Note: Recalcitrant seeds are non-storable, when ordering tree species noted as “recalcitrants”please make sure that you order them during the collection season (find seed collection calendar at seed documents and resources section) and when delivered to you please plant immediately .

TFS main collections comprised of orthodox seeds (about 90%), and 5 % intermediate seeds and other 5% recalcitrant. Orthodox seeds are those seeds that are desiccation tolerant i.e. their moisture content can be lowered (dried) and seed can survive drying to 10-15% eRH (3-7 % mc). They include most of available species in Tanzania e.g All acacias. On other hand recalcitrant are those species seeds that desiccation intolerants i.e. Seeds die when dried below a relatively high moisture content. High critical (lowest safe) moisture content which also varies with species. In this lists includea cacao, allanblackia  spp, Eriobotrya japonica, Maesopsis eminii, Polyalthia longifolia, Prunus Africana, Sorindeia madagascariensis, 
Syzygium cordatum, Syzygium cumini, Syzygium guineense, Trichilia emetica and Uapaca kirkiana among others. These also can not tolerate freezing storages. 
Intermediate seeds are subset of Orthodox and tolerate drying to around 40-50% eRH (around 8% mc) and are often sensitive to -20°C storage. Species that are in this group includes Gmelina arborea, Khaya anthotheca (when harvested at maturity with proper drying they can behave more orthodox like), Dovyaris caffra, Azadirachta indica and Melia azedarach.