Cider gum (Eucalyptus gunnii) is native to southeastern Australia's Victoria and Tasmania states. It is among the most cold-tolerant of eucalypts, surviving winter temperatures as low as 5 to 10 degrees Fahrenheit. Gardeners in U.S. Department of Agriculture Hardiness Zones 8 through 10 cultivate it for its attractive silvery-blue foliage as well for providing shade, windbreak or visual screening. It bears tiny creamy-white flowers in early summer, and deer stay away from its scented foliage.
Cider gum is an erect but spreading-form evergreen tree. It matures anywhere from 30 to 80 feet tall with a canopy width between 20 and 50 feet, according to "A-Z Encyclopedia of Garden Plants." It is densely covered with twigs lined with many leaves. It attains a bushier look than most other eucalyptus trees grown in garden settings.
Cider gum is a fast-growing eucalyptus tree, increasing its size or individual branches between 3 and 5 feet per year. When a sapling, annual growth is as much as 8 feet. While cider gum is drought tolerant, it needs ample moisture to keep the soil evenly moist in the heat of spring and summer increasing growth rates. Monrovia Nursery recommends a light application of a gentle, balanced formula of fertilizer in spring (such as 5-5-5 with iron) for best new growth.
Two distinctive types of growth occur on the cider gum tree. Newly germinated plants, saplings and branches that sprout from trunks or wounds produce "juvenile" foliage. Juvenile leaf blades are rounded and mid-green with a powdery film atop that creates a striking silvery blue cast. Older trees and branches produce "adult" foliage that is dark gray-green in color, tapering and lance-shaped.
For best performance of cider gum, plant it where it receives at least eight to 10 hours of direct sunlight daily. A well-drained soil that is moist in the growing season promotes lushest growth, but once established this species tolerates a fair amount of drought without harm. Irrigation is needed only in the hottest lowland desert gardens. Over-watering can lead to iron nutrient deficiencies manifested by yellowing leaves, according to "Sunset Western Garden Book."
Prune out dead branches on the cider gum any time of year, but if severe winter cold occurs, refrain from pruning until mid-spring when definite regrowth is visible. According to "Sunset Western Garden Book," if your region is plagued by eucalyptus long-horned beetles, delay major pruning tasks until late fall or very late winter to deter beetle infestations. New side branches develop below the place where a stem or branch is pruned.