Herkomstenonderzoek van de Douglas in Nederland

Botany, strains and natural region (topography, geology, soil types, climate and ecology) were described for Pseudotsuga taxifolia (Poir.) Britt. in the coniferous forests of North West America. Seeds of 35 known provenances were introduced in different parts of the Netherlands between 1923 and 1930 and planted in pilot trials. Height after 10 and 15 years distinguished 4 quality classes for origin. Measurements of volume per unit area at 25 years of age did not much alter this division.
Usually firs of maritime origin, particularly from western and southern aspects, were better than those of continental origin. Different origins from a small area may give very different results, so that it is essential to look for other factors influencing tree growth, particularly inherent differences. Origins of greater height than a few hundred metres above sea level and from continental areas caused trees to grow too slowly in the Netherlands. The method of planting and the species for mixed plantations greatly influenced growth.

The more continental the climate of origin, the earlier the fir budded. The most maritime one was never injured by late spring frost. Those of continental origin suffered much from Rhabdocline pseudotsugae, while those of maritime origin were not attacked.