Effect of CCC and daminozide on growth of silver birch container seedlings during three years after spraying

Applications of growth retardants, daminozide and CCC (chlormequatchloride), were studied in order to determine their effects on morphology and post-planting growth of silver birch (Betula pendula Roth) container seedlings. Daminozide was sprayed once (on 28 June at concentrations of 1.0 – 6.0 g l^–1) and CCC was sprayed twice (on 29 June and 27 July at concentrations of 0.5–3.0 gl^–1). Height growth, morphology of seedlings at the end of the growing season, the shoot and root growth potential the following spring and field performance during the following seasons were measured. During the first summer in the nursery, both daminozide and CCC retarded height growth,but daminozide was more effective. The effects of compounds on stem diameter during the summer of application were small. Neither of the compounds affected the field performance of seedlings. The most suitable applications for retardation of height growth, without negative effects on other morphological variables, were 4 g l^–1 (32 mg per seedling) for daminozide and 2 g l^–1 (16 mg per seedling), sprayed in two applications, for CCC.     

Use of short-day treatment in the production of Norway spruce mini-plug seedlings under plant factory conditions

Mini-plug transplant seedlings of Norway spruce have been cultivated in closed growth systems, so-called plant factories, for few years. The aim of the experiment was to define a short-day treatment (SD) that harden seedlings to sustain 3 months of cold storage, but does not have adverse effects on growth, morphology, and vitality. The seedlings were subjected to one of the following treatments: (1) 12?h photoperiod + 3 weeks duration; (2) 8?h photoperiod + 3?wk duration; (3) 12?h photoperiod + 5?wk duration; and (4) 8?h photoperiod + 5?wk SD. All the SD treatments yielded healthy seedlings that grew well after the cold storage. The frost hardiness of the seedlings improved when the photoperiod was reduced from 12 to 8?h, and when the SD duration was increased from 3 weeks to 5 weeks, but reducing the photoperiod from 12?h to 8?h caused growth reductions. The root and shoot regrowth after cold storage was highest in seedlings that had received 12?h photoperiod and 5?wk duration. However, 12?h photoperiod and 3?wk duration may be an adequate practice for nurseries that treat multiple crops in their SD facilities.     

Covering Norway spruce container seedlings with reflective shading cloth during field storage affects seedling post-planting growth

New Forests - The field storage of container seedlings is often a necessity after the seedlings have been transported from nurseries close to the regeneration area. Suboptimal storage conditions...     

The effects of calcium on stem lesions of silver birch seedlings

In this study, we tested the hypothesis that decreased liming of growth medium has a role in the increase of stem lesions and top dying caused by Phytophthora cactorum in containerized silver birch seedlings (Betula pendula) in Finnish forest nurseries. The effect of limestone dose rates on growth and the nutrient status was also monitored. An index based on severity of symptom expression was used to compare the effect of different liming treatments on P. cactorum infection. Limestone amended into the sphagnum peat growth medium increased the amount of calcium in the seedling stems. Liming did not significantly decrease the disease severity although index values in most cases decreased with the increased limestone dose rates. In general, the lesions were restricted after out‐planting and the mortality of seedlings was low. Only inoculated seedlings on which the lesions had spread around the stem in the nursery died. Phytophthora cactorum appears to be a nursery pathogen, as it did not survive under conditions present in the field. Four years after out‐planting, the tallest birches were those grown in sphagnum peat amended with the highest limestone dose of 8 kg m⁻³.     

Field performance of Scots pine (Pinus sylvestris L.) seedlings planted in disc trenched or mounded sites over an extended planting season

Economic pressures have driven an ever-widening period during which foresters use machines to plant Scots pine (Pinus sylvestris L.) seedlings. In Fennoscandia, this period has recently stretched to the entire growing season. To evaluate the performance of seedlings planted during this extended period, three experiments were carried out in Central and Northern Finland over 2 years. One-year-old and current-year seedlings were planted in mounds or disc-trenched furrows when soil temperatures were >0°C. When 1-year-old seedlings grown for spring planting and overwintered outdoors were planted after mid-June, more needles browned and growth was reduced, possibly because seedlings were oversized with respect to planting density and the volume of growth media. When current-year seedlings sown in spring were planted from July to November, those planted in late September and October grew less in later years than those planted earlier, but survival was unaffected. No large differences in field performance were found with respect to whether seedlings were planted in mounds or disc-trenched furrows. In conclusion, Scots pine seedlings can be machine planted in mounds or furrows during May and early June (later in the North) and then continued from early August until late September, provided climatic conditions in late spring and early autumn are typical and similar to those experienced in Central Finland.     

Short-day treatment during the growing period limits shoot growth and increases frost hardiness of hybrid aspen plants in the nursery

In Finland, under nursery conditions hybrid aspen may continue their shoot growth until early September. Thus, frost hardening is usually delayed. To solve this problem, we used a three-week period of short-day (SD) treatment between late July and mid-August. During autumn after frost exposure, frost hardiness (FH) was assessed three times with a stem-browning test. The re-sults showed that after SD treatment shoot growth ceased and FH increased when compared to untreated hybrid aspen. Furthermore, the height of SD-treated hybrid aspen varied much less than that of the control plants. We conclude that SD treatment in the nursery during the growing period can be used as a supplementary method for producing well-hardened and uniform hybrid aspen plants.     

Frost hardiness of nutrient-loaded two-year-old <Emphasis Type="Italic">Picea abies</Emphasis> seedlings in autumn and at the end of freezer storage

The effects of nutrient loading (NLOAD) on the frost hardening and dehardening of Picea abies (L.) Karst. seedlings were investigated under nursery conditions. Before NLOAD, second-year container seedlings were either short-day (SD) treated for 3 weeks in July or left for the natural photoperiod (CO). By mid-September, after 5 weeks of NLOAD, the fertilization of three foliar nutrient concentration levels (low = L-SD, medium = M-SD, and high = H-SD) for the SD-treated seedlings and one (medium = M-CO) for the CO-seedlings was completed. The NLOAD resulted in foliar nitrogen concentration 10.6, 16.1, 22.3, and 17.5 g kg⁻¹ for L-SD, M-SD, H-SD and M-CO seedlings, respectively. The NLOAD had no effects on the morphology or dry mass variables of the seedlings, while SD-treatment reduced the dry mass of shoots, but not that of roots. The frost hardiness (FH) of different batches of the seedlings was assessed by the visual scoring of damage in their needles, stems and buds after their controlled exposure to freezing during frost hardening and dehardening. The low nutrient concentration in the SD-treated seedlings (L-SD seedlings) resulted in poor FH, to an even lower extent than that of the M-CO seedlings. The NLOAD did not affect the dehardening of the seedlings at the end of the freezer storage in the following spring.