We see the leaves of what appears to be Wild Violet (not a vegetable, but a native wildflower), which can be quite common in home lawns and gardens. Their leaves feed Fritillary butterfly caterpillars, but in this setting, it will compete with the onions for moisture and nutrients, so should be relocated (if you want to transplant them) or removed (discarded). Since the onion (we only see one onion plant) may struggle to thrive in a container, you could also move it to a location in the ground, if available. Our Growing Onions in a Home Garden page has more cultivation information. The other plants growing as weeds in the pot are harder to identify (one in the front, one in the back), but one or both of them look like dandelion, chicory, or a similar-looking plant. There's a weedy grass in the front there too, but we can't tell what species it is.

Miri