If you can't recognize most of the plants in the produce section, you really oughta be eating more fruits and vegetables. I don't really like veggies either and I still know more than 10 plants just in the category of food you can buy with a corporate logo on it.
You R E A L L Y want to get your carrots/parsnips right when it comes to ID, though. Water hemlock is fatal if ingested, and several parsnips will give you gnarly blisters if you come into contact with their sap
And the carrot plant looks near identical to Giant Hogsweed because they're both in the same family. One has a delicious carrot underneath and will do you no harm, you can even eat the green tops. The other will cause you severe burns even just by brushing against it. The plant itself doesn't even burn you, it destroys the skin in such a way that sunshine is what burns you.
hogweed is hogwild. my wife has these strange white scars all over her legs, arms, and chest because she was weed whacking in shorts and a spaghetti top and hogweed juice sprayed on her. she has somewhat darker skin so the scars stand out. she does not weed whack in anything but full coverage now. the scars are slowly fading but it's been about 5 months and they're still very prominent.
Giant hogweed really is quite large, often more than head-height - you're more likely to confuse carrot with cow parsley or hemlock or maybe yarrow, I'd have thought.
onion flowers are my favorite type of flower. when they're in full bloom they get so pretty. i have a patch of bunching onions that i barely even eat, just keep them for the flowers each year. the patch is growing because each flower produces dozens of seeds
You can also cut the flowers off after they open, and submerge them in white vinegar for 2-3 weeks, then strain. I do this with chive flowers (packed into the jar, but not so much there’s no room for liquid) and it makes a bright pink garlic chive vinegar that is really lovely. Onion would do the same, but probs look and taste a bit different.