American-born Sara Perzley graduated from the RBG Edinburgh. She is one of the 2013-4 scholars of horticulture at the Gardens, supported by the British Friends of the JBG. Here she writes about her work with rare plants.
Many visitors to the Jerusalem Botanical Gardens (JBG) have strolled past the beds of rare and endangered plants in the garden. What they may not have realized, however, is that the contents of these beds represent only a small fraction of the Gardens’ total collection of rare plants. While it would be ideal to have the entire collection on public display, practical considerations prevent this, and most of the rare plants are kept behind the scenes in the propagation nursery, visible to guided groups only.
A large proportion of rare Israeli native plants, and Israeli native plants in general, are annuals, completing their entire lifecycle over the course of a year. This makes evolutionary sense in a climate with a hot, bone-dry summer. Instead of developing adaptations such as water storage organs or the ability to go dormant for a season, nimble annuals simply begin growing after the autumn and winter rains, and quickly flower and set seed by late spring or early summer. Although the plants themselves cannot survive through the dry season, their seeds can, and are ready to start the cycle over again in the autumn.
While this is a streamlined, efficient strategy from the point of view of the annuals, it makes for quite a lot of work for whoever is looking after the collection of rare plants at the JBG. At the moment, that would be me! I have spent my first several months at the Gardens sowing seeds, pricking out seedlings into larger containers, and of course, documenting the entire process in the plant records system.
As there is not enough space or time to plant all of the rare annuals out in the Gardens, most are kept to grow in buckets in the nursery, where they can be monitored and where their seeds can be easily collected to be sown again next autumn. The collection serves as a living gene bank for rare species, and occasionally some of the plants grown in the nursery are given to nature reserves to bolster or replace populations that have diminished or been lost.
One of the important records kept about the rare plant collection involves the percentage of seeds that germinate from each species sown. Many of the rare annuals germinate easily and quickly, approaching 100% germination, but others are more tricky, with less than 1% germination. For some species, germination can be aided by using techniques such as soaking the seeds in water before sowing or chilling them in a refrigerator. Data on how to propagate rare plants, most of which are not cultivated in gardens, can be difficult to impossible to find, so it is important for botanic gardens to keep their own records and notes for the future.
So far this year, a total of 127 rare species have been sown, spanning the alphabetical gamut from Acinos rotundifolius to Ziziphora tenuioir. Most of these are Israeli native plants listed in the Red Data Book: Endangered Plants of Israel, a catalogue of the 413 plant species that are most threatened in this country. However, the collection also includes a few rare plants collected in other parts of the world by JBG scientists and colleagues abroad. More rare seeds will be sown in February, from plants that prefer warmer growing temperatures and would not have been happy germinating during the middle of a Jerusalem winter, especially one that included a major winter snowstorm!