Effect of planting depth on growth of open-rooted Pinus elliottii and Pinus taeda seedlings in the United States

Three studies in the Coastal Plain of Georgia were remeasured 7 or 8 years after planting to determine the effects of planting depth on field performance of open-rooted seedlings [root-collar diameter (RCD) ≥ 5 mm]. Average planting depth (i.e. shoot height before planting minus shoot height above ground after planting) for machine planted P. elliottii was 14 cm while hand-planted P. taeda seedlings averaged 9-11 cm deep. P. taeda showed no adverse effects on growth when planting seedlings up to 15 cm deep. Data for machine planted P. elliottii indicated that seedlings were planted 9 mm deeper on double-beds than on single-beds. Small-diameter pine seedlings (< 5 mm RCD) were not planted as deeply as seedlings with large diameters (RCD > 5 mm). For P. elliottii planted on double-beds, seedlings planted more than 15 cm deep had slightly smaller diameters at breast height than seedlings planted 10 cm deep. Although most tree planting guides recommend planting seedlings 7,5 cm deep or less, many company plantations have been established by planting at greater depths.