Variation in bud burst and flower opening responses of local versus non-local provenances of hawthorn (Crataegus monogyna Jacq.) in Belgium

To study the impact of provenance selection of planting stock in (re)forestation and landscape plantings, the variation in bud and flower phenology, height increment and shrub morphology was examined within and between the local and non-local provenances of Crataegus monogyna in a provenance trial. Seven Belgian provenances were included, five in Flanders and two in Wallonia, completed with three commercial provenances originating from Italy, Hungary and the United Kingdom. A completely randomized design (single tree plots) was adopted. Data were processed using mixed modelling techniques. South European provenances flushed up to 7 days earlier than the Flemish provenances, whereas the Walloon provenances flushed 4 days later. Compared to the Flemish provenances, Southern provenances and Walloon provenances flowered 4 days earlier and 2 days later respectively. Height increment and shrub morphology did not vary significantly between the Belgian and commercial provenances. Bud burst varied less than flowering among the Flemish and the Walloon provenances. This possibly indicates a higher selection pressure on bud burst than on flowering. The higher time lag between the different provenances for bud burst in comparison to flowering indicates a stronger plastic response for the latter. The results point out the importance of bud burst as an indicator of local adaptation to geo-climatologic components. Finally, it appeared that old hedges are likely to be good sources of locally adapted seed.