Swan Hill Nurseries

Additional Information about the Swan Hill Olive ®

Fruit

The European Olive cultivar "Swan Hill" (Olea europeae cv. "Swan Hill®"), as a propagated scion sold by Swan Hill Nurseries, LLC may produce some flowers. Due to a genetic anomaly which renders the male portion of the flower (anther) defective, little (less than 1% compared to flowering olive varieties) or no pollen is released. The Swan Hill Olive®, as produced by Swan Hill Nurseries, LLC, with some exceptions, produces no mature, black, pitted fruit.

When the Swan Hill Olive® flowers some swelling of the female portion of the flower (the pistal) may occur, giving the impression that the production of the mature black fruit has been initiated. This enlargement is due to a form of non-sexual reproduction called parthenocarpy. Parthenocarpy is the formation of "fruit" without pollination. In the Swan Hill Olive® this results in a type of "false pregnancy", where these false fruit ("shot berries") will abort, dry-up and abscise (fall from the tree). Since these "shot berries" are mostly water, they dry up rapidly and quickly disappear, leaving little or no trace.

Occasionally, fruit with a seed can be found, but these are also "imperfect" fruit and will dry up and fall from the tree before they mature into a black olive. In the warmer drier conditions of Arizona, Nevada and Southern California, most if not all of these false fruit will fall from the tree by the first of July and we have rarely seen any after the middle of July. Warmer drier springs and early summer conditions will hasten the shed of these false fruit. But, in the Northern California, extending from approximately San Jose North, cooler and moisture conditions may cause the flowering of the Swan Hill Olive® to be delayed until as late as the first of July and the "shot berries" and some seeded fruit may persist into August and September. This condition varies from tree to tree and location to location. We have never observed more than a handful of fruit persist to pitted/black fruit stage on even the most mature swan hill olives® growing in northern California.

Swan Hill Nurseries, LLC has distributed more than 120,000 Swan Hill Olives® to landscapes in five Western States, as a non-fruiting/non-pollinating cultivar since 1986. This is the only tree we grow and Swan Hill Nurseries, LLC would not be in production if the Swan Hill Olive® were it not truly a non-fruiting/non-pollinating cultivar. There is no unsightly staining of sidewalks, pool decks, streets, water features, and, for allergy sufferers, no irritating pollen.

Rootstock

On the rare occasions when mature or large fruit that appear on Swan Hill Olive®, trees they are invariably associated with sucker growth from the 'Oblonga' rootstock. The Swan Hill Olive® is grafted to the "Oblonga" rootstock to protect the tree from a common, potentially fatal, soil-borne disease, Verticillium Wilt. The 'Oblonga' rootstock does produce fruit and will release pollen. Please advise your customers to remove all branches arising from near the soil line or below ("suckers"), when and if they appear. These suckers will have a different trunk color and texture. Suckers can grow quite rapidly and should be removed as soon as they are observed.