Elaeagnus pungens

Elaeagnus pungens a/k/a (thorney olive or silverthorn)

By Deborah Lawson

My first experience with silverthorn was when Mike and Cadence Bozeman lived at the end of the common land in Sunrise Community.  They hired me to make major changes to their landscape and in doing some much needed cleanout, we discovered silverthorn that had been planted by a previous landscaper to camouflage the above-ground propane tank. Sadly, the silverthorn which grows at a rapid pace, had taken hold of a large live oak tree at the corner of the property and climbed all the way into the tree canopy literally shading out the tree and causing its decline.  We had to hire a tree service with a crane to remove the silverthorn itself, but especially the thorny vine that had taken over the tree canopy.

Like many invasive exotics, silverthorn is native to Asia and Japan. It is loved for its fast growth and salt tolerance. I have friends who have planted at their beach house because of these characteristics, but of course there aren’t large trees on the sandy beach for it to compromise.

According to Wikipedia it is a dense, branching shrub which can reach over 23 feet tall by 13 feet wide. It sprouts prolifically from its stem, spreading out and twining into adjacent vegetation. In my experience described above, with something to climb on, it was well over 45 feet. Parts of the stem are covered in thorns which can be up to 3 inches long. The undersides of the leaves are silvery white with brown flecks (hence its common name). Tubular flowers are borne in clusters of up to three. The flowers are yellowish or white and are sweet-scented. The fruit is a drupe up to .59 in long which contains one reddish seed with silver scales. Blooming occurs in the autumn and fruit develops during the spring. The plant grows quickly, with shoots growing over one meter per season. The growth has been described as "aggressive", with shoots extending many meters into neighboring treetops. And of course, the main reason they are invasive…the seeds are dispersed by birds and other animals which easily spread and germinated in our subtropical environment.

This plant was originally introduced to the Southeastern United States in the 1800’s as a hedge plant, often planted on roadsides.  Manual eradication can be difficult often requiring heavy equipment to remove the aggressive and thorny root system.  The plant is on Florida’s Invasive Plant list and it is recommended not to plant it.