The rapid establishment of seedlings in forest regeneration or afforestation sites after planting is a prerequisite for successful reforestation. The relationship between the quality of the seedling material and their growth and survival after outplanting has been recognized for decades. Despite the existence of a substantial amount of information on how to produce high-quality seedlings, there is still a need to develop practices that can be used in nurseries and at planting sites to be able to produce well-growing forest stands in ever-changing environments. This Special Issue of Forests is focused on seedling quality and how it can be manipulated in a nursery as well as how the quality of the seedlings affects their field performance after planting.

For spring plantings, conifer seedlings are usually packed in closed cardboard boxes and freezer stored over winter. Additionally, seedlings are increasingly being stored in cardboard boxes in spring, summer, and autumn plantings in Finland. The aim of this study was to determine the maximum safe duration for the field storage of Norway spruce (Picea abies (L.) Karst.) and Scots pine (Pinus sylvestris L.) container seedlings in closed cardboard boxes for different planting times (dates) in Nordic boreal conditions. In the first experiment, Norway spruce seedlings (85-cm³ peat plugs) were packed in cardboard boxes in August, September, or October, and, in the second experiment, in the middle of May. In the third Scots pine experiment, mini seedlings (30-cm³ peat plugs) were packed in May. In each experiment, the seedlings were stored in closed cardboard boxes in a nursery for one, three, seven, 14, and 21 days. The control seedlings were stored in open storage in the nursery. After storage, the seedlings were planted in a field. In all of the experiments, increased closed-box storage reduced the maximum photochemical yield of photosystem II (F_v/F_m) in the needles, and reduced root growth after planting. The frost hardiness was weakened in the Norway spruce seedlings that were stored in closed boxes for 21 days in August and October. In the spring experiments, prolonged storage increased the mortality of seedlings. Mortality rates were high in the autumn experiment due to the exceptionally warm and dry weather. Our conclusions, being based on the short term effects of field storage, are that conifer seedlings can be stored in closed boxes for only three days in August and about a week in September, October, and spring.