For anyone who may be interested.
Loofah belongs to the botanical family of Cucurbitaceae, which means that it's similar to pumpkins and courgettes. In my opinion what is very important in growing pumpinks, courgettes and also loofah, is to plant them in a soil very rich in nutrients. The best thing to do would be use mature manure in quite huge amount. If you can't provide manure you could also use vegetable compost, which is easily produced starting from vegetable refuaes and even kitchen leftovers. I use to plant courgettes directly over a heal of compost.
Then, if you have a greenhouse, I think it's possible to grow loofah even in Canada. Don't forget that it is a climbing plant, so give it somethong to climb on!