Prized for their silvery foliage and dense growth habit, eleagnus shrubs (Eleagnus spp.) work equally well as hedges and low-maintenance specimen shrubs. They recover quickly after planting, adapting readily to most conditions and producing masses of fragrant blossoms in summer. However, for all their good traits, eleagnus shrubs are not without drawbacks because they may self-seed and become invasive in warmer climates.
The hardiness and cold tolerance of eleagnus shrubs vary between species and cultivars. Thorny eleagnus (Eleagnus pungens) and variegated eleagnus (Eleagnus pungens "Maculata") grow best in U.S. Department of Agriculture plant hardiness zones 7 to 9, while Russian olive (Eleagnus angustifolia), autumn olive (Eleagnus umbellata) and silverbush eleagnus (Eleagnus "Quicksilver") are more cold tolerant and grow best in USDA plant hardiness zones 4 to 8, 3 to 8 and 2 to 8, respectively.
Site Selection and Preparation
Most eleagnus shrubs perform best in full sun, although evergreen species benefit from light afternoon shade in warmer climates. They are not picky about their soil, but it must be fast draining with moderate fertility. Avoid areas where water pools after rain, as well as heavily shaded sites. Weed and till the planting site to improve the soil texture and drainage, removing any stones or other bits of debris from the site. Do not amend the soil before planting because it discourages the shrub's roots from extending beyond the amended area and can cause drainage problems.
Timing and Spacing
Eleagnus shrubs should be planted in autumn where hard frost and snow are rare, and in spring several weeks after the last frost in colder climates. Dig a planting hole that is two to three times wider than the shrub's rootball and of the same depth. If drainage is an issue, dig a hole that is 2 inches shallower than the rootball. Spacing depends on the shrub's mature spread, which varies between eleagnus species. Space thorny eleagnus 12 feet apart, and autumn olive 10 to 15 feet apart. If growing eleagnus as a hedge, dig a planting trench and space them 4 to 6 feet apart.
Eleagnus shrubs may develop compacted or girdled roots during their time in the nursery, so they may need a little extra attention at planting time. Remove the shrub from its pot or burlap and inspect the roots. If they are coiled around the outside of the rootball, make a 1- to 2-inch-deep slice from top to bottom in three or four different places around the exterior. Settle the rootball in the center of the hole and have a helper hold it upright to keep the trunk straight. Backfill around the rootball with unamended soil until it is completely covered. Water to a 12-inch depth after planting to settle the soil and hydrate the roots.
Watering and Aftercare
Although highly drought tolerant once established, eleagnus shrubs need plenty of water during their first season to promote a deep, productive root system. After planting, build a 3-inch-tall soil ring around the outer edge of the shrub's rootball to direct water toward the roots. Fill the watering ring with 2 to 3 inches of mulch to conserve soil moisture. Provide roughly 1 inch of water weekly during the first summer, running water until the soil is wet in the top 12 inches. Cool weather decreases the need for water, so check the soil moisture and water only if it feels dry 2 to 3 inches below the surface.
A Word of Warning
The hardy, adaptable nature of eleagnus shrubs makes them a low-maintenance addition to any landscape. However, it also makes them prone to invasiveness. The state of Florida classifies thorny eleagnus as an exotic plant pest due to its ability to escape cultivation and colonize wild areas, where it displaces native plants. Planting sterile cultivars such as silverbush eleagnus (Eleagnus "Quicksilver") will help limit their spread, but it is still best not to plant eleagnus shrubs in areas where they are known to be problematic.