Passiflora seedling development

Hello all. Being a passion flower lover I decided to stop cheating by buying plants and instead growing my own! Though frustratingly slow to germinate I've now got about 6 shooting up (and about 20 being rather lazy and seemingly content with one true leaf), putting out new leaves every 4/5 days! They're different species and all but one are supporting themselves perfectly well. But the other one is too tall to support itself but isn't throwing out any tendrils. So my question is - should I stake it, or would this stop it producing any tendrils (due to some biochemical signal or something!!!)? Or should I let it droop as this may induce it to throw out a tendril, thus becoming self-supporting? Any advice would be greatly appreciated. Thanks!!

 

Passiflora seedlings produce tendrils once they become adult, ie start producing adult leaves.
A small split cane and a piece of string tied very carefully will keep the plant growing straight and not affect tendril production once the plant reaches that stage in its development.:WINK1:

 

Much obliged, thank you. Roll on spring and some vigorous growth!