How to Kill Mexican Hydrangeas
Neither from Mexico nor a hydrangea, the Mexican hydrangea (Clerodendrum bungei) is native to southern Asia and displays leaves and flower clusters that mimic those of a hydrangea. Also called cashmere bouquet, it is grown around the world in subtropical gardens. Although the fragrant flowers are beautiful and attract butterflies, this shrubby plant grows quickly into weedy thickets, spreading by roots and any seeded blue fruits that germinate. Killing this plant is relatively easy, but requires diligence and thoroughness. Does this Spark an idea?
Things You'll Need
- Glyphosate-based herbicide
- Potato fork
- Garden shovel
- Hand or bypass pruners
Instructions
-
-
1
Spray an herbicide containing the active ingredient glyphosate on the leaves of Mexican hydrangea. Follow the label directions for safety precautions, appropriate dosage rates and other advisories. Coat only the leaves of the Mexican hydrangea plants; avoid getting nearby desirable garden plants wet with the spray. The leaves absorb the chemical and transport it throughout the plant, including the roots, weakening it. A couple of days after herbicide application, the leaves wither and drop.
-
2
Dig up the roots of the Mexican hydrangea with a potato fork or garden shovel. Start at the outermost plant stem in the thicket, inserting the fork or shovel at a shallow angle to lift up the roots. Once exposed, you can trace the roots to other plant stems in the center of the thicket.
-
-
3
Pull up on the base of the plant stem while simultaneously lifting the root and soil with the shovel. Rock the shovel as needed to expose more root to pull up. Expect the roots to snap off, leaving remnants in the soil. Continue to dig up the trailing bits of root as you work inward toward the center of the plant mass.
-
4
Remove as many stems and roots as possible in the garden by pulling and digging. Monitor the garden over the next two to six weeks, looking for new sprouts of Mexican hydrangea. These sprouts reveal roots that remain alive.
-
5
Spray the sprouts of Mexican hydrangea with glyphosate-based herbicide or prune the stems back to the ground with hand pruners. While digging up the roots of existing plants is a faster way to kill them, repeated spraying and/or pruning prevents the plants from photosynthesizing light. The plants become weaker, as there are few food reserves left in the deteriorating roots, and eventually die.
-
1
Tips & Warnings
Digging up Mexican hydrangea's roots is much easier when the soil is evenly moist, such as in late winter to late spring. Irrigate the garden a day in advance of digging to loosen the soil if it's during the drier months of summer or fall.
Herbicides are more readily absorbed by actively growing leaves, such as in spring and early summer when leaves are tender and enlarging. Summer and fall spraying usually is less effective.
You may avoid using any herbicide to kill Mexican hydrangea by digging up the roots. This effort requires several months of followup monitoring to remove all remaining root segments and sprouting plants.
Winter cold and seasonal drought won't kill the plants. Mexican hydrangea simply goes dormant, dropping its leaves, but survives in its roots and sprouts again once better growing conditions return.
Do not discard dug-up Mexican hydrangea in your compost pile or in a debris mound in the garden. Any roots that remain moist in the pile will continue to grow and create new plants. Likewise, any plants that have bloomed and are producing seeds should not be composted or placed where seeds may later drop and germinate. Ideally, place these weedy plants in a plastic or cardboard box to dry out and go to the landfill.
