Hi gardeners, could you please help. A few years ago, we chopped down a dappled willow that had been grafted on another root. It repeatedly and vigorously sends out shoots. How do we deal with this problem? Should we use lime, and if so, how much, and how should we apply it (drill holes and fill them)? And will the lime affect the neighboring trees? With many thanks.
Dear Gardener,
Thank you for reaching out to Toronto Master Gardeners about your sprouting tree stump.
An extensive review of horticultural research did not provide support for the use of lime to control the growth of suckers (aka tree root sprouts, shoots). There are a number of online opinions/articles, not referenced to scientific sources, on eliminating root suckers. Many discuss chemical management such as herbicides (see note below). Various tree species such as maple, cottonwood, poplar, willow, etc. are prone to suckering. This response can occur due to injury or after removal of a live tree without preparation for its removal. Suckers can arise from trunks, stumps and roots as the tree attempts to regenerate itself, giving rise to the comment: “many tree stumps will not die – they just fade away“.
Hardier rootstock is used to support a less hardy grafted species as in the case of your dappled willow tree. The suckers, if not removed, will continue to nourish the roots. Consistent removal of the suckers is necessary to cause gradual nutrient deprivation of the roots. This will eventually deplete the energy reserves of the stump and its roots.
Residual lime in the soil raises the soil pH to a more alkaline level. The long term effects and duration of lime persistence in the soil, continues to be studied. Many, if not most, plants prefer varying degrees of acidity in order to make optimum use of nutrients within the soil. Altered pH can have uncertain and long term effects on the soil and surrounding vegetation. A soil which is too alkaline or acidic interferes with a plant’s effective use of minerals and other substances necessary to healthy growth.
Non-chemical methods of sucker removal are supported within the literature. The article, Trees and shrubs: removing suckers and seedlings, describes tearing rather than cutting the sucker away from the root to also remove nearby buds along with the sucker. This author has successfully used mechanical sucker removal over a three to four year period, gradually starving the stump and roots of a Lombardy poplar until it “faded” away. The neighbour, who also was consistently removing this poplar’s root sprouts, from their yard, hopefully commented: “Do you think we have seen the end of that tree?” The key to this method is persistence. Shoots allowed to grow will nourish the roots to which they are attached and the problem will persist.
For further information please see:
How To Kill A Tree Stump describes the use of slow release fertilizer to speed up decomposition
Note: When referring to articles published outside of Canada, please be aware that Canadian legislation prohibits use of many pesticides that may be legal to use elsewhere.
Wishing you every success in eliminating root sucker development. At some point, and with consistent persistence, you could succeed in outlasting the survival efforts of the roots.