I have been pushing my zone for a few years now and although I have had many failures sometimes a nice surprise greets you. It is especially nice when that surprise did not require some of the gymnastic manipulations that are needed when pushing a zone.
A few years back I was engaged in a conversation here on the forum about increasing the hardiness of plums by grafting on Nanking cherry rootstock. I grafted a plum scion,given to me from a relative in a warmer zone where fruits are easy to grow, onto a Nanking bush. While the tree is very dwarfed it is doing pretty good with no particular protections or special treatment. The plum looks to be a European prune plum, definitely not one we can grow up here.
This year that plum produced fruit for the first time, only one plum but it was delicious. Processing: IMG_0302.jpegâŚ
Now I know that zone pushing can be very disappointing and is not profitable, I also have learned that although a zone pushed fruit tree can grow for a few years many times they succumb to winter damage and often die. Long term successes can be few but those that prove to be hardy are rewarding.
We are doing a very much more catastrophic version of that with a currently proposed U of F program to grow apple cultivars never before tried in Heat zones 9, 10 and 11. Basically they will grow or die. Hopefully a few will bear fruit. Of course it might result with 10-15 cultivars flushed down the toilet. But it should be an interesting trial in a bone fide research trial.
in your environment its almost your duty to zone push as you are really limited on what you can grow. what cultivars of apples do well there? before the 70âs we were a solid 3a. now a z4b. my reliance peach ripened its 1st single peach this summer. our last winter was like a z6 one. it was common to drive trucks all over the lakes here by early jan. not safe to do that in the last 4 yearsâŚ
The proven apples for me so far have been Sweet 16 , Chestnut and Trailman, along with the standard apples that will survive here. Wickson crab has survived for four years with no dieback yet, but also no fruit, the same with Honey Gold and State Fair. These apples are outside, along with the prune plum I talked about in my initial post.
I have a greenhouse that is unheated in the winter months, and the temps. In there are the same as those outside in the winter. I have various plums, pears and apricot planted in the greenhouse and have had zero dieback on
Mirabelle, Green Gage, Golden Gage plums, Flemish Beauty, Dew Drop pears and Coxs Orange Pippin, Golden Russet, Cortland apples.
The ones that have fruited so far for me are the Mirabelle, green gage plums. No blossoms yet on all the others except the Dew Drop pear that has bloomed the last two years but I have no other pollinator for it. I am looking for pear pollen next year.
My theory why these trees do not die back is that although the temperature in there reach the night time lows outside, even in the dead of winter the sun does increase it during the day so the overall length of time the trees are at a temp as low as -40C or lower is considerably less.
No scientific evidence for this though, just looking for a reason why.
ETA my seedless table grapes for zone 4 absolutely love my greenhouse and produce buckets of grapes. They are layed down in the winter and I bring in snow to keep them covered,
A friend with a large greenhouse with mostly stone fruit has had issues of varying types when dormancy is over and warming of the trees starts.
My observation has been that bringing trees out of dormancy rapidly creates many problems.
As a reptile breeder the same goes for bringing snakes out of hibernation/brumation too fast.
Slowly warming the day and night time air and soil temperature alleviates these problems.
It takes aproxx. 2 weeks of gradually raising temperatures to acclimate the trees just lime a natural process.
Ive also observed trees regardless whether they are temperate,sub tropical,tropical,or ultra tropical prefer 85°F as a.maximum temperature and anything above that is when they go into hyper mode of transpiration and start showing signs of heat stress.
Even though they can handle higher temperatures,and consistently,higher quality fruit is always produced when extreme temperatures can be avoided.
Any opinions on my observations would be appreciated.
This part is an important observation. Iâve noticed that some things I push get winter damage but still get a little larger each year than they did the year before. Other things regrow each year, but with decreasing health and vigor until one spring they are gone. So âit survived!â isnât good enough if it cannot recover enough to also continue growing larger with each passing year.
P.S. I love the name Ursula! Thatâs our daughterâs name
I donât have that problem. Up here once the winter sets in that seems to be it. We donât get very long winter warm spells and the days are so short with the sun low and weak on the horizon that winter warm ups resulting in early bud break donât exist yet. I do nothing for protection in the greenhouse except to take advantage of the deep snow pack to shovel it in the green house covering the roots. Our biggest winter kill comes when the weather drops to -30C before the snow comes. In that scenario the roots seem to suffer. So banking up snow over the tree roots seems to be the best course of action for me.
for it to work here i would have to partially cover the greenhouse as well as shovel snow in. we do occasionally get -40 here but its rare and lately -20 is rare. we are starting to see some around freezing to just above during jan. - mar in daytime which would probably bring the greenhouse to 10-15c which wouldnât be good for dormancy.
Yup the warming with the sun was what stopped me from doing this for three years. For the first winter I draped white sheets on the trees but then I just stopped and it didnât seem to matter. But for others where it is warmer it might not work. Another consideration is that I planted self pollinating plums, but the other fruits do need to be hand pollinated as the snow is still on the ground when they blossom.
We each know our own area and have to pick what works for us. Watching where the snow builds up is a big part of that in a zone such as mine.
I noticed that the snow slid off the rounded greenhouse roof and piled 4 feet deep. I took advantage of that and planted zone 4 gooseberries there where they would be covered with this snow. This year they produced some lovely large berries.
We have an outside boiler and that is a great source of underground heat. I am careful not to plants trees or perennials over the boiler line that goes to the house but I do have a patch of tilled ground over it which makes a great spring garden. A few hoops, some plastic and I can plant cool weather crops such as lettuce when the temps are well below zero and there is still snow on the ground.
Making use of special conditions in my yard is the only way I can push the zone.
Trailman is bulletproof in Fairbanks, Alaska. Chestnut dies back in a cold year. Sweet 16 and State Fair winterkilled. Our cold temps can last; one year it didnât get above -40 for nine days.
Probably keeping snow cover inside the greenhouse also helps to keep the overall temps from rising too quickly. Seems like a lot of heavy work though, as you refer to the gymnastics of zone pushing. Here in Vermont,and on the east coast in general, it seems that warming winters are coming more quickly. I laugh that the USDA has finally put us in zone 5 when Iâve been seeing zone 6 for several years, and last winter was zone7 for a the coldest nights. That doesnât mean that things are better though. It just means things have to endure more extreme swings. All the trees this year bloomed , and we got a very late frost in May. Sort of like last year when all the fruit was frosted out, and even Georgia lost their peach crop.
You have the same temps as we do. Because we are central Canada we can get -40C for a couple of weeks as well. Coldest I remember was -50C, nothing moves at that temperature the word is absolutely silent.
Sweet 16, State Fair, Honey Gold and Chestnut have suffered some dieback but I do multiple stems to mitigate total death so it is very rarely that all have dieback, I always have two stems that donât have any so the tree still does pretty good.
Moving the snow is not that bad. I have a large push scoop shovel and I have to do the driveway right next to it anyway. I just scoop and push it up a small ramp into the house and dump. A half hour a day for two days finishes the job, and I add thru the winter if I feel like it.
The exercise is good for me or I would sit to much
Iâm very much in agreement because I also use a push scoop. I do my driveway with it. My driveway is about 800 feet long and most of it is very steep. Great exercise! But as I said above, itâs getting warmer fast so I only need to clear the drive a few times a year now.
Thanks for the compliment