Mystery Garden*

Ok, so this is the weird world I live in.

Back in February/March, I built a new raised flower bed in my front yard. LOTS of work. After putting in layers--newspaper, compost, manure, etc. (I'm lasagna gardening again this year!)--I planted a few things. Blueberries (two bushes), raspberries (one plant), some nasturtiums that I nurtured from seed (four or five, I think). I left it pretty open because I was going to go in later and plant some flowers. Pansies, daisies, whatever.

So after a while, I noticed a few seedlings popping up around the things I planted. I didn't pull them up immediately because 1) I didn't have time and 2) I was kind of curious. Who planted them? (I don't know, still.) What were they? Who many were there? And will the things that I planted survive amid all this other stuff?

I've deduced that most of them are either a squash or zucchini of some sort. And there are LOTS. There's some sort of melon in there--the vine at the end looks much like the cantaloupe I attempted to grow (and killed!) last year.

There are a few tomatoes in there. My nasturtiums are doing the best that they can, spreading to other areas that are not AS crowded. My poor blueberries are stunted. I went in this evening and trimmed out some of the squash/zucchini leaves so that they can get some sunlight.

So.

Long story short, I need help. What the heck are these? I can't tell if they're squash or zucchini, but whatever they are they are round and not elongated. Any thoughts?
Incidentally, the squash, zucchini and tomatoes I DID plant in the backyard raised bed are doing ok, but no where near as good as the ones in my Mystery Garden.

*This is a repost of a photo post I made at Facebook last night. Whatever. I still want to know what the danged things are!