Rhododendrons are hardy bushes that produce colourful flowers in the spring. They are difficult to kill by simply digging them up because of their extensive root systems. Cutting the rhododendron back is also ineffective because it will produce regrowth the next season. To completely kill this bush, combine cutting back with an appropriate herbicide application. Once the stump is dead, it can be dug out if it won't disturb nearby plants.
Kill the rhododendron on a dry day, which will allow the herbicide to remain in place for optimal effectiveness.
Employ a hand saw to cut the rhododendron off at the trunk. Make the cut as close to the ground as possible. If the trunk can't be accessed because branches are in the way, cut the branches back first with pruning shears. Discard the removed portions of the bush in the trash.
Fill a bucket with a solution of 20 per cent glyphosate herbicide and 80 per cent water. Dip a paintbrush into the solution and immediately paint the wound on the stump with the herbicide. Do this as soon as the bush has been cut down.
Monitor the stump for regrowth. If the stump sprouts new growth, spray it with glyphosate herbicide according to the package directions.
Once the bush is dead, the stump can be dug up with a shovel if desired. Digging it out requires the removal of the dead root system to prevent regrowth, and this may disturb nearby plants.