If it is possible, we would like to see a photo of the whole crape myrtle, one of the area of the suckers and one that shows where the whole thing goes into the ground.
This will allow us to give you the best information.
Photos can be attached directly to this reply by using the Choose File tabs below.


Christine

Christine, 

Thank you for your response and request. The tree is planted in a small piece of elevated ground, surrounded by stones. Including the stones it extends out about 2' from the trunk. The height of this piece of ground varies from about 4" on one side to 10" on the other.
We had tree trimmed a bit last summer but not much.

I am attaching 6 pictures:
9738: Full view of the tree. Note: nearby tree to back side extends above height of the crepe myrtle.
9739: If you look closely you can see at least 7 suckers coming up outside the wall by anywhere from 6" to 36". The height of some of these suckers has been reduced by the lawn mower going over them.
9741, 9742, and 9743 showing different sides of the tree/wall.
9743: Here a removed a few stones to cut off a bunch of tall suckers coming out of the wall.
9744: This is hole I dug trying to get to the base of the root of a sucker that is 6 & 1/2' away from the tree. The hole's depth is 3". Perhaps you can see two parts of the sucker still present.
I've seen suckers come up as far as 15 to 20 feet away from the tree. When I first see them, they are quite small and I have cut them off at ground level. 

Your system is telling me I can only upload 3 pics. I will try to send the other 3 pics separately.

Thank you for the photos. We've received three of them, but that may be sufficient.

Suckers are normal for certain species of trees and shrubs. They are growth originating directly from the roots, and while their photosynthesis does feed the roots just like typical canopy branches do, they are not by only source of nutrition for the roots below them and their removal is rarely a serious issue for the plant. Sprouts emerging directly from the trunk or branches tend to have different names (water sprouts or adventitious shoots), as sprouts referred to as suckers specifically emerge from roots (this includes the very base of the trunk at ground level).

You can remove suckers by trimming them off at the soil line, or by clipping them off below the soil surface if you are able to dig down to that connection point. Do not cut the roots themselves if avoidable; just cut off the vertical shoot that develops into the stem with foliage. If in doubt, only cut off what you see above-ground. Sometimes, suckering is triggered by chronic or acute plant stress, but in some cases it's perfectly normal plant growth. Crapemyrtles do naturally sucker, though how vigorously they do this may depend on both the cultivar grown and the conditions in which the plant is growing. If the surrounding lawn is fertilized one or more times per year, perhaps the nutrient boost (which crapemyrtles don't need) is stimulating surplus growth. At this size, its roots will easily reach well beyond its drip line.

Professional arborists could apply a chemical formulated for discouraging sucker formation in trees, but this is usually not necessary and we do not know if these products have any potential negative side-effects on other organisms. It also might be an expensive endeavor that won't work reliably if several environmental triggers are causing the tree to respond by suckering. (Technically, these plant growth-regulating chemicals are classified as a pesticide, even if they are not intended to kill a plant or pest in this case. Some might only be legal to apply by licensed pesticide applicators.) A systemic herbicide that the plant absorbs cannot be used because it risks damaging the rest of the tree, and a contact herbicide (like organic products) will only serve the same function as trimming - they will kill or weaken individual sucker top growth but not prevent recurrence in the future.

Since the tree shades the lawn at its base, and shade can eventually cause turf to decline due to lack of sufficient light, it might be worth expanding the mulched zone around the trunk base to encompass a wider area. Unless it is used for aesthetics, maintaining the stone edging around the tree is not necessary. Although suckers might still re-appear in the mulched area, at least they would not interfere as much with the lawn growth or mowing, and might be easier to spot and remove while small.

We're not certain why the plant is suckering so much now compared to when it was younger, when we presume this wasn't an issue. Perhaps the trimming last year triggered this reaction. While crapemyrtle is quite tolerant of trimming, it can be stressful for them depending on how much growth was removed.

Miri