1 - Roots stop growing fairly quickly after a tree is cut, but buds on the stump or roots may grow and require effort by the gardener to remove the shoots for some time.

Q.

Do tree roots grow after the tree is cut? I am specifically asking about the jacaranda tree in southern California? Does it easily develop sprouts if stump remains without removal?

- R. Chan

A.

I have never lived where the Jacaranda trees grow, so I am not familiar with their characteristics regarding basal and root sprouts. I searched the internet without much success for this information, so I will base my answer on general tree root characteristics that are relevant for many landscape trees in most locations.

Once the leaves are removed by cutting the tree, new root growth will depend on stored foods in the larger roots and tree stump. This will greatly reduce root growth. The stump may have dormant buds that may begin growing to produce new shoots and leaves. That process will greatly deplete the stored food reserves in the trunk, even further reducing root growth. Removal of sprouts soon after they form will prevent new leaves from photosynthesizing and replacing food reserves in the trunk and roots. The buds in the shoots also produce hormones that translocate to the roots stimulating root growth, so removal of sprouts further reduces root growth.

Ultimately, in the absence of leaves producing food for root growth and hormones from the shoot buds stimulating root growth, the roots will begin to die and decompose. This may lead to collapsing soil over the tunnels left by the decomposing roots. You may see mushrooms growing in the landscape over the decomposing roots as the fungus that produce the mushrooms feed on the decomposing roots. This is good for more quickly reducing the chance of sprouting.

So, in summary, once the top of the tree is removed, root growth quickly stops and the roots decompose. Sprouts may form from latent buds on the stump, but if the sprouts are consistently removed, or if the stump is ground away, this should not be a problem. I do not know if Jacaranda trees can produce adventitious buds on their underground roots, but many trees are able to produce sprouts from such buds. Once again removal of the sprouts should fairly quickly result in depletion of stored food to support new growth. The length of time that sprouts can be formed from the roots depends on the size of the roots, but root sprout production should cease within one to two years if you consistently remove the sprouts.

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.

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