@Richard just made the mistake of asking me in this thread what kind of things I would grow if I were in zone 9b, like he is.
Muah ha ha ha ha! (Rubs hands together gleefully.) I’m in zone 7b, and there are LOADS of things I would plant here if I thought I could get away with it! (In fact, most of the things on the zone 8 list and many of the things on the zone 9 list, I’m planning to try in a greenhouse.)
Here’s a very incomplete and totally subjective list!
Zone 8 perennials:
Feijoa
Strawberry tree, a.k.a. Jamaican cherry (Muntingia calabura)
Yacon
Yucca aloifolia (edible fruit that tastes like a cross between blueberries and molasses)
Texas persimmon
Longan
Loquat
Zone 9 perennials:
Ice cream bean
Saigon cinnamon (apparently the fruit can be eaten, too!)
Ugniberry / Chilean guava (Ugni molinae)
Miracle fruit
Mashua
African potato mint
Cherimoya
Yumberry (Myrica rubra)
Roselle hibiscus
Jojoba
Manuka (mainly if I had bees, so I could harvest my own manuka honey)
Carob
Zone 10 perennials: (in case you have nice microclimates to put them in, or are willing to wrap blankets around them in winter for extra cold protection)
Barbados cherry
Sin Espinas dragonfruit (it’s the only thornless dragonfruit variety)
Black sapote
White sapote
Rose apple (and other syzigiums, like lilly pilly)
Eggfruit
Olosapo
Epiphyllium (it’s a thornless cactus that grows edible fruits that taste like a cross between dragonfruit and passionfruit, with gorgeous flowers)
Sapodilla
Custard apple
Serendipity berry (Dioscoreophyllum cumminsii)
Yeheb (Cordeauxia edulis)
Peanut butter plant
Starfruit
And here’s a list of banana varieties, specifically:
Dwarf Orinoco banana (zone 7a – I plan to get one eventually)
Dwarf Namwah banana (zone 7b – I have one )
Ice Cream / Blue Java banana (zone 8)
Misi Luki / Mysore / Pisang Ceylon / Pisang Keling banana (zone 8)
Raja Puri banana (zone 8)
Thousand Fingers banana (zone 8)
Ae Ae banana (zone 8)
Cavendish banana (zone 10 – this is the cultivar sold in grocery stores)
Double Mahoi banana (zone 10)
Gros Michel banana (zone 11 – this is the cultivar that USED to be sold in grocery stores, and is supposed to have tasted better, and is now commercially extinct)
There are loads of banana varieties that are hardy to zones 9 and 10 that you can look into. The three I listed are the only ones I know off the top of my head. I haven’t researched those as much because I’m trying to find ones that can grow for me.
I bet a lot of other people could chime in with things they’d love to grow if they lived in zone 9! I imagine avocados and mangos would be top of the list.
One project you might try is to plant seeds of the least hardy perennials in less and less favorable microclimates, and/or at the “wrong” time of year, and see what survives. Then you could send seeds (or seedlings) to other people near you who live in slightly colder zones, and see if those plants will grow for them.