how do i get my puppy to stop trying to eat twigs, rocks, etc. outside?

Hi everyone!

My boyfriend and I recently adopted a 3 month old retriever mix (we suspect he’s a lab/german shepherd mix) and he’s been doing great with training and getting adjusted, aside from this one thing that I’m looking for help on.

Every time we take our puppy outside, he constantly is trying to chew on grass, twigs, rocks, etc. We’re very vigilant and instantly take out whatever’s in his mouth, but that doesn’t stop him. He will go right back to looking for the next thing to put in his mouth.

I’ve had to put my finger almost down his throat to keep him from swallowing anything, lift his tongue, you name it, which I know can’t feel good for him, but even that doesn’t stop him from wanting to eat everything outside.

Is there any advice on ways I can try to redirect him? I tell him “no” which works for everything except this, and apparently he doesn’t care about us having to be all up in his mouth, so I’m at a loss. I also don’t want to confuse him and have him think he can’t sniff around outside because, of course, we’re potty training and he needs to be able to use the bathroom outside and explore. And, of course, we don’t want him ingesting something and getting sick.

Any advice is greatly appreciated, thank you 🙂