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| Category: Tree |
| Family: Myrtaceae (Myrtles) |
| Origin: Australia (Australasia) |
| Evergreen: Yes |
| Red/Purple Foliage: Yes |
| Flower Color: Creamy White |
| Bloomtime: Spring/Summer |
| Synonyms: [Syzygium paniculatum, Hort., Eugenia myrtifolia] |
| Height: 25-40 feet |
| Width: 10-20 feet |
| Exposure: Sun or Shade |
| Deer Tolerant: Yes |
| Irrigation (H2O Info): Medium Water Needs |
| Winter Hardiness: 25-30° F |
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Syzygium australe (Eugenia) - An upright tree that with age can reach 30-50+ feet tall but is most often maintained as a medium to large screening shrub or formally kept even lower as a hedge. The new foliage, produced nearly year round, is bronze-red then maturing to a 1 to 3 inch by 1/2 to 1 inch wide glossy green leaf. Creamy white brush like flowers appear in the late spring to early summer in terminal clusters and then produce edible rose-purple fruit. Plant in sun or part shade and water occasionally to moderately. Hardy without damage to around 25° F and stem hardy to short duration temperatures to about 20° F, though even older plants can perish if temperatures drop much below this or duration is too long. Can be a useful plant in coastal areas given some protection from direct ocean winds (Hoyt Zone 3). This plant is one of the most common of hedges in Santa Barbara and elsewhere throughout Southern California, though huge tree specimens also exist in local parks - a tree at the historical Stow House in Goleta, CA exceeds 70 feet in height and is now listed in largest of its kind on the California Big Tree Registry. In May 1988 a serious pest, the psyllid Trioza eugeniae (a small winged insect about the size of an aphid) was found near Inglewood in Los Angeles County and by the end of the year had spread to Orange County, Ventura, Santa Barbara, San Luis Obispo and San Diego Counties and by the following year was found in several bay area counties. The most obvious damage that this pest caused was blister-like pits and distortion of the leaves and resulting honeydew from feeding by the nymph stage. The Center for Biological Control at the University of California at Berkeley began looking into the possibility of using biological control of this pest and by 1991 were focusing on a tiny eulophid wasp in the genus Tamarixia that had been brought back from New South Wales, where Syzygium paniculatum naturally occurs. This parasitic wasp was initially released in the Eugenia hedges at Disneyland in July 1992 and subsequent releases were made throughout California in 1993. Though there are still problem areas, such as in cool coastal cities such as San Francisco, or weather conditions such as cooler spring temperatures that effect control, for the most part this parasite has reduced the psyllid populations such that attractive Eugenia hedges can be maintained in the landscape without the use of pesticides. Nurseries must still maintain a program that keeps plants nearly pest free but once planted in the landscape it is best to not spray this plant as the balance of pest and parasite should be established. Occasionally there will be peaks in pest population with some lag in control but this is to be expected and applying a pesticide at these times will likely upset the balance and result in the need for repeated pesticide treatment that would otherwise be unnecessary. Shearing of hedges however can be an effective way of managing this pest, especially if the leaf trimmings with parasitized psyllid nymphs are left as mulch below the plants to allow the beneficial parasite to remain. It has been suggested that a three week interval of shearing and mulching in spring can maintain a pest free looking hedge. Like most nurseries we long listed this plant as Syzygium paniculatum but botanists now are confident that the plant long grown in California is actually Syzygium australe. In Dr. Robert Muller and Dr. Robert Haller's Trees of Santa Barbara (Santa Barbara Botanic Garden, 2005) their description of Syzygium australe notes "This species has been noted as S. paniculatum in previous versions; however, the merged wings forming a pocket, hump, or spur above each node clearly identify it as S. australe." Cal Poly San Luis Obispo botanist Dr. Matt Ritter further notes that "This species is often erroneously sold under the name Syzygium paniculatum, which is a rare species, also from eastern Australia and only occasionally found in California." Though easily maintained in the garden by allowing the beneficial wasp to control the psyllid, nursery regulations require that nurseries maintain entirely pest free plants, which is impossible to do by relying on the beneficial wasp alone and requiring regular pesticide treatments. For this reason in 2009 we decided to no longer grow it but still recommend it as a good landscape plant.
This information about Syzygium australe displayed is based on research conducted in our horticultural library and from reliable online resources. We also will relate observations made about it as it grows in our nursery gardens and other gardens we have visited, as well how the crops have performed in containers in our nursery field. We will also incorporate comments that we receive from others and we welcome hearing from anyone with additional information, particularly if they can share any cultural information that would aid others in growing it.
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