Yes, I would think that most large trees are damaging by roots and maybe by shading.

Sounds like a general shortage of nutrients.
A soil test would give a definite answer, failing that add some Epsom salts for magnesium, and possibly some Urea for nitrogen.
I don't think there is 'bad' soil, just stuff that needs amending.

The balance of nutrients may be out of whack. Get a soil test and see what it says. They usually make recommendations. If you grow naturally/organically, be sure to write ORGANIC on the paperwork.

It just isn't possible to keep taking from the soil and continue to get good crops. Vegetable growing is hard on the soil because you generally remove a lot more than you return.

But nearby tree roots may also be taking the nutrients and moisture away from the other plants.

Sue

There is an area, under a pine tree (actually two) where some Columbine and Black Eyed Susans decided to self seed and grow really well producing blossoms every year with little attention from me so it is not very liklely that pine is at fault.
How much organic matter is in that soil?
How well does that soil drain?
How well does that soil retain moisture?
What is the tilth of that soil?
What kind of life is in that soil?
What is that soils pH?
What are the nutrient levels of that soil?

Back when I did grow a garden we planted some corn in several rows parallel and south of an east-west row of pines. Each row further away from the pines was around 6 inches taller than the ones closer to the trees. Whether it was nutrients or moisture I don't know but the trees had an enormous effect on the corn.

Lloyd

My first thought is to agree with the tree theory. (In spite of the fact that there was this one guy in this one place with these two plants that did well under this one kind of pine tree.)

I'm assuming that the whole garden gets amended the same, fertilized the same, watered the same and grows similar crops and/or they are rotated through spots in the garden. If that's the case, I would expect nutrients and general chemistry to be relatively uniform throughout and not likely responsible for plant performance that is not uniform. I could be guessing wrong about your cultural practices though. If you want to pursue that possibility, I would recommend collecting two samples; one from the poorly performing area and a second from the area where plants perform well and compare.

Another thing that comes to mind as a possibility is nematodes. You can bring those in on plants pretty easily from the nursery or big box store and they'll hang around year after year. Tomatoes are notorious for it. Keep in mind, some people think that if you don't see nodules on the roots, you don't have nematodes. However, root knot nematode is only one of the damaging plant parasitic species. There are root knot, sting, cyst, etc... You won't see those others with the naked eye. If you suspect nematodes, some labs can do testing to confirm whether or not they're present in your soil and/or roots. On a possibly related side note, nematodes love a well drained sandy soil.

Of course, soil borne plant pathogens, an area of poor drainage, uneven watering, soil compaction, etc. are among the many other possibilities.

I have a cottonwood and a silver maple that are getting big enough that I'm seeing fine netlike roots all through the soil at one end of the garden whenever I dig it up. Plants struggle in that area. I figure it's the trees stealing the nutrients and water.