I know there are some older threads on this topic, but I’d love to hear people’s current zone-pushing success stories.
I’ve had a bay tree (Laurus nobilis) survive the past two winters outdoors in a small pot with no protection in zone 7, and it’s seen low single-digit temperatures multiple times. That alone is impressive—but it’s not the real zone-pushing story.
I took the plant as a division from my neighbor’s tree, which he says he planted shortly after moving in, sometime in the 1970s. That means the original tree survived unprotected for several decades in what was then zone 6, experiencing subzero temperatures multiple times. It’s planted in a raised concrete bed against a cinder block wall, but even so, its cold hardiness is pretty astonishing.
He also has two own-root Vitis vinifera grapes trained as small trees that appear to be about the same age and have endured the same conditions. He says he’s never had issues with pests or disease, either.
We had a pretty good cold hardiness test for tropicals this year in central Florida. Between my plants and my boss’s orchard, got a pretty good idea of what can survive here with acceptable damage on our coldest years, and little to no damage on our typical winters (which are usually a couple of high 20s days instead of mid/low 20s). I’ll list after a couple of weeks to see any lingering damages, but for an early glance, there are some promising species.
I also learned I can grow basically any tropical in an unheated greenhouse (at least as far as the cold goes). I had no issues with very cold sensative plants like soursop or cardamom other than a little too much humidity. Similarly, the high tunnels at work have kept everything mostly warm enough, and that aren’t even fully sealed on the bottom.
I am also zone pushing cold hardy plants southward. These are all still in the seedling stage however, so nothing to report yet. We are right on the edge of the native range for a lot of exciting fruit (pawpaw, american persimmon, chickasaw and flatwoods plums) so I plan on growing those (I have persimmon and pawpaw seedlings already and seeds of flatwoods plum). I also have some very northern plants that I am trying to grow out, but I’ll wait until they survive a summer (and wake up after a mild winter) before getting too excited.
My cumberland Rosemary didn’t even lose any leaves and stayed evergreen in a unprotected spot and it got down to -17°f, not the coldest, but they say they are semi deciduous if it gets cold enough.
My grapes, my himrod and Mars grapes had dieback, my glenora grape died, and the reliance and concord had no dieback whatsoever.
My che are fine.
All of my reds, pink, and one of my white currants all got toasted above the ground. My Primus white currant and all of my blacks have zero damage.
I have a Clivia that lives under my carport in a zone 9a/8b.It got bad damage last year because I left it in too open a place but surprisingly it came back. Also have a couple sensitive porch palms that are surviving on the porch near the propane heater discharge. And several yucca elephantipes that are doing very well in low temps throughout the years. They sneer at snow. Oh, and a navel orange, although I’m not sure if it’s going to make it this year. Had a hard frost a while back and it lost most of it’s leaves.
I’m not sure if these count or not, but I still have a pawpaw and quince growing here in SE Minnesota. The quince has fruited many times, tastes great right off the bush. Pawpaw hasn’t flowered yet but is taller than me by now.
Something that definitely didn’t work out here was American persimmon.
I came here to mention this same thing. Anyone doing reverse zone pushing?
I have a chickasaw plum that’s been in ground for a couple years now and is flowering currently. They are supposed to lose their leaves but mine has dropped some leaves but kept most of them both winters it’s been through so far. I also grafted scarlet beauty onto it so we’ll see how that goes.
I started some pawpaw seeds last year just put them in the ground a week ago. I have found a couple accounts of people fruiting pawpaw in this area but there is very little info on the prospect of this.
There are very low chill stone fruit varieties but nothing for pawpaw that I have found. In fact it doesn’t seem there is much known about specific chill requirements for pawpaws in general.
I am highly skeptically of pawpaws needing any true chill at all. They probably need a dormancy period, but that is different than chill hours. I have 3 dormant in the ground right now, so I will see how vigorous they are when they wake up. My last attempt at pawpaws had an armyworm eat the new growth in March and it definitely set the tree back. I also didn’t fertilize enough.
I know Neem Tree Farm in Brandon has a chickasaw plum that fruits. So it can be done. I am stratifying some flatwood plum seeds right now. I have been looking for chickasaw plants locally but they seem to be pretty rare and sell out quickly at the native plant society booth at plant sales when they have them.
We’ll see what my two pawpaws do this year now that they are in the ground.
I bought my Chickasaw Plum at The Nectary in Lakeland a couple years ago. They haven’t had any recently but they get them occasionally. If I see any I can let you know.
We are in a kind of awkward growing zone here, technically 10a but very close to 9b. Too warm/hot/humid/intense sun/not enough chill for most temperate things, but get borderline too cold for some subtropical things and definitely too cold for true tropical things without protection. Most years we get no freezing temps or just a couple brief nights just below freezing. This winter was a big exception where the whole peninsula got much colder than is typical but it does happen every 15-30 years or so. So growing a lot of tropicals is enticing because it’s possible and most years they do fine. You might get 20 years without any significant sub-freezing temps and have tropical get mature but at random you might occasionally get a winter like this that kills many things. You can grow peaches, plums, nectarines but only a small selection of very low chill cultivars. You can still grow strawberries but have to grow them in winter.
My strategy for zone pushing is this:
Start a lot of things that are marginal here from seed. Plant them in a few different spots and see what happens.
Grow fast growing/producing tropicals like banana and papaya. If cold takes them out you can replant and have fruit again within a year. Although, even in this rare extra cold winter the bananas didn’t even get frozen to the ground.
If something marginal for the climate does better than expected consider a grafted variety at that point.
This way I’m not out any signifcant amount of money when things don’t make it. In many cases the seeds are free and many are very cheap. My main exception is mangoes. I’m starting some from seed but I’m planting a few grafted dwarf cultivars that I can keep small enough to protect when we have a bad winter.
