I've tried each of the cover plants you mentioned.

Corn can make a good dense screen, but wants a heck of a lot more nitrogen than weed so they really shouldn't be grown in close proximity in earth. I plant small patches of corn strategically to block potential lines of sight, but weed growing close by will be in a pot.

Sunflowers sound like the perfect crop, but they are far from it. They grow straight up on a single stem and once flowering, lose all the leaves up their stems and any potential they had to disguise your plants. Also being so tall, they attract attention to the area you are trying to hide.

Tomatoes, well they can and do pass on fungal and viral problems to cannabis and if they were planted early enough to cover your vegging growth, they would have long finished before a sativa is through flowering.

Cannabis in flower is very distinctive and I have found it difficult to hide within a single species crop. I now plant a large mixture of different vegetables and keep my plants tied low. They seem to camouflage better amongst a variety of different leaf shapes.

I haven't tried it, but I think bamboo might have some potential. That is, of course, if you can control the spread of the bamboo.

Happy Gardening :hippy: