Leafy Greens and vegetables for an Australian Cattle Dog

Ok, Now I know this sounds odd but my 2 year old Australian Cattle Dog (Blue Heeler) loves to forage for vegetables in the garden. I'm ok with Him taking from the edges of my beds and Have trained him to stay out of the garden proper. He likes sweet and hot peppers, various greens and flowers.

Any recommendations on what not to plant, anything toxic?

It could just be a habit that he learnt from you.
Or he could be really sick and trying to self medicate

I,m mainly asking because he has gained weight since I cleared the garden. This has caused me to think that he just loves whats good for him like a smart omnivore. He loves Hot, he begs for habanero hot wing, hot sauce, and after he has reached his capsaicin limit he walks to the refrigerator and He gets a bowl of milk, and a piece of bread.
If it is a habit he got from me that's awesome! Shows that he is an extremely clever, social animal who loves me and views me as an elder.

My dogs have always loved veggies, fruits and leafy greens but I don't think they picked it up from me. I think it comes natural to dogs and most canines in the wild will forage on browse, berries, and roots along with the game that they kill.

I had to put a fence around my garden because the dogs~one in particular~were cleaning me out of tomatoes, potatoes, corn and melons. The worst garden raider would clean up apples out of the orchard all season. One day I counted his consumption and he had consumed 6 apples per minute. All apple season, this dog would poop red. The other dog would occasionally chew an apple now and again...this apple lover would eat them nonstop all day long. He'd have so much sugar in his system that he had the jitters!

House dogs just don't get the opportunity for this kind of foraging, so people don't notice it but dogs that live outside are constantly on the hunt for edibles even if they are well fed. One of my dogs is currently eating his way through a deer hide, hair and all. He will contest with the chickens over salad scraps and old fruit salads. He will eat bananas, peels and all. He'll sneak into the coop if the door is left open and eat the chicken feed and steal an egg or two...or a dozen. All the dogs will eat chicken poop and love any horse poop that they can get their teeth into. They love hoof trimmin's from the sheep and will consume a deer leg...hoof and all..in less than an hour. They will eat the whole head of a deer within a day of consistent gnawing.

Dogs are true scavengers and opportunistic eaters, just like coyotes, foxes and bears. Food is food, be it meat~ or veggies and fruit.

That's kind of what I was thinking.
Awesome that your dogs have such a healthy Diet, If we give either dog a bone its gone within a day for the ACD and the shi tzu lhasa takes about a week to finish one, he is older though and not as tenacious as he was in his younger days.
I HAVE NEVER OBSERVED HIM EATING POOP. I have however watched him pick up a pile of animal poop set it down 5 yards away, and proceed to smear it all over his neck. He ran up to me all happy with the "I do good?" face, then I gave him a bath. He has received the nickname Dingleberry.

It's good to know my dog isn't completely strange, but back to my question are there any plants that I should take care in planting, I just ordered some comfrey seeds, and from what I understand they are just a little toxic. should I plant it off in a corner, maybe behind the tiger lilies along the back fence. Also to get the maximum flea repelling qualities from tansies should I plant a border around the yard or just in the areas the dogs spend the most of their time, up by the house the gardens

All the things they say are toxic for dogs are bunk, IMO. Grapes? My dogs clean them off the vines as soon as they ripen. Garlic? Been using it as a natural dewormer and flea repellent for years on my dogs. Dogs usually won't eat anything that is growing out there that is toxic unless they are starving and have nothing else to eat. Animals pretty much know what they can and cannot eat...unless they live inside all their lives and aren't real tuned into their natural instincts. Usually toxic plants and bugs are very bitter and are not palatable.

I wouldn't worry too much. If they eat something that upsets their stomach, they puke it up or crap it out in short order~either way these processes take place outside and you'll probably never know they were affected. But, next time, they won't eat that thing that made them so sick.

I'm just being cautious. better to know and have nothing happen, than to not know and have problems.