Containerized culture of eastern white pine seedlings

Nursery production of white pine seedlings that are suitable for outplanting requires 2 years. Greenhouse containerized culture of white pine seedlings accomplishes the same goal in less than 1 year. In this study, white pine seedlings were grown for 7 and 11 months in the following greenhouse environments: 1. 24-hour photoperiod, enriched CO₂, 2. 24-hour photoperiod, ambient CO₂, 3. natural photoperiod, enriched CO₂, and 4. natural photoperiod, ambient CO₂, All seedlings received maintenance fertilization and one half received foliar topdressing. All seedlings were inoculated with Pisolithus tinctorius spores. Seedling height, root collar diameter, fresh top and root weights, and dry top and root weights were recorded. Mycorrhizae formation was noted. Significantly greater root collar diameter and biomass resulted from the 24-hour photoperiod and enriched CO₂ treatments; however, these same treatments reduced height growth. Seedlings receiving maintenance fertilizer plus topdressing had greater top weights. Significantly greater height, root collar diameter, root weight, and root/shoot ratio were obtained using only the maintenance fertilizer. The environment which resulted in the largest greenhouse-grown seedlings was the 24-hour photoperiod, enriched CO₂ level, and maintenance fertilizer. Seven-month- old containerized seedlings and 2-0 nursery bare-root seedlings were outplanted. Survival, height, new growth, root collar diameter, and competing vegetation were measured during the first and second season. Although the 2-year nursery-grown seedlings maintained greater growth after outplanting than the containerized seedlings, their survival was significantly lower. Natural photoperiod, ambient CO₂ greenhouse treatment seedlings had the highest survival, while seedlings grown under the 24-hour photoperiod, ambient CO₂ treatments had the greatest height and root collar diameter growth.