Two often overlooked sources of oriental bittersweet infestation are mulch and nursery stock. This subject came up at a recent discussion among several Bittersweet Battlers and it was remarkable how common the problem is.
The problem occurs when the mulch being applied to a garden or around trees and shrubs is of low quality and contains "whatever went into the chipper." This can include bittersweet vines with seeds intact. The seeds can survive the chipping process and will appear in the spring as seedlings.
Many property owners allow their landscape or tree service to chip cut wood on site and blow it into a "mulch pile" which is then used around the yard. Any bittersweet berries that were in the debris will cause problems.
Even when bittersweet is disposed of in the brush pile at the landfill, if there are berries on the vines they can end up in the "free mulch" pile after brush is run through the chipper. When that happens the free mulch is no bargain.
Several Bittersweet Battlers have also noted persistent bittersweet infestations that originated in mulched areas on the grounds of commercial properties. This can be a problem when property managers and/or landscape service providers don't spot the infestation or don't know how to identify oriental bittersweet.
You may never quite be sure if your oriental bittersweet came from a passing bird or from infested mulch because mulch is typically spread under trees and shrubs frequented by birds.
The lessons are: Know where your mulch came from, and avoid mulch that was chipped from land clearing debris. Be especially careful of material that was chipped after mid-July. If the chips are from your own property be sure no berry-laden bittersweet goes into the chipper. Use high quality mulch. Poor quality mulch attracts insects and promotes disease. Putting down too much mulch ("mulch volcanos") will ultimately damage trees.
Some nursery growing areas are infested with oriental bittersweet. As a result when plants are dug and balled there can be bittersweet seeds, plants or root segments that can sprout when you plant the tree or shub on your property. As you plant any new tree or shub look for the telltale orange roots of oriental bittersweet and gently pull them loose if you can, without damaging the tree or shrub's root system. Check the new plant periodically for any oriental bittersweet sprouts.