Duration Limits on Field Storage in Closed Cardboard Boxes before Planting of Norway Spruce and Scots Pine Container Seedlings in Different Planting Seasons

Jaana Luoranen,Heli Peltola,Marja Poteri,Johanna Riikonen,Laura Pikkarainen

doi:10.3390/f10121126

Jaana Luoranen, Heli Peltola + Show 3 more

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https://doi.org/10.3390/f10121126

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Abstract

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 (Fv/Fm) 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.

Highlights

In the Nordic countries, the planting season for conifer tree species has been extended to cover the entire period of unfrozen soil, from spring to late autumn
Scots pine seedlings that were stored for or days the seedlings in open storage, the height growth reduced after the 14- and 21-day storage grew less, and the growth reduction was greater in the seedlings that were stored in boxes than in periods in both methods (Figure 8a)
It can be concluded that even a few days in dark conditions in closed boxes weakens the vitality of the needles, root growth after planting and the frost hardening (FH) of the seedlings in autumn plantings

Summary

Introduction

In the Nordic countries, the planting season for conifer tree species has been extended to cover the entire period of unfrozen soil, from spring to late autumn. In Finland, for example, frozen or open-stored, dormant container seedlings of Norway spruce (Picea abies (L.) Karst.) are recommended for planting between May and the middle of June. Actively-growing Norway spruce seedlings are suggested to be planted between June and the end of July. Forests 2019, 10, 1126 it is suggested that container seedlings are only planted in spring or early summer due to their growth rhythm and growing conditions in their typical planting sites in Nordic countries [3,4,5]. To the Nordic countries, summer plantings in July and August are performed for different pine and spruce species in North America [6,7]. The extension of the planting season is a major prerequisite for enhancing the cost-competitiveness and facilitating the growth of the Nordic mechanized tree planting business [8]

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