Pruning Acer rubrum at Planting Impacts Structure and Growth After Three Growing Seasons

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Figure 1.
Pruning on primary branches >0.5 aspect ratio was accomplished in one of three ways: 1, 2, or 3. Sections A, B, and C were measured for each of the five primary branches with the largest diameter.

Table 1.

Response of Acer rubrum L. ‘Florida Flame’ three growing seasons after structural pruning at planting.

Measured tree attribute	Pruned at planting	Not pruned at planting	% reduction from pruning^{^z}
Trunk diameter increase (cm)	5.6 b^{^y}	6.1 a	8
Tree height increase (m)	2.5	2.7	ns^{^x}
CSA^{^w} of five largest-diameter branches (cm²)	41.3 b	55.5 a	26
CSA of largest-diameter branch (cm²)	14.2 b	20.6 a	31
Distance from top of tree at planting to the union of the highest branch that is among the five largest (m)	0.7 b	0.9 a	22
Aspect ratio^{^v} of the five largest-diameter branches	0.55	0.59	ns
Aspect ratio of the three largest-diameter branches	0.60 b	0.67 a	10
Aspect ratio of largest-diameter branch	0.68 b	0.76 a	11
CSA of largest-diameter branch with bark inclusion (cm²)	11.0 b	16.1 a	32
Size-ratio^{^u} (cm²)	4.5 b	6.5 a	31
Size-ratio on branch with largest CSA (cm²)	9.7 b	15.5 a	37
Number of five largest-diameter branches with an inclusion in the union	3.1	3.3	ns
Percent total CSA with inclusions in union	40.7 a	52.6 b	23
Bending stress to pull trunks to five degrees (MN/m²)	22.2	21.7	ns

↵^z Percent reduction = (not-pruned − pruned)/not-pruned × 100.
↵^y Means within rows followed by the same letter are not statistically different (t-test) at P < 0.05.
↵^x ns = P > 0.05.
↵^w CSA = cross-sectional area.
↵^v Aspect ratio = branch diameter ÷ trunk diameter just beyond union.
↵^u Size-ratio = branch CSA × aspect ratio.