Obtaining and Planting Your Trees - Growing Organic Orchard Fruits - page 350

When the trees are spaced more than about 12 feet apart, you can use the
tractor and reference bar method to locate the planting holes. Set the bar
length to mark one-half the desired in-row spacing, place the reference point
of the bar over a block-end reference line, and plow at right angles to the
planting rows (see figure 7.4 ➔ ). Mark every other furrow intersection point
in each row with a flag or stake. This design creates a triangular planting
that maximizes the distance between trees in adjacent rows.
FIGURE 7.3
Laying Out Planting Rows with Tractor