Browsing by Subject "talvenkestävyys"

Domestic supply of cranberries in Finland does not meet demand, so the food industry buys cultivated cranberries from abroad. American cranberry (Vaccinium macrocarpon Ait.) is grown in North America in areas where generally 1800 to 2500 (base 5 °C) growing degree days (GDD) accumulate during the growing season. Cranberry cultivation has been tried in Finland for a few occasions. From the experiments it has been concluded that in Finland winter is too cold and the growing season is too short for the commercial cultivation of American cranberries. However, growing season can be extended, and the conditions of cultivation can be influenced using protective covers. For example, in high tunnels, more GDDs accumulate than under field conditions. The objective of this study was to evaluate the effect of high tunnel on the growth, development and overwintering of seven V. macrocarpon cultivars in potted cultivation in Viikki (60 °N, 25 °E). More above-ground biomass was accumulated in high tunnel than under field conditions. In general, the runners (stolons) grew faster in the tunnel than in the field. Faster growth was explained mainly by the excess of 200 GDDs accumulated in the tunnel. However, not all cultivars responded similarly to high tunnel conditions. For example, 'Ben Lear' may have suffered from stress caused by the more fluctuating air temperature and consequent difficulties with the automated irrigation settings. Irrigation was adjusted by the needs of more high-growth ‘Howes’ and ‘Prolific’ cultivars. Interestingly, the root growth response to high tunnel treatment was highly different from the above-ground shoot growth. Except for ‘Prolific’, root growth was more extensive under field conditions. All plants overwintered in the open. A total of 95% of the plants survived the winter 2015/2016, although they suffered considerable damage. Only 33% of the terminal buds of uprights (vertical shoots) maintained their viability for regrowth in the spring. Last year's high tunnel treatment improved the winter hardiness of uprights. ‘Pilgrim’s' growth and development in the spring of 2016 were significantly faster than other cultivars. In addition, its yield potential was in a class of its own. When in average only 10% of the uprights had been induced for flowering, up to 81% of the ‘Pilgrim’ uprights were flowering. Yield results from this study should be regarded as indicative information only, as the perennial cranberry reaches its full yield potential only in later years. In 2016, only ‘Pilgrim’ had sufficient potential for harvest and yield analysis. 'Pilgrim' yielded an average of 275 g of berries per plant. Last year's high tunnel treatment increased berry yield significantly.