There are two good reasons to kill a rose of Sharon plant (Hibiscus syriacus): because it's invasive and because it's toxic to pets. Because this plant spreads through suckers and seeds, killing it on the first try is a little tricky. It also has very strong roots that resist being pulled up by hand. With a consistent, vigilant effort and a few tricks of the trade, you can remove troublesome rose of Sharon for good.
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Remove Rose of Sharon Seed Pods
If the rose of Sharon plant has already gone to seed, it's imperative to carefully remove the dried seed pods before continuing to remove the plant. Jostling the branches when pruning or digging up the plant will knock the seeds loose, and they'll germinate easily wherever they land. In the spring, you'll have an even bigger problem on your hands.
Use pruning shears to carefully cut every single seed pod off the branches. Place them directly into a paper bag and dispose of it with your yard waste. Do not compost these seeds.
Cut Off Unwieldy Branches
With the seed pods out of the way, cut off any large branches that are in the way. You want easy access to the main stem, but it's difficult to get there with overgrown shrubbery blocking the way. Use loppers or pruning shears for smaller branches and carefully use a hand saw for any thicker stems.
Cut up everything into smaller pieces so they'll fit in a yard waste container. If it is legal in your area and safe to do so, you can also burn rose of Sharon wood to dispose of it.
Dig Up the Root Ball and Suckers
Pulling a plant up by the root is the best way to ensure it won't come back, but with rose of Sharon, this is easier said than done. The roots are very strong, so you'll need to gather some tools for extra "oomph." Various types of shovels and trowels are useful, as is a pick axe.
The best time to tackle this project is just after a rain. The ground will be moist, and it will be easier to dig into it. Push the shovel into the dirt at the base of the trunk and lever the dirt upward. Continue in this fashion all the way around the rose of Sharon plant until a circle has been dug around it. It's OK if the plant can't be completely removed just yet.
It should become clear where the main anchor roots are located. Use a smaller shovel or hand trowel to unearth these roots and then snip them free from the main stem with loppers until the root ball can be lifted up and out of the ground. Continue to follow the path of the roots, digging up and removing as much as possible. Do the same with any suckers you find throughout the area.
Preventing Rose of Sharon's Return
Rose of Sharon will continue to grow new stems from bits of root left behind. This is actually helpful, as the suckers are like little flags that help you locate the remaining roots. As long as you dig them up early in the season, they should not become too problematic. Eventually, you will succeed in completely eradicating this plant from your property. If digging up the roots isn't possible in your situation, you can paint an herbicide like Tordon on the freshly cut stems to kill the roots.