Transplanting recently germinated seedlings into conetainers
Plants in the nursery are propagated from either seed or cuttings collected within the Lake Mead NRA, or on other public lands in the area in order to supply local site appropriate genetics. Seed is then extracted, dried, cleaned and weighed at the nursery. A computer database is used to record and track seeds.
Once processed, seed lots are stored in a special seed room, insulated and air-conditioned to protect against heat in the summer, and sealed against rodents. The nursery has plans to build a strawbale seed storage facility in the near future. This super insulated structure will enclose a coldroom that will keep seeds at about 4 ºC, much better than the maximum of 27 ºC that is currently achieved (when temperatures outside climb above 45 ºC).
Despite the approximately room temperature storage that has been the norm to date, viability of seeds in the collection has remained relatively good. Germination rates of around 50% have been recorded for seed lots as much as 14 years old. This is probably because the seeds of desert plants are adapted to enduring high temperatures and long dormancies due to the extreme nature of the environment in which they live. That said however, improved storage will likely maintain the viability of seed for even longer.
Given the infrequency of good seed years in the desert, the ability to store seeds for extended periods is particularly important. Fortunately 2005 was an uncommonly good year, with seed of over 40 species collected. In several cases these were either new species not in the collection, or replenished stock which had been depleted. Even for those species well represented in the collection, fresh seed is useful.
Once a production order is finalized, seeds are pulled from the collection, pretreated (if necessary) to break dormancy, sown, and allowed to germinate. When ready they are transplanted to larger conainers, and eventually achieve a size where they can be moved out of the greenhouse and be kept in the compound. Time outside is particularly important to produce plants that are adapted to the natural climate, and are properly hardened off when planting time arrives.