The larch seed orchard studied is intended to produce interspecific hybrid seed betweenLarix sibiricaandLarix decidua.Only theL. sibiricaclone (half of the grafts) in the orchard was intended to act as the seed parent, and the sixL. deciduaclones are pollinators. The proportion of hybrid seed produced was determined using Mdh3 locus as a genetic marker. The mean percentage of hybrid seed produced by the grafts ofL. deciduawas 93, but that of the hybrid seed produced byL. sibiricawas only 18. The results can be explained by differences in flowering abundance. The grafts ofL. sibiricaproduced several times more pollen than those ofL. decidua.Contrary to the original plans,L. deciduashould be used as the seed parent andL. sibiricaonly as the pollen parent in the studied seed orchard.