Seed soak-sorting prior to sowing affects the size and quality of 1.5-year-old containerized <i>Picea abies</i> seedlings

We studied the effect of soak-sorting Norway spruce (Picea abies (L.) H. Karst.) seeds on emer- gence, development and quality of container seedlings in two commercial seed lots. The seeds, separated by soaking into bottom and surface fractions, were sown in June, and the seedlings were grownduringtwogrowingseasonsundertypicalFinnishnurseryconditions. Thefirstsummer seedlings were grown in a greenhouse and outdoors for the second, full growing season. All sunkenseedswerefullandviabl eaccordingtoradiography , whereasthefloatingseedscontained 2%and 13% larvae-filledand 8% and 1 1% anatomicallyimmatureseeds, dependingontheseed lot. Seedlings grown from the bottom fraction seed emerged 2.5-3.5 days earlier than seedlings of storage dry (i.e. control) seed. Height, diameter, and shoot and root dry mass of the seedlings wereaf fectedbysoakingafterboththefirstandsecondgrowingseasons. Thelar gestseedlings originated from the bottom fraction. The proportion of saleable seedlings was four percentage points higher in the bottom fraction than in the other seedlings. The effects of soaking found in this study are more notable than as previously reported for Norway spruce seedlings. This suggests that soaking and soak-sorting may be most useful when the growing conditions are stressful, i.e. when seeds are sown in summer rather than 1-year-old seedling crops sown in spring under the climate conditions typical of Finland.