Worldwide, conifer growers work hard every season to supply the best quality seedlings for reforestation or landscaping industry. In the last decades, greenhouse and nursery techniques of growing conifers are developing constantly, both for family nurseries and large companies.  Each conifer species or variety has its own cultivation technology that starts with seed sowing, grafting or propagation from cuttings.

At Ferma de Brazi tree nursery, in Albac, one of the few Romanian conifer nurseries, bare-root coniferous species are produced on a large scale mainly in wooden and metalic structure polyethylene greenhouses due to numerous technical and economic considerations. The technical advantages of this method allows a crop rotation every year both in greenhouses and outside nurseries and provides a large number of seedlings/m² which achieve dimensional and morphological parameters for use on reforestation sites.

Bare-root conifer seedling production in greenhouses and nurseries at Ferma de Brazi, Albac, Romania.

 Photo credit: Sorin T. Șchiop

Conifer growing technology in greenhouses involves sowing the seeds in rills after a previous preparing of a soil layer consisting of decomposed litter, spruce humus and beech humus (Milescu, 2006). Radu et al. (1994) listed a number of seed treatments applied before seed germination, consisting in keeping them in cold water for 24-48 hours or snow for 15-30 days; another method of enhancing germination is cold stratification for 3-5 weeks, at 2-5^oC (needed for most Abies, Cedar and Pinus species). Other recommendations include an optimum seeding depth of 0.5-2 cm, correlated with seed size, and rill covering using sieved conifer humus mixed with sand, on a ratio of 3:1.  Seed germination generally occurs after about 2-3 weeks, depending on species, irrigation frequency, temperature and humidity inside the greenhouse, while the new plantlet is identified by radicle, hypocotyl and several bent cotyledons which remain attached on the seed in the first days of development.

             Growth stages of Norway spruce seedlings. Photo credit: Sorin T. Șchiop

Due to the shortcomings regarding the controlled conditions in polyethylene greenhouses, mean temperature, light intensity and humidity may oscillate between day and night. Previous studies showed that a mean temperature between 18-21°C is optimum for conifer seeds germination, while during the first months of greenhouse growth, day/night temperatures should be around 20-24°C and 13-26°C respectively (Matthews, 1971; Tinus and McDonald, 1979). Conifers develop a photoperiod response to the light exposure; during the first stages of seedling growth they need a long day period while at the end of vegetation period a reduction of light duration is needed (Eng, 1991). Soil moisture plays also an important role in seedling germination and growth and it is influenced by the watering method used in practice. Most of the small greenhouses are watered by hand using shower-devices powered by water-tanks positioned on the top parts of the greenhouse, but lately sprinkle systems and automatic controlled ones are widely used.

   Irrigation systems in greenhouse and nursery. Photo credit: Sorin T. Șchiop

Seedling adaptation to environmental conditions plays a major role in the success of reforestation work on planted sites, while outside growth in nurseries ensures higher chances for plants survival. Conifer seedling rearing in open field can be achieved using two technical methods which are commonly used in Romania. The first, direct sowing of seeds in nurseries requires a high amount of seeds and a prior soil preparation but often with poor results (Holonec, 2003). Greenhouse-nursery system, consisting of indoor sowing and growing the seedlings during one year and later lining out for two years in open-air is used today on a large scale for most of the conifer species. During technological steps of  seedling production in nurseries, a special attention should be focused on choosing an appropiate location according to species requirements regarding light and heat, while soil preparing for deep loosening and the application of fertilizer doses will ensure proper conditions for seedling adaptation to the new conditions. The main problems that may be encountered are related to high differences in temperature between growth periods, causing frost heaving of young plants, pests or weed installation.

         Spring, fall and winter season at Ferma de Brazi tree nursery, Albac, Romania. Photo credit: Sorin T. Șchiop

In conclusion, the traditional method of conifer seedling production is still alive and  used with success in some parts of Europe, being a feasible alternative to the automated containerized production, using local, microclimate  conditions, and giving “noble value” to the lands in the mountainous countryside.

For more data about Ferma de Brazi tree nursery you can visit www.puieti-forestieri.ro or Facebook page https://www.facebook.com/profile.php?id=100009103964274.

About the Author:

Sorin T. Șchiop

Forestry engineer working in a Romanian forest district. He has a PhD in Genetics and Plant Breeding, with most of the research conducted at the Institute for Plant Molecular and Cellular Biology, Polytechnic University of Valencia, Spain. His expertise includes genetic diversity and biochemical response of Norway spruce seedlings to salt and drought stress, greenhouse and nursery production of conifer seedlings (seed and grafting), forestry management.

Cover photo: Conifer seedling greenhouse in Albac, Romania. Photo credit: Sorin T. Șchiop

References:

1. Eng RYN (1991). Temperature, nutrition, light and moisture regimes used at Red Rock Research Station to produce container 1+0 spruce seedlings. Research Report RR 91004-PG, Ministry of Forests, Victoria.
2. Holonec L (2003). Protecţia integrată a arboretelor din judeţul Cluj prin tehnologii moderne şi acţiuni fitosanitare economice, ecologice. Teză de doctorat. USAMV Cluj- Napoca.
3. Matthews RG (1971). Container seedling production: a provisional manual. Can. For. Serv., Ottawa, Ont. Inf Rep BC-X-58.
4. Milescu I (2006). Cartea Silvicultorului. Ed. Universităţii Suceava, Suceava.
5. Radu S, Contescu L, Herţa I, Burza E, Roşca T (1994). Pepiniere- Metode şi procedee pentru cultura în pepinieră a principalelor specii forestiere şi ornamentale. Institutul de Cercetări şi Amenajări Silvice, Bucureşti.
6. Tinus RW, McDonald SE (1979). How to grow tree seedlings in containers in greenhouses. US. Dep. Agric. For. Serv., Rocky Mtn. For. Range Exp. Sta., Fort Collins, Col Gen Tech Rep RM-60.