The invention is a method for reproducing coniferous trees by somatic embryogenesis using plant tissue culture techniques in a multistage culturing process. A suitable explant, typically the fertilized embryo excised from an immature seed, is first cultured on a medium that induces multiple early stage proembryos. These are multiplied in a second culture having reduced growth hormones. The early stage embryos may then be placed in or on a late stage proembryo development culture in order to develop very robust late stage proembryos having at least 100 cells. Culturing from this point continues in a cotyledonary embryo development medium containing an active gibberellin (GA) in an amount up to about 50 mg/L. Preferably exogenous abscisic acid (ABA) is also present in a similar amount. Concentration of GA and ABA may be reduced over time by inclusion of an adsorbent such as activated charcoal or by stepwise subcultures in which the later cultures have reduced hormone concentrations. After several weeks somatic embryos having the appearance of zygotic embryos will have formed. These may be germinated before or after storage and transplanted to soil for further growth. In addition to its use in the cotyledonary embryo development stage, GA may also be advantageously included in any of the maintenance cultures following embryo initiation. The use of GA results in larger and more robust somatic embryos and ultimately in greater germination success.
