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

Abstract

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.
Key words: Pinus elliottii, Pinus taeda, Survival, Seedling quality, Planting quality, Reforestation