How do I remove one of two different plants growing in the same spot?

Question

There's a shrub planted in the corner of my property, that the previous owner put there to help mask the utility pole behind it. I kind of like this idea, but there is another plant growing in the same spot. I feel like the shrub would be healthier, fuller, and overall better-looking, if I removed it.

The problem is I i'm not sure how to effectively remove one plant without harming the other. Is this even possible? If you look at the closeup below, you can see the trunks - I want to keep the larger plant with the chunky-looking bark, and get rid of the smaller plant with smooth bark.

I've had some success killing hackberry saplings in my back yard by cutting them near grade with lopping shears and painting the top with glyphosate, but I'm afraid that if I do that, it could enter the root system of the larger shrub. Is that an actual possibility, or will the glyphosate remain only in the target plant? If not, how should I go about this?

Answer 1

It's hard to tell from the picture, but I think that may be a tree of heaven that sprouted there. If that's the case if you just cut it to the ground it will come back over and over again but if you keep cutting it back it will eventually die. Like stormy suggested, that's what I would do. If you don't want the hassle, I think that painting the freshly cut stumps with glyphosphate would kill it, and I don't think it would affect the shrub. Keep in mind that is a small amount of chemical and it will enter the tree of heavens root system, spread out and would be pretty inert by the time the roots decompose. I certainly would not worry about it hurting the shrub.

Answer 2

I would just take a pruning saw and chop the newcomer to the ground. If it starts to regrow just chop the new growth down. It will die from starvation and you won't have to worry about surgery!

You need to create a plant less tree/shrub circle around your...lilac? Crepe Myrtle? Do at least a 3' radius circle.