The forest provides, but not as well as a supermarket.
When you are walking in the forest, and you suddenly smell onions, don't panic.
There are several explanations and possibilities. You may have stepped on an onion, but that is unlikely. Other possibilities involve oniony plants growing underfoot, like these.
This is ramson (Allium ursinum), daslook in Dutch. I like to pronounce that as das Look, with a German accent, but that is just me. Really, nobody else does that. The plant looks like this:
Olympus Stylus 1s, 300mm, ISO200, f5.6, 1/250s
Another possibility is garlic root (Alliaria petiolata), look-zonder-look in Dutch, not in the Alliaceae family, but it does smell like onions, or garlic:
Olympus Stylus 1s, 300mm, ISO100, f5.6, 1/2000s
The leaves of both these plants can be eaten.
If you did, or ate onions, it could also be your own breath you're smelling. In that case, this little plant might help. Its clover-shaped leaves have a pleasant and refreshing acidic taste; they contain oxalic acid (so don't eat huge quantities, and avoid when you have kidney problems). The plant is called wood sorrel, (Oxalis sp.), klaverzuring in Dutch, and it looks like this:
Olympus Stylus 1s, 42mm, ISO100, f8, 1/500s
If stronger measures are required, you could chew the leaves of any of these three species of mint:
Water mint (Mentha aquatica), watermunt in Dutch:
Olympus Stylus 1s, 180mm, ISO100, f5, 1/500s
Field mint (Mentha arvensis), akkermunt in Dutch:
Olympus Stylus 1s, 42mm, ISO400, f5.6, 1/60s
Spearmint (Mentha spicata), aarmunt in Dutch:
Olympus Stylus 1s, 200mm, ISO200, f5.6, 1/60s
There's a hybrid of water mint and spearmint; it is called peppermint, which will also do nicely to get rid of your onion breath.
Now wasn't that hugely informative?