Before anyone can suggest what to plant, we need to know where you live. City & state is certainly helpful.

Sorry if my post was unclear, I know what I want to plant but need to get rid of the weeds.

I am in Colorado, south of Denver. Zone 4B.

What's a 'spearmint tree'?

Spearmiont tree, "Juniperus chinensis", common name Chinese Juniper. Keep in mind that "weeds" are an ever occuring problem for every gardener, there is nothing that will eliminate "weeds" since they seed so prolifically. Spraying plant poisons will kill off the "weeds" growing today but more will germinate and grow tomorrow so it is a never ending battle if all you do is spray those plant poisons around.
"Weeds", like any other plant, have soil preferences and will grow best in the soil conditions they prefer, usually not the soil conditions a good healthy lawn prefers. So take a good look at the soil you have and correct that and you may well reduce your "weed" problem.

You can apply a glyphosate containing product as long as you have not had a killing frost yet (around 28-29 degrees or lower) and still safely plant bushes later this fall or in the spring. If the weeds are annuals, spraying them now really doesn't accomplish much as they are about to die anyway. If they are perennials, this is a good time to go after them. If you've had a killing frost, the perennial weeds may still look green but glyphosate just doesn't seem to soak in and do much.

I would get a pitchfork and start digging the weeds up, then mulch heavily as quickly as possible to prevent seeds from sprouting.