Looks like squash or cucumber to me as well. Could be a seed was dropped by a bird or in compost. Since it is engulfing your wanted plants I say pull it out.

Do I need to pull the roots or can I just cut it at the ground?

should pull out rather easily ... ken

If it's still there, look for baby pumpkins forming. You can direct the vine tips and cut off individual leaves that are blocking too much light from other plants if you want to try to keep it. Will be killed by frost.

For future reference, there's a plant ID forum here too.

If you want whatever it is to make something you'll need to keep it well-watered. If it's pumpkin, squash, cucumber...feed it water often. Should be fun. Let us know what you get! Heidi

I am guessing it is a pumpkin, which makes sense since I had a pumpkin from Halloween that I threw in the general area last year. It is even bigger, wondering when it will fruit and how much damage it will do to the plants in that area.

We always throw our old pumpkins down into the copse every year...this year there is a pumpkin plant growing that is taking over the whole area. we counted 50 blooms and its wicked long. haven't watered or fertilized it once. we've been in a severe drought this summer.