Near rotation-length performance of selected hybrid larch in Central Maine, U.S.A

Twenty-two year measurements of a test of inter- and intraspecific larch hybrids among European (E), Japanese (J) and tamarack (T) parents growing in central Maine reveal significant hybrid vigor, especially among crosses involving J and E parents. The mean heights and diameters of all the interspecific crosses between J and E parents exceeded those of intraspecific crosses among either of the parents. The mean height after 22 years for all 17 JxE and ExJ crosses was 19.2 m (63 feet), which compares favorably with heights of loblolly pine plantations at age 25 growing in the southeastern USA, where site index ranged from 12.2 m to 24.4 m (40 and 80 feet respectively). In addition the mean height of these larch crosses was 30% greater than that of a control hybrid seed lot of German origin. Crosses between E and T parents also performed well, but exhibited relatively poor form, and seed set was very low. Seed set and viability for crosses between J and E were as good as intraspecific parental crosses. Therefore propagation of hybrid larch crosses via controlled pollination and rooted cuttings is feasible, and the potential benefits of larch plantations for Maine’s forest economy are briefly discussed.