I was a bit worried about my watermelons this year as they had spread out in all directions, looked extremely healthy, and had nothing but male flowers. Then almost overnite they were loaded down with tiny melons. Depending upon your planting date they may be ok and just a bit late. On the other hand my cantaloupes set fruits early on and are now large and very close to turning orange. As long as the gumball tree isn't shading them too much and it's roots aren't undermining them they should produce.

Assuming you know the difference between male and female blooms and you have both you can always try some hand pollinating. Otherwise all you can do is make sure the plants aren't stressed in any way - pests, evough sun, enough but not too much water, enough nutrients, etc. - and then be patient.

Dave

Not sure where you are, or when your melons started blooming, but quite often a plant will first produce loads of male flowers (and less frequently, a load of female flowers) and nothin' happens. As Dave said, it would be smart to recognize the difference, and just do hand pollination if it doesn't happen naturally. About half of my melons are the result of hand pollination.