The silverthorn's thorns are actually very pointy young stems. The one in the photo has just sprouted leaves and will soon elongate into a branch stem.
Silverthorn is a huge sprawling shrub that shoots scores of long branchless stems into the air during the growing season. If grown in the open and left unpruned this beautiful shrub will form a symmetrical mound of foliage that is up to 15 ft (4.6 m) high and 20 ft (6.1 m) in diameter, the ultimate size being dependent on variety and climate. The slender young stems are very pliable and very fast growing. These stems, or "canes" bend to form great arcs if unsupported. When grown adjacent to other plantings silverthorn canes insinuate themselves into the situation as they weave their way among the host's branches in an aggressive bid for sunlight.
These neatly pruned silverthorns in Tallahassee, Florida are helping to stablize this hillside - see how their roots are holding the soil while the open grassy area at the lower right shows signs of slippage.
Thorny elaeagnus, as it is also called, is a big and beautiful broad-leafed evergreen shrub. In the late fall and early winter it produces scores of flowers that are cream colored, bell shaped, about 0.25 in (0.6 cm) long and are held in small clusters where the leaf joins the stem. To call them drab and nondescript is an understatement. Yet they can grab your attention from hundreds of yards away with their seriously strong-scented but delightfully appealing fragrance.
These tiny flowers mature into dark small reddish brown fruits that have an unusual silvery textured surface. The fruits are a favorite treat for birds and are said to be edible for humans too. Floridata doesn't list silverthorn as edible because they're just not that good. They're tart, seedy and not worth the effort - leave them for the birds. If you're looking for edible, consider the silverthorn's cousin the gumi or cherry elaeagnus (Elaeagnus multiflora) which is a tasty treat.
These are the small, but powerfully fragrant, flowers of the variety 'Fruitlandii' - bees love'em.
Silverthorn doesn't have actual thorns and actually there aren't that many of these non-thorns on the plants anyway. This plant has the interesting trait of forming newly emergent branch stems into very pointed stiff 1 in (2.5 cm) spikes that feel very much like thorns if you jam one into your flesh. Eventually though small leaves sprout from the thorn and the pointy spike quickly grows into a soft young stem. The oval leaves themselves are very attractive and arranged alternately along the stems. Most silverthorn cultivars have leaves that are 2-4 in (5.1-10.2 cm) long and many have wavy edges. Leaves are green on top and covered with small brown scales, the undersides are lighter and ike the fruit and bark, the undersides are coated with silvery flecks. The popular cultivar 'Fruitlandii' has large leaves that are bluish green on top and grows to form great mounds. There are some smaller cultivars like 'Nana' and ones with flashy variegation like 'Maculata' (aka 'Auro-maculata) with bright yellow variegation and 'Marginata' with creamy-edged leaves.
Silverthorn is native to China and Japan.
Thorny elaeagnus is fast growing, easy to care for and tolerant of a wide variety of conditions. It is featured in both Peter Loewer's Tough Plants for Tough Places and Scott Ogden's Gardening Success with Difficult Soils. Light: Part to full sun. Moisture: Water when dry for best growth, but silverthorn is able to withstand drought even in light sandy soil. Constantly wet, soggy soil will kill. Hardiness: USDA Zones 7-9. Propagation: Propagated by softwood or hardwood cuttings and by seed.
This silverthorn 'Fruitlandii' wasn't pruned for two years and has engulfed a nearby dogword with its tentacle stems.
Silverthorn responds well to pruning and makes an excellent evergreen hedge and barrier. It is often planted along highways and is useful in controlling soil erosion. This adaptable plant is tolerant of salt spray and so is a good choice for coastal locations. In cooler climates, silverthorn is grown in containers and moved indoors when winter approaches.
The sweet fragrance of the flowers, reminiscent of gardenia, will delight in the autumn and winter garden (it reminds me of the perfume the old ladies wore to church when I was a kid). Silverthorn is very easy to grow and is bothered by few pests. Best of all it is a very fast grower - perfect for quickly creating a green background at the edge of your property. Place it on an expanse of lawn to create a great mound of wildlife habitat. The dense tangle of stems provide perfect sites for nests and the small red fruits will feed hungry songbirds during the winter. Be warned, however, silverthorn is not a good shrub for small areas as it will require constant pruning to keep in bounds - select one of the dwarf cultivars for tight spaces.
WARNING The Florida Exotic Pest Plant Council places this species in its Category II: "Invasive exotics that have increased in abundance or frequency but have not yet altered Florida plant communities to the extent shown by Category I species." Before planting, check locally to be sure that silverthorn is not a problem plant in your area.