"How do you kill bittersweet?" is an answerable question, but not one that can be answered without making certain qualifications. You will be able to remove it only gradually, over the course of time. You can kill bittersweet enough to make control manageable relatively quickly (although only with hard work, and only if you are persistent), but complete removal of the Oriental type is difficult. For killing this tough invasive plant, I recommend a multi-pronged approach, as described below.
Reader, Jonathan writes:
Thanks for your highly informative piece about how to kill bittersweet. My question goes a bit beyond the scenarios your piece contemplated.
I have terraced front and back yards that are surrounded by wooded areas and shrub plantings. Through my own neglect, I allowed Oriental bittersweet vines to become very established in these surrounding areas. Last year, I tackled my kill-bittersweet project by pulling the vines down from the trees and bushes they were choking.
This year, to my chagrin (OK, panic), the Oriental bittersweet has invaded the lawn terraces, especially at the back, and marched with breathtaking rapidity all the way down five levels to the house.
It seems clear to me that spraying won't kill bittersweet in my case because, among other things, the "home base" of this stuff is up in the "jungle" areas above the lawn, and I was physically unable to uproot the rhizomes even in the shrub and tree areas where I cleared the vines.
I also don't see that ripping the rhizomes out of the lawn will have much effect (other that putting me in a back brace) since they will just regenerate.
I'm just about resigned to bringing in heavy equipment and ripping out the entire landscape, since I'm looking to sell the house in two or three years, but can't really afford this solution financially.
Short of using Agent Orange, how do you kill bittersweet in a case like this? It wouldn't make much sense to try to pull it out by the rhizomes, would it?
How to Kill Bittersweet
Jonathan's question is a common one. The answer, essentially, is as follows:
"I feel your pain. I'm trying to kill bittersweet, myself; frankly, there's no end to the battle in sight on my property, either. Although there is hope: I waged a similar battle with Japanese knotweed and can largely claim victory at this point over that dreaded monster.
"As in my battle with Japanese knotweed, there's no magic bullet to kill bittersweet. Short of starting all over (which, as you state, you cannot afford), the only sensible approach is a multi-pronged offense against the Oriental bittersweet. And you must be willing to carry it out faithfully year after year.
"Multi-pronged approach to kill bittersweet:
- Cut off vines scaling trees, at their base: without their roots, they can't thrive in the 'jungle canopy.'
- As soon as you make those cuts, swab some Roundup onto the stumps sticking out of the ground (you want it to travel down to the root system)
- Hand-pull the new vines whenever you see them pushing up out of the ground somewhere.
- When there are too many to hand-pull, use a spray (although, remember, a non-selective herbicide such as Roundup will kill everything, including any grass and shrubs it falls on).
"Even though you're not removing the rhizomes from the soil, their strength will eventually be sapped if the accompanying foliage is severed from them since photosynthesis won't be able to take place. But for a long while, you may have to be content with just lessening the problem, rather than killing bittersweet, outright.
"As far as rhizome removal is concerned, I, myself remove the rhizomes from the soil whenever I happen to come across them (when I'm transplanting trees, let's say, or otherwise tinkering around in the garden). But I don't go out of my way to perform a "rhizome hunt." Trying to remove all the rhizomes from the soil strikes me as just too problematic an undertaking.
As you suggest, leaving behind the slightest trace of rhizome will result in regeneration.
"Keep at it, and don't get discouraged: A realistic goal is to make control more manageable over time, not to kill bittersweet anytime soon."