Hey Kirly. I grow pumpkin and watermelon every year. It depends which type you're growing
as to how big it gets. A radius of anywhere from 6 foot to 20 foot. The soil needs to be welldrained, full of organic matter, esp compost and/or well rotted manures and mulched to maintain constant soil moisture. Once they get growing
they're pretty bulletproof. If you pinch out the main growth tips it will encourage more lateral growth and this in turn will encourage more female flowers
. It's not that hard to re-route a tendril which is going the wrong way but they can be a bit brittle so be carefull. Some members of the cucurbit family can cross pollinate so best not to have two different varieties intermingled. A bed of 10 foot square will accomodate most pumpkin and watermelon. If you have one for the pumpkin with 2 or 3 plants
in it and same for the melon you'll be fine. plant
in each clump and thin out to the strongest one once they get going. When the vine is finished, it's a great additive for a compost bin. Really gets the heat into it. Run over the vine with a lawnmower to make it easier to compost. Hope this answers your questions.