Previous studies revealed that in terms of the stem height growth, containerised seedlings with an average height:diameter ratio(HDR)of ca. 60 are superior to conventional bare-root seedlings and containerised seedlings with an average HDR of ca. 100 are inferior to conventional bare-root seedlings. In this study, we focused on the correlation between the stem growth and HDR in individual seedlings. We measured the stem growth of 2-year-old containerised seedlings and 3-year-old conventional bare-root seedlings for four growth seasons. In each of the growth seasons, HDR showed a negative correlation with stem height growth rate and a positive correlation with the stem radial growth rate of an individual seedling; the strongest correlation was observed in the first and second growth seasons. Therefore, the seedling with a high HDR allocated resources to stem radial growth rather than to height growth. Regarding the stem height growth, we analysed the sequential data for four growth seasons using a linear mixed effects model. HDR showed a negative correlation with the stem height growth. In conclusion, high HDR had negative effects on not only the relative height growth rate but also on the actual height growth.

The nursing condition of a containerized seedling results in a large shoot-root ratio, which could cause it severe water stress after planting. The present study aimed to clarify the relationship between the form of a seedling and the severity of water stress after planting, which was the basis of evaluation basis for the proper planting of seedlings. We planted the containerized Cryptomeria japonica seedlings during late August and early September. The severity of water stress was evaluated by transpiration rate. The taller seedling tended to have a higher H/D ratio (height to diameter ratio) and higher shoot to fine-root ratio. The transpiration rate of the seedling with a higher shoot to fine-root ratio tended to be lower. The seedling with a lower transpiration rate tended to have a slower root growth after planting. We suggested that the taller seedlings may suffer severer water stress after planting and need more time to establish a balance between leaf mass and fine root mass after planting

We investigated the early performance of current and one-year-old containerized sugi cuttings planted in late summer (September) and compared it with that of current-year bare-root cuttings. The leaf water potential of bare-root cuttings declined abruptly after the planting, and remained lower than that of the containerized cuttings for the following one month, but this water stress did not result in tree death. One-year-old containerized cuttings had the tallest tree height at planting, followed by current-year containerized cuttings and bare-root cuttings. However, the height growth during the second growing season was largest for bare-root cuttings, which resulted in no significant difference in tree heights at one year after planting among the cutting types. The difference in the dry matter allocation to above- and below-ground parts among the cutting types observed at planting also disappeared one year after the planting. At the end of the planting year, we observed a larger incidence of inclination damage for one-year-old containerized cuttings, and of the symptom of wilting in apical shoots for bare-root cuttings. However, these differences also disappeared one year after the planting. We concluded that the superiority of the containerized cuttings in summer planting was limited, at least under the moderate/light drought conditions for the case of the present study, though the containerized cutting implied more tolerance to dryer conditions.

One-year-old container seedlings of Japanese larch (Larix kaempferi) sown in containers were planted every month from May to October 2014 to evaluate the survival rate, growth and ecophysiological properties. Two-year-old bare-root seedlings were planted in May as a reference. When seedlings were planted before budburst in May, the growth of shoot and root, photosynthetic rate and stomatal conductance of container seedlings were higher than those of bare-root seedlings, though there was no difference in the height or diameter between container and bare-root seedlings in the second year. Container seedlings planted from June to August had fewer roots with higher fine root electrolyte leakage, water potential at turgor loss point and foliage/root ratio. Container seedlings planted in June and July experienced 62 and 22% survival in the current year, respectively. The low survival was caused by the low drought tolerance of seedlings and low rainfall in the planted period. Container seedlings planted in September and October showed a high drought tolerance and survival rate. The results suggest that the planting period can be extended to two months in the fall by using container seedlings without increasing mortality, but the same may not be true in summer.

To evaluate the optimum planting date for containerized seedlings of Larix kaempferi, we compared the survival rate and shoot and root growth of seedlings planted monthly from May through November. The planting date affected the growth in both the planting year and the following year. The survival rate one month after planting was at least 97%. However, root elongation remarkably decreased when seedlings were planted in October or later, because of the low ground temperature. In the planting year, shoot elongation was observed only in seedlings planted in June or earlier, and their shoot elongation rate peaked one month after the peak of the root elongation rate. Seedlings with the earlier planting dates yielded the greater root weight at the end of the planting year, which resulted in the greater shoot elongation in the following year. The difference in tree height, which existed at the end of the planting year, was still apparent at the end of the following year. Our results thus indicate that Larix kaempferi containerized seedlings should be planted until August, though seedling survival one month after planting was independent of the planting date.

We compared the survival and growth between containerized (CT) and bare-root (BR) seedlings of Hinoki (Chamaecyparis obtusa) planted at different seasons (summer: August 2013, autumn: October 2013 and spring: May 2014) at Sanko national forest in Okayama Prefecture. Seedling survival rate was significantly higher in CT than BR and it was consistent with all three planting seasons. Survival rate for summer planted seedlings was much higher in CT than in BR (CT, 90%; BR, 57%). Growth rate in stem diameter showed no significant difference between two stock types for summer planted seedlings, whereas it was significantly lower in CT than BR for autumn and spring planted seedlings. Difference of height growth between the stock types was insignificant for seedlings planted in autumn and spring meanwhile CT showed significantly higher height growth than BR for summer planted seedlings. Planting period for Hinoki can be extended using CT including summer which was not suitable for planting in BR.