Have you ever wanted to know whether an old fruit tree in your park is an heirloom variety?
Nowadays, this question is easier to answer than ever. All you need are leaf samples and less than $400 to reveal the exact pedigree of a single fruit tree. No more waiting around for the tree to bear some characteristic fruit (which can be a long wait with old trees in poor condition). DNA-based variety identification is available for apple, apricot, cherry, olive, peach, pear, and plum, among other species. The technology can be accessed on a fee-for-service basis, either through a credit card purchase, or through a Purchase Order award.
A mixture of historic olive varieties (UC Davis photo)
Like animals, DNA is found in plants and is unique to each species and variety. All the trees of a single fruit variety have the same genetic code, or DNA fingerprint. By cutting a sample of DNA into fragments and comparing it with other samples, it’s possible to determine whether the DNA has come from the same, or a different fruit variety. In the history of US orchards, the 19th-century was the period when most fruit varieties were originated. Far fewer varieties were planted in the 20th-century and hundreds of varieties became extinct. This is because fruit varieties or “cultivars” have been created by people, and are not naturally-occurring. Without vegetative propagation and cultivation by people, cultivars cease to exist.
Olive tree at Channel Islands National Park (NPS Photo)
DNA Testing in a National Park
Historic orchards throughout the national park system contain rare and unusual cultivars that can no longer be found in contemporary orchards. One such orchard is the historic Smugglers Cove olive orchard at Channel Islands National Park. The orchard contains several hundred trees and dates to the 1880s. CHIS staff contracted with Foundation Plant Services at UC Davis to DNA test the varieties. The cost was $265 per sample, due to the bulk quantity. Leaves were collected and express-mailed overnight to the testing lab.
The results revealed the Smugglers Cove Orchard consist of two historic varieties: “Mission” and “Redding Picholine.” Of the 105 trees tested, 27 are Mission and 76 are Redding Picholine. Two trees could not be identified and are probable seedlings.
“Mission” is the classic California olive variety introduced by Franciscan missionaries in the late 1700s. Despite its long journey to California from Morocco via Spain and Mexico, “Mission” is now one of the state’s most common varieties grown for table olives. “Redding Picholine” is more unheralded, having been imported by B. B. Redding from Europe in 1872 to serve as a hardy rootstock. The variety proved so hardy that it survived the death of other varieties grafted upon it and would sprout up to bear small olives with large pits. Over time, growers discovered these tiny olives made fragrant olive oil, but the variety had limited popularity.
Today, the Smugglers Cove Orchard is the nation’s largest extant plantation of Redding Picholine trees, where the variety was probably planted to yield fruit for olive oil. The orchard is the largest historic olive orchard in the national park system, dating from the 1880s. These results will inform the Cultural Landscape Report treatment plan.
Historic Smuggler’s Cove olive orchard at CHIS (NPS Photo)
Can’t find what you need? Contact the Park Cultural Landscapes Program via email or the program lead in your region.