Cultivation of Sweet Cherry under Rain Covers

'Burlat', 'Earlise', 'Samba', 'Souvenir des Charmes' and clone M sweet cherry (Prunus avium L.) trees, all with early ripening, large and dark red-black fruit, were grown at 3.8 x 1.75 in under a complete cover from rain in April-May 2004 and 2005 at the Klein-Altendorf Research Station near Bonn, Germany. The results included: 1) Flowering was 6 to 13 days earlier and fruit ripened 12 to 19 days earlier than those from uncovered control trees, indicating a shorter or enhanced fruit development and maturation. 2) The cover proved insufficient for frost protection at night, despite increased daytime air and soil temperatures (by up to 15 degrees and 5 degrees C, respectively). Trickle irrigation was used to overcome soil moisture loss under covers from rain. 3) Cherry leaves grown under the cover contained sufficient chlorophyll for photosynthesis. 4) Three-year-old trees on dwarfing 'GiSelA 5' rootstock under the cover were more vigorous than those without cover and produced 3 to 4.5 kg of fruit per tree in 2004 with less cracking. Three of the five cultivars had an average fruit mass of 9 to 15 g, equivalent to 25 to 33 mm fruit diameter. 5) The cover had no adverse effect on fruit colouration. Cherry fruit grown under cover were slightly smaller, softer, attractively coloured and tasted better due to increases in both sugar and acidity with sugar:acid ratios of 25:1 to 30:1. 6) There was essentially no crop under the cover in spring 2005, possibly due to overheating at fruit set in April/May despite open vents.