I have just visited the National Plant Collection of Passiflora cultivars at Tynings in North Somerset, and come away with my very own Passiflora edulis. A great number of the passion flowers produce edible fruits, so says Jane Lindsay, who holds the collection, but edulis is the sweetest and tastiest. It ain’t the prettiest, not by a long way, but with a bit of luck it will produce me some of my very own passion fruit (each flower only lasts for one day, and so this one fertilised at the nursery is now on its way to becoming a fruit).
Handily, this edible one happens to fall into the category grow in a cool greenhouse. Some (but not many) are fully hardy and can be planted outside, other (quite a few) are stovehouse or conservatory plants, and need heat all year round. But the vast majority need a little protection in winter, but wont take well to the extreme heat of a conservatory. In fact, the ideal thing to do with passion flowers such as mine is to keep them in a cool greenhouse in winter and then move them out into the garden in summer, but I guess this get less likely to happen as plants grow.
When I told Jane that I didn’t heat my greenhouse at all, she didn’t seem worried. The main thing is to take care of the roots. You must keep passion flowers on the dry side over winter, but also never overpot them. If you do you’ll get lots of top growth before the roots have developed, and that leaves the plant vulnerable to the cold. I’m still not convinced I can pull it off. This is exactly the class of plants that I seem to kill off in my greenhouse year on year, but blind optimism seems to be a prerequisite in gardeners, particularly those of us that are still trying to grow semi-hardy plants, after the last two winters had. This year’s bound to be different, eh?