It’s not imaginary; the most common tree at Ramat Hanadiv is mock privet

Dr. Racheli Schwartz-Tzachor

Mock privet (Phillyrea latifolia), which belongs to the olive family (Oleaceae), is the most common species of tree growing in the Nature Park at Ramat Hanadiv. It is also very common on Mt. Carmel, in the Galilee and throughout the entire Mediterranean region of Israel. Nevertheless, most nature lovers and hikers are not familiar with it.

You will probably ask why people aren’t familiar with it. It turns out that over the years this plant has suffered bad publicity. For some reason it has not been chosen as a research subject, or as a model for drawing and no poems or stories have been written about it. Thus it remained anonymous despite its considerable presence in nature in Israel. Furthermore, nature lovers tended to confuse it with a much more familiar and well-known tree, the Palestine oak (Quercus calliprinos). How then is it possible to distinguish between them? It’s easy in the spring and summer, when the fruit ripen, since mock privet has succulent purple fruit while the fruit of the Palestine oak are acorns, of course. In the absence of fruit we must examine how the leaves are arranged; mock privet has opposite leaves while the Palestine oak has alternate leaves.

At Ramat Hanadiv we chose to bring mock privet out of its anonymity, devote time and resources to it, and make it the subject of a long-term

study. We were surprised to discover that this is a tree with extraordinary sexuality! About half of the trees are monoecious, that is, they have bisexual flowers that contain both male sex organs (stamens) and female sex organs (ovary, style and stigma), while the other half of the trees have male flowers. In fact, these male flowers also contain female sex organs but the female part is sterile. Therefore, from a functional point of view, they function as male trees whose flowers contribute pollen and they do not produce fruit. Another interesting phenomenon revealed by the study was that mock privet hosts a gall-forming midge belonging to the Cecidomyiidae family. The female gall midge lays eggs inside the ovaries of the mock privet flower using its needle-like ovipositor.

The flower’s ovary develops into a polygon-shaped gall in which the gall-midge larva develops. The larva grows and eventually pupates inside the gall. When the mock privet flowers during the following season, the pupa breaks out of the gall using specialised protuberances. The adult gall midge emerges from the pupa, flies away, and finds a male or female in order to mate; the female searches for mock privet flowers in order to lay eggs in their ovaries, and so on.

The study on mock privet at Ramat Hanadiv lasted for about a decade, from 1993 to 2003, with a major focus on the effect of cattle grazing on mock privet trees, as cattle grazing has been implemented as part of a management regime to prevent fires and promote high diversity of the herbaceous vegetation.

The attached files here on Ramat Hanadiv’s website include detailed publications of the results of the long-term study which helped to bring mock privet out of its anonymity in Israel.

Mock privet fruit

Galled fruit

Ripe fruit

קישורים נוספים

Phillyrea latifolia, poster for Medecos conference 2004
Phillyrea latifolia, poster for Medecos conference 2004
The effect of management treatments on pheno-morphological traits of Phillyrea latifolia L.