I started seeing these weed around my property last year and did not know what they were so I started doing some research. After a little looking I found out it is called horsenettle (solanum carolinense).
Let me tell you a little about this weed. It's pretty nasty stuff, it will pop up in the yard, flower beds, veggie beds, everywhere.
The leaves look kind of like potato plant leaves when the first emerge and smell like potatoes when crushed. It has small berries that look like little yellow tomatoes.
Horsenettle is a very persistent noxious weed that needs to be removed from your garden as soon as it is detected. It is resistant to most herbicides to include broad-spectrum herbicide but can be used if done correctly. You can remove it by hand but be careful! When I say careful I mean careful! Horsenettle has sharp spines on its leaves and stems that I can tell you from experience are very painful.
When removing horse nettle by hand one more note of caution, the roots of the plant are deep and expansive. Do not leave any part of the root behind and do not chop them up with a tiller. Each and every one of the pieces left behind will produce a new plant.
After doing some research I have found that the best way to combat it is by timed intervals of mowing/cutting back and herbicide treatments. Start by mowing/cutting back in 30 day intervals starting just after flowering when the root system is weakened, forcing the plant to produce new top growth further depleting its root system. Then a treatment of herbicide in the fall after last mowing.
Once herbicide is applied do not mow for at least 2 weeks to give the treatment time to seep down through the plant to the roots.
If herbicides are not your thing horse nettle can be controlled but it will take longer and be more labor intensive. With diligent mowing/cutting back and digging out the roots eventually you can remove the plants from your property and garden.
Do not compost any part of the plant or root of this weed or you will re-infest your garden.
Well off I go to try to combat this nasty weed!