Influence of temporary covers on the growth of nursery tree seedlings

Seeds of Fagus sylvatica, Prunus avium and Acer pseudoplatanus were sown on 10 May and covered with four materials: white polyethylene, white polyprop ylene, yellow net or green net for 90 d to study the effect of a temporary covering on soil and air temperature, increment in dry weight, and root cel lular diameter of nursery tree seedlings in a northern climate. Root collar diameter, height and dry weight of covered seedlings were compared with th ose of uncovered control seedlings at the end of growing season. The increa se in soil and air temperature under white polyethylene, white polypropylen e and yellow net and the decrease in soil temperature under the green net i nfluenced the growth of F. sylvatica and P. avium seedlings. Dry weight, as well as root collar diameter and height, was increased under the coverings increasing temperature. A. pseudoplatanus responded less to temperature, b ut increased dry weight and root collar diameter when cultivated under whit e polypropylene and green net. Hence temporary coverings can be used to imp rove the quality of seedlings grown in a northern climate.