I had this problem last year with pumpkins (and probably will again this year to some extent).

I ended up aggressively trimming vines, and I don't think I really noticed any real negative effects to the plants (other than obviously not having those vines available to grow fruit).

Big trouble in little China when planting 2 long season vining crops close together. When I plant my melons I plant short season crops around them (like beets, spinach, broccoli, bush beans, lettuce) so that they can be pulled out before the melon vines reach the space they took up.

At this point all you can do is trim back the vines and keep trimming them back as needed. Next time allow any vining crops much more space or construct trellis for them to go up. Like vgkg says plant only short season crops near them.

Dave

I thought of trellising, but wouldn't a pumpkin or melon break off under its own weight?

The battle of the vines begins!

There was a bit of a debate a while back over whether a melon or pumpkin could support its own weight on a trellis. Both sides presented photo evidence supporting both the pro and con. It seems to come down to individual conditions. Smaller fruits seem fine. Larger fruits sometimes do fine, and especially depending on environmental conditions (storms, high winds, failing trellis...) sometimes not.

To avoid the larger fruits (or smaller ones if desired) from breaking off, there are many materials that can be used to make a 'sling' for the fruit to hang in. Basically, any material that provides a bit of airflow and dries out readily will work.

I purposefully planted sweet potatoes and melons on opposite ends of an 18' bed. They are beginning to meet in the middle. My solution... let it grow! Lol.

One of my pumpkins is a Dill's Atlantic Giant...

Are you limiting the Dill's to one fruit per plant - common for people who are growing the variety for what it's bred for... size? If so, then let the fruit stay on the ground, and let the rest climb. Pinch off all the female flowers on the trellis, and that will help the pumpkins on the ground reach their potential.

The recommendation for Dill's is more than 70 sq. ft. per plant (not hill.) I'm sorry to be so blunt, but you couldn't have expected no problems.

There is one Dill's, one Polar Bear, and one generic that my kids grew from last years jack o lantern. The area is probably about 100 square feet total in their designated bed, but my initial plan was to let the vines colonize where the onions and broccoli are, since the broccoli is done and the onions close...but they seem to want to go the other direction.

Plus, I stuck my tomatoes between those two areas...assuming they could go around and through them...but if they do that, I can't get to my tomatoes!

Slightly different scenario, but one of the beds I used for tomatoes this year had 4 of the hardier plants of Swiss chard from last year which I left grow for seed. The chard bolted 6' - 7' tall and fell over into the tomatoes. It was a bit of a mess, with one pathway being completely blocked. To top it off... all the chard plants turned out to be males. No seeds. :-( Such is life.

Looks familiar. My Tahitian Melon squash are invading my cantaloupes. One leaf of the former will shade a half dozen of the latter.

I read the 70 sq ft recommendation and figured I was OK. The whole garden is 40 x 45 or so...

Do the "smaller" (maybe "less huge") giant pumpkins like Prizewinner and Big Moose have the same requirements?

I plant both cantaloupe and watermelon. My garden is roughly 25 x 50. I count on the melons taking up half of the space by the end of the season and I do my best to plan for it. Peas, lettuce, radishes, spinach, etc have come out already where the melons are now sprawling. I need to get some carrots out of the way because they're about to be overrun by the 'loupes. I possibly messed up by allowing 3 plants of each to grow. The last couple of years I've limited to 2 each and that was plenty. I know by the end of the year, I'll have melon vines reaching beyond their allotted space of 625 square feet.

I say trellis (vertically) and tie useless extra pantyhose to take the weight off plant. Shove melons in pantyhose! Seriously! Keeps the ants away from the melons also.

@vgkg - Aren't watermelon in hot weather while beets, spinach, broccoli, and lettuce in cold weather?

Bobby A, that is correct as in spring v summer plants. I plant the melon transplants in mid May while the earlier crops are still growing nearby and around them. By the time mid June arrives the melons are starting to vine outward as the early crops have peaked and are being removed making room for the melons vines to expand.