E.F. Gilman and J. Grabosky
Mulch and Planting Depth Affect Live Oak Establishment
Journal of Arboriculture 30: 311-317
This study was designed to evaluate the impact of several planting depths and mulch depth, particle size and placement on tree establishment. Except for one period 2 weeks after transplanting, mulch depth and mulch particle size did not affect first-year stress (stem xylem potential) or growth of 76 mm (3 in) caliper B&B transplanted live oak (Quercus virginiana Mill.). Negative effects of deep [15 mm (6 in)] mulch 2 weeks after transplanting only occurred for the mixed particle sized material. Mulch placed over the root ball intercepted water causing a drier root ball and resulting in greater tree stress and reduced survival following light applications of water then trees with no mulch over the root ball. This did not occur following heavy applications of water. Keeping the ground near trees free of vegetation chemically had the same effect on post-planting stress and growth, as did mulching. Soil over the root ball resulting from deep planting intercepted water resulting in more tree stress and greater likelihood of tree death in the first four weeks after planting. However, trees planted deeply were less stressed three months after planting. No root ball settlement occurred in the first 6 months after planting container grown trees.