Wild Cucumber (Echinocystis lobata) aka wild balsam apple
Blooming now over most of southern Ontario, rapid-growing wild cucumber vines grow along fence lines, at the edge of woods and in lowland areas. The fruit looks sort of like a prickly cucumber. (It's not edible, though! At least I don't believe it is.)
The green spikes to the right of the the wild cucumber - ahh-choo! - are ragweed flowers (Yep those are flowers). Ragweed's pollen when blown in the wind causes hay fever.
Wild cucumber climbs up then cascades down this tree trunk
The vine grows to 5 metres (17 feet) long, covering everything in it's path
If you love flowers -- and who doesn't - check out Today's Flowers at http://flowersfromtoday.blogspot.com/