Catching Up With Conservation: Florida Ziziphus

In May, the annual harvest of Florida ziziphus fruit was completed. Florida Ziziphus, Ziziphus celata, is a very rare shrub in the buckthorn (Rhamnaceae) family, found only in a handful of populations in Polk and Highlands County. It was originally described from a 1949 herbarium specimen and presumed extinct until it was rediscovered in 1987. Upon its rediscovery, Archbold Biological Station and Bok Tower Gardens began a collaboration to learn how to conserve the species.

They learned that although the plants in these wild populations profusely flowered and attracted an abundance of pollinators, no fruits were produced. Research showed that this species is an ‘obligate outcrosser,’only able to reproduce with other individuals that are genetically different (those of different genotypes). Unfortunately, each of the plants in any one population were either clones of each other or too closely related for reproduction to take place.

The good news was that the different populations contained different genotypes. In 1987, the Rare Plant Conservation Program (RPCP) at Bok Tower Gardens began collecting root cuttings to produce clones from each of these populations to bring into the National Collection beds at the Gardens, and thereby bring the different genotypes together. The plants gradually grew to reproductive size, and in 1994, the plants were able to cross pollinate and the very first crop of fruit ever known was produced, right in the National Collection Beds. And fruit has been produced in the beds every year since.

Since 1994, there have been an average of 3,712 fruits produced in the beds. 2023 was a good year, with 6,841 fruits produced! Harvesting is done by picking fresh, ripe fruits from each plant daily, and placing them into protective drying racks, which were specially built by our volunteer Joe Fabach. Once the pulp is dry, the fruits are counted, sorted, dried further in a seed desiccator to 30% relative humidity, and packaged, keeping them separate by maternal parent. The packages are placed in cold storage for preservation for the future.

The annual harvest of Ziziphus fruits help produce seedlings that are used to create new populations onto protected lands, and help preserve this very rare species into the future.

Article written by Cheryl Peterson, Conservation Manager.

Posted in