is spacing. Extension agents and growers often need assistance in determining optimum tree density for sites. Trees planted too close, cause excessive shading and competition for resources results in inadequate light penetration, poor quality fruit, low cropping, excessive labor in pruning to reduce shading impact, etc. Excessive distance results in inefficient planting designs where the land surface is under utilized. In 1989, we made an initial attempt at trying to simplify the decision making process by considering the most important variables and assigning them values (number codes in parentheses) in a formula. Assessments on vigor are derived from rootstock and cultivar trials and field observations. Our experience gained from working with the high density orchards and with new cultivars and rootstocks has encouraged us to frequently update the model. The formula is available on the Michigan State University Department of Horticulture web site for general use by the public, students and extension field agents in an interactive mode (spacing calculator) and below. Still more revision in the future will be necessary as we learn more of the technical intricacies of new rootstocks, cultivars, marketing demands and management constraints.
The primary factors affecting spacing include; scion vigor, rootstock vigor, soil type, irrigation, management system and the interactions that take place between them. This spacing recommendation is only relevant to Michigan sites and for single row arrangement of trees -- use good judjment when applying to other situations. Use the on-line form below (enter values) to calculate in-row tree spacing based on your input:
For the iPhone/Safari Mobile (or simplified version) of this calculator, click here.
The formula and calculation:
In-row tree spacing.
Scion (C) + Rootstock (R) + Soil (S) + Irrigation (I) + Management System (M)
(where high density systems are applied, multiply sum by factors noted in Management category)
Row spacing width.
North/south direction; 1.3 times expected or projected tree height. (For East/West row direction, use 1.5.) Tall Spindle limited to 10 ft. height.
Example 1: Idared / M.26, sandy (droughty) soil, drip irrigated, on stakes, expect 12 ft. high tree:
In-row tree spacing = (2 + 2.5 + 1 + 2 + 0) = 7.5 feet
Row spacing = 1.3 x 12 = 15.6 feet
Recommended tree spacing = 7.5 x15.6 ft
Trees per acre = 372
Example 2: McIntosh / MM.106, sandy soil, no irrigation, low intensity, expect 14 ft. high tree:
In-row tree spacing = (4 + 7 + 0 + 0 + 3) = 14 feet
Row spacing = 1.3 x 14 = 18.2 feet
Recommended tree spacing = 14 x18.2 ft
Trees per acre = 171
Ex. 3: Jonagold / M.9 EMLA, fair vigor soil, drip irrigated, Vertical Axis, expect 10 ft. high tree:
In-row tree spacing = (3 + 1 + 2 + 2 + 0) * 0.7 = 5.6 feet
Row spacing = 1.3 x 10 = 13 feet
Recommended tree spacing = 5.6 x13 ft
Trees per acre = 598
Ex. 4: Empire / Mark, vigorous clay loam soil, drip irrig., slender spindle, expect 8 ft. high tree:
In-row tree spacing = (2 + 0.5 + 3 + 2 + 0 ) * 0.6 = 4.5 feet
Row spacing = 1.3 x 8 = 10.4 feet
Recommended tree spacing = 4.5 x 10.4 ft
Trees per acre = 931
For a complete list of references, see the complete publication Apple Scion and Rootstock Selection and Planning for Michigan.
Copyright©2008 Jon Clements and Ron Perry