Pick them all, seed them and make a shitton of plum jam

Wine.

I'd be making jelly or wine like there was no tomorrow. Plum wine in special is delicious.

There's a recipe here, if you want; it works for fruits in general, not just grapes. Note: most equipment can be improvised with some redneck engineering, for example my water lock is simply a piece of flexible tube forced into a U shape with an old hair rubber band, and filled with water.

You could also share the plums with neighbours. Bonus points if you manage to barter them for something else.

Jam, seriously. Plum jam is amazing.

If you want to use them up, this website has a bunch of suggestions.

If you just want to get rid of them, why not encourage the bold humans who've been plucking? Put up a sign saying "Free plums!", I bet it would be picked clean within a day or two.

Attract some parrots and you will rapidly have a garden full of drunk parrots lol

You probably have food banks in your area which would be delighted to get some!

search for tkemali sauce recipes. It's a Georgian plum sauce that is great with meats and vegetables. I've used it on pork, chicken, fried potatoes. In Georgia, it is about as common as ketchup is in the USA. There is red tkemali made from ripe plums and green made from unripened. Green is my favorite, but both are really good. I think the plums used in Georgia are a wild plum, but I made some last month with red plums I bought at Kroger. You might have to visit an international market to get some of the spices.

edit: recipe that i used, minus a couple spices i didn't find in time, but it still turned out good.

Plum jam

• plums
• sugar
• heat

That is all

If avoiding the ant-ageddon is your main goal, pick them and give them away. Free plums sign like others have said? Idk if I'd expect someone to pick them though, I'd pick them and bag them myself.

If it's like what do you DO with a million plums after they're picked, I'm plum out of ideas besides give them away. The jam and wine suggestions sounds interesting. Plum pudding mayhaps?

Tell all the neighbors they can have free plums if they pick their own on a certain day

For 1kg of plums:

Base shortcrust:

• 300 g flour
• 200 g cold butter
• 100 g sugar
• 1 egg
• 1 small pinch of salt

(Egg is debatable it's shortcrust, after all)

For the crumb shortcrust:

• 150 g flour
• 150 g cold butter
• 80 g sugar
• 1 small pinch of salt

Buy good butter with some actual taste from cows eating actual grass, not hyperindustrial stuff fed on nothing but soy it's worth it.

Mix both doughs individually, wrap them in cling film and chill for at least 30 minutes. A kitchen machine definitely helps with that one note there's no water (but in the butter), if you use a machine make sure to not overwork the dough. If in doubt, read up on shortcrust.

Halve and seed the plums, then roll out the base dough, laying the plums on top, cut side up. Quartering also makes sense if you prefer but don't puree them. Crumble the crumb dough over everything, bake at 180C for ~60m.

The fairy should come dancing by soon, right?

Make lots of plum wine. I shit you not, it's delicious.

And so is damson wine by the way.

You’ve already gotten advice on preserving, but what about sharing/donating the bounty?

Some cities have public portals where you can post the location of your fruit tree and indicate people can help themselves. There’s also this webpage. And failing that, you could reach out to a local foodbank - they may be able to have volunteers come collect the fruit?

Pálinka

Pic of the tree so we know what we're dealing with?

National center for home food preservation is a trusted resource for preserving food. All of their recipes are scientifically tested to ensure safety.

https://nchfp.uga.edu/

There's a bunch of plum stuff there, Google plum site:nchfp.uga.edu to get a list.

Make plum liquor

Throw a load of them into the garden of your most hated enemy and watch them fall to the ant apocalypse instead.

a few bold humans who I’ve caught plucking from the tree

Let them. You're about to have more plums than you know what to do with, and yes leaving them there will get gross and attract all kinds of critters; you should encourage people to pick your plums, or pick them yourself and give them out. People are suggesting making jam and pies and such but that's a lot of additional work compared to just dumping them on your neighbors.

For picking plums, i recommend using a broomstick or curtain rod to shake each branch, all the plums fall, you pick them up. This should be done a few times a year.

Plum liqueur (soak in vodka, with Cinnamon, ginger, simple syrup -- lots of recipes online). Delightful stuff, we went though last year's supply by February.

Mmm, make plum compote and gift a big jar to all your neighbours and jumpstart you career as the beloved neighbourhood grandma

Local food not bombs groups might be able to use them, or at least direct you at someone who can.

Be advised: the methods given here to make things like wine and jam are missing crucial steps in process. They are going to taste bad at best and at worst... a lot of food borne illnesses in the future of anyone who takes advice here at face value.

Canning and wine making are very specific processes.

Plum wine

I've plumbed the depths of my mind for a solution, but I got nothing 🙃

Wine. Throw them all into a container, add some water, close the container. Open the container every now then or it might explode, after the first day you probably only need to open it once a day. Do that for two weeks, the bottle it or, if you are feeling fancy, buy a cask and age it there I guess. I just did pomegranate wine as an experiment since I never fermented anything, it tasted alright. I did use bread yeast but I'm convinced I didn't actually needed that and the wild yeast was sufficient.

Eat/make what you can and compost the rest.