Could you maybe mean an acorn squash? If you could be more descriptive that would be very helpful. I could see acorns being considered round and they are deep green like a standard zucchini. Also the seeds are very common wherever vegetable seeds are sold. Most squash are very prolific if given the right conditions. It is not uncommon for the vines to grow a foot per day during the peak of their growth.

Are you talking about the red leaved cannas? My basement is always full of boxes of cannas every year. They are indispensable in my garden.

I think something with a yellow or orange fruit would look nice. Like a small pumpkin (jack-be-little or wee-be-little) or an ornamental gourd (bicolor pear or small spoon)

I've found most squashes don't do well trellised. One notable exception is the Tromboncino squash which actually does better on a trellis. It also has great novelty value as well as producing a very useful crop.
http://www.territorialseed.com/product/1100/220

Yes, it must be acorn squash that I planted. I don't know how I could have been so busy that I don't even know what I purchased or planted (though it was done as an after-thought on impulse). The vine is almost a thug! I am having to "save" my glads, and anything else within 10 foot striking distance from strangulation - and the summer is young!

My cannas are very tall variety with green leaves but red flowers. I am thinking something with orange or yellow fruit would be nice to trellis - or just even the flowers on the vines.

Unfortunately, my favorite cannas (president) didn't store well in the basement and I had none - but tons of these others. I do have varigated leaved Lady Di's this year and will see how that works this winter. But the ones in question are very tall and green leafed.

I will also look up trombocino squash and see what that is like when I have more time tonight.

Thanks for the suggestions!