WHEN a load of 800,000 evergreen seedlings leaves the Port of Tacoma in early May, the Weyerhaeuser Company will take its latest step in an experimental effort to assist Russian foresters in growing forests in the Russian Far East. Weyerhaeuser's first large-scale shipment of seedlings will sail in early May for the region in eight 20 ft refrigerated containers aboard the Anatoliy Kolesnichenko. The vessel is the third Russian ship to call at the Port of Tacoma as part of a renewed service offered by Far Eastern Shipping Company (FESCO), Russia's largest international shipping line. Beginning last December, FESCO launched a trial service between Tacoma and Russian ports such as Vladivostok and Magadan. FESCO's most recent ship call to Tacoma came March 30 when the Kapitan Man took on a shipment of cars, tractors, dental equipment, and frozen and canned foods. The shipments of seedlings will be accompanied by a similar mix of cargo, including 20 Caterpillar construction tractors plus five large earth-moving vehicles. ''We are still very optimistic that these monthly ship calls will eventually become regular service between Tacoma and Vladivostok,'' said Alexander Buriy, a FESCO director assigned to the FESCO agency in Seattle. ''Weyerhaeuser's programme adds a very important customer to this emerging service. ''We are seeing increasing numbers of American companies exploring business in Russia, and we want to do all we can to provide a competitive trade route,'' said Jack Fabulich, president of the Port of Tacoma Commission. The Port of Tacoma has maintained strong ties with Russia ever since it established a sister port relationship with Vladivostok in November 1991. Weyerhaeuser has been working for several years to nurture a joint venture in Russia. Mr Bob Lowery, the company's international reforestation project manager, said the hopes for such a venture remain very much alive despite Russia's continuing economic and political struggles. ''We are optimistic, but the time frame for the joint venture is difficult to know,'' he said. ''Starting from seeds collected in the Khabarovsk area, these seedlings have been growing in Weyerhaeuser's western Washington nurseries. The seeds are now ready to go, and at this point we are moving ahead.'' Weyerhaeuser is the world's largest single producer of softwood lumber and market pulp. The company's effort in Russia is aimed at establishing reforestation as a new and permanent activity in conjunction with a Russian operation that currently includes logging, manufacturing and exports to other Asian markets. Mr Lowery said if the joint venture succeeds the plan calls for planting 2 million seedlings per year over the next four years with an eventual goal of planting 10 million per year.