Progressive cold hardening is the idea of breeding plants to be more cold hardy by planting a amounts of seed in a location that is slightly colder than the parent plant could be reliably grown in and selecting the offspring that performs the best and save seeds from it and repeat the process.
It really can be done in other directions too; if most years you don’t have long enough or cold enough winters, or any plant that can grow to some degree for some years but not thrive( like has drought, heat, wet, wind, or soil ph problems).
I would like to ask anyone who has time and space who zone pushes or wants to, or has anything that gets cold damage on the colder winters to plant out a bunch of seeds to try improving them to be more cold hardy .
im doing this with persimmons and Dunstan chestnuts i grew from seed. 1 got 9 chestnuts and 24 persimmons. ill keep you posted how they do. since we moved up half a zone there’s a good chance most will make it.
I’m already trying trifoliate orange, wanting to graft some poncirus plus to the trees I already have and use it in breeding more cold hardy ones. I would like to try planting a bunch of seeds of each: figs (probably a few generations), creeping raspberry, blue sausage tree, chocolate vine, toon tree, maypop, sichuan pepper, raisin tree, and pistachio. Maybe some pomegranate too, possibly a few generations, but that wouldn’t be expected to grow without protection even in a warmer spot for most of all the breeding process. I’ll try getting them to take my winters well (-25°f- -30°f) then pass them on to whoever wants some.
I bought an ultra-freezer that I’m planning to use for cold-hardiness testing with my breeding projects. It gets down to -47* F and can be set to other temperatures. It would be easy to use to kill off less-hardy seedlings so that only the hardiest survive and get selected for breeding future generations.
Thats interesting idea. I was wondering if something would work like a walk in cooler or freezer like what we had at the kitchen i used to work at.
Is there any way to diy a heat tolerance greenhouse? I would like to have higher heat and drought tolerance with cold hardiness because our area seems to be having on average warmer winters but a very cold spike the last few winters.
I think that most greenhouse set ups use ventilation to avoid getting too hot in full sun. If you are going for very high heat tolerance you could just not ventilate well.
I’ve been pretty busy as of late, but I’m slowly working on the same idea with figs and pomegranates. I’m in Zone 5b in Eastern Canada. I’ll hopefully have some results to discuss in a few years.
good luck. Pushing zones requires very large numbers of seedlings to have a reasonable chance of success. IIRC, apricots were pushed north a full zone by planting about 3500 plants of which 4 survived.
That’s a lot more seedlings than I was planning of trying per planting, like for the figs I was thinking just a couple hundred to a thousand seedlings, but I guess I was planning a few generations. With a few generations of figs with a few hundred per generation selecting for cold hardiness, how much of a improvement do you think would be possible?