Plum grove guidance

I am new to a couple acres with various degrees of cultivation and neglect. It's a lot. Recently I decided to start in on a "grove" of tiny Plum trees. There is obviously an old mother tree and a bunch of slim, crowded  trees around her. I started cutting them back for a walkway and trying to salvage the fruit. The area is kind of a disaster. It was someone's debris pile and the extra trees started growing about 5 years ago with the previous inhabitants (I have big feelings about the people who lived here then and those feelings usually dont involve a smile).

From what I understand, these are Italian plums and they *should* be sweet but unless they are nearly rotten, they are essentially bitter. I think these grow from seeds so wouldn't be weird suckers or root stock getting out of hand. They are so dense that I can't access the mother tree yet.

My questions:  Am I just THAT unlucky in my selection of fruits to sample or is there a reason they are bitter?

What is the typical lifespan of a Plum? She's about a foot across but there's a good possibility she's being choked by a hose

If the young trees are from seeds, will the fruits improve with age?  (As in worth keeping a couple)
How much can I prune (haha) a plum's height? They are all tall and skinny so near inaccessible fruit.

Photos of the area and the canopy as best I can get since there's a steep bank directly behind me. Also, the fruit I gathered from the ground + the ones trimmed today.

ETA: to the left is an apple that fell over and is doing it's best to try to be a tree still. It only bore fruit on one side, but that's another thread for later!

If they are soft enough that you can press the flesh and dent them, they should be pretty sweet!  I don't some across many bitter plums when ripe and soft.  You can look for little holes and leaking sap that are signs of worms.  But a very ripe plum will be soft and drip juice when you bite it.

As for managing the thicket, try to cut off growth that is sideways and below 6 ft or so.  Plums will overgrow vertically and break branches if not cared for.  If you dig small seedlings in the winter when dormant, you will quickly find out if they are true seedling or root suckers.  Probably most of them are root suckers..

Eric Thompson wrote:If they are soft enough that you can press the flesh and dent them, they should be pretty sweet!  I don't some across many bitter plums when ripe and soft.  You can look for little holes and leaking sap that are signs of worms.  But a very ripe plum will be soft and drip juice when you bite it.

As for managing the thicket, try to cut off growth that is sideways and below 6 ft or so.  Plums will overgrow vertically and break branches if not cared for.  If you dig small seedlings in the winter when dormant, you will quickly find out if they are true seedling or root suckers.  Probably most of them are root suckers..

Thank you for the reply!

They're soft and bitter :/  they seem like they should be ripe.

Should the height be brought down? There doesn't seem like a lot below 6 feet at all.
Given the age of these, 5+ years, would digging be effective?

Look into grafting some other varieties on to them. Some research will show what varieties of peach, nectarine, apricot and cherry.  

Well, looks like I'm going to lose the big one wether I like it or not 😭