An operational root wrenching trial at Humboldt Nursery

Size control of Douglas-fir seedlings to be planted on the Glide Ranger District of the Siskiyou National Forest was first tried in August of 1974. At that time, the 2-0 seedlings were 56 centimeters tall (22 inches) with a small root mass; a poorly balanced seedling. It was known that seedlings with such large tops and small roots were customarily difficult to handle during outplanting, and could not be expected to survive and grow well. Therefore, a decision was made to top prune seedlings at 30 cm. (12 inches) and undercut the roots at 20 cm. (8 inches). This treatment was found to produce well-proportioned stock with good caliper, dark green foliage, and many buds. The following year, all Glide stock was undercut in early July and wrenched in mid-August to improve balance and planting ease. One lot was wrenched at 15 cm. (6 inches), all others were wrenched at 20 cm. (8 inches). Differences could not be distinguished between seedlings from lots wrenched at different depths. Tops were not pruned. Stock was later judged to be excellent for intended planting sites. Field contract inspection records revealed near zero "J" or "L" rooting, so treatment was deemed a success from this standpoint. Survival and growth of wrench versus non-wrenched stock is being evaluated, but data is not yet available.

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Author(s): James W. Edgren, Mel Greenup, James M. Reynolds

Publication: National Nursery Proceedings - 1978

Event: Nurseryman's conference and seed processing workshop
1978 - Eureka, CA