© 1985 by Institute of Chartered Foresters
Performance and Frost Hardiness of Picea sitchensis x Picea glauca Hybrids in Scotland
Institute of Terrestrial Ecology Bush Estate, Penicuik, Midlothian
The growth of seven Picea sitchensis x Picea glauca hybrids was compared with the growth of two P. sitchensis provenances and Picea glauca var.albertiana at two sites in northern Scotland. The sites were at Aultmore (an exposed, dry site with a mineral soil) and Shin (a frosty, wet site with deep peat). They were of the type considered more suited to Pinus contorta than P. sitchensis.
At age 10, in 1984, most of the hybrids, at both sites, were about 10 and 20 per cent taller than P. sitchensis of Masset (Q.C.I.) and Ketchikan (Alaska) provenance, respectively. P. glauca var. albertiana grew very poorly, especially at Aultmore.
At Aultmore, the frost hardiness of three of the tallest hybrids, the two P. sitchensis provenances, and P. glauca var.albertiana, was tested at about 3-weekly intervals throughout 1982 and 1983. Detached shoots were subjected to artificial frosts in a programmable chamber. P. glauca var. albertiana was frost susceptible at budburst, but at all other times it was relatively very frost hardy (eg. to–10°C in mid-August). Also, the hybrids were consistently more hardy than P. sitchensis of even Ketchikan (Alaska) provenance from July onwards. However, the hybrids were less frost hardy than P. sitchensis of Masset (Q.C.I.) provenance in early spring (they dehardened a week earlier in March-April) and their buds were equally as frost susceptible at the time of budburst. In 1983, trees of P. glauca var. albertiana burst their buds about a week sooner than P. sitchensis.
It was concluded that P. sitchensis x P. glauca hybrids can perform better than P. sitchensis at sites considered ‘marginal’ for P. sitchensis, and that their good performance may be partly attributed to, or associated with, their greater summer and autumn frost hardiness. A programme of inter-specific hybridization is being pursued.