Kārlis Taurenis wrote:Breeding hardy passifloras! Fascinating topic. Yet it seems imperative to get fully clear on passiflora hardiness to understand the implications.
Some of this is fairly contrary to my understanding. P.caerulea is sometime quoted as being hardy to zone 6 (-10°F or -24°C) but other sources such as PFAF - https://pfaf.org/User/plant.aspx?latinname=Passiflora+caerulea - state zone 9 (20°F or -7°C). A huge difference!!! What is the truth?
From seeing them only marginally surviving where I'm from in Southwest England, I'd say they're hardy to around zone 9 or probably zone 8 for well established specimens.
I'm not certain of the full range of P. caerulea, but I have seen well established plants thriving in Northern suburbs of Seattle, Washington, at least one of which was in a zone 7a spot. However, they reportedly only set fruit on years with either mild winters or early thaws.
