Tony,

Thank you very much for showing how it's done.

I am going to order Ichi ki kei jiro and Tam Kam from Just Fruits and Exotics. They recommend these two for cold hardy and non-stringent type that I require. They'll be my first two persimmon next spring.

That's great Tony, I have ordered 3 Asian persimmons for spring planting. I will use this method to protect them in the first year or so.

Thanks so much for sharing this Tony.

A few questions for you... When in the spring do you know to remove the covering? Do the trees ever come out of dormancy too early and get damaged by a late frost? Have you had any trouble ripening those varieties, especially the Giant Hana Fuyu before cold weather comes?

Your system is proof that a good microclimate and winter protection can add probably two zones of hardiness... Makes me think about all the possibilities out there for doing this and why they are not more common.

Fn,
I removed the cover at the 3rd week of January when the weather a little milder and no more of that -10F. The weather still cold enough so no early budding. I have not had any late frost within 10 feet of the south wall of the house due to micro-climate and no North winds. This year was unsually warm and everything ripen at the end of September. On the normal year they all would ripen by the end of October. But I just let the persimmon fruits hung on the tree to the middle of November for ornamental purpose. I think this system can also work on other fruit trees out of your hardy zone if you desire to grow them.

Tony

Tonytran, Thanks for posting these interesting and helpful photos. You clearly have an eye for aesthetics and orderliness as your wrapped trees are not at all visually displeasing in your landscape as they could have the potential to be . I'm a little puzzled about the mechanism which allows the trees to be protected - that is, what is the heat source? Is it the decomposing leaves - I wouldn't think they would supply enough heat. Or is it merely enough for the insulation to moderate swings in temperature. When I construct similar (but much uglier) structures around vulnerable trees, I include land around the base of the tree within the enclosed space as my heat source. The land, albeit frozen, is considerably warmer than the air temperature, so heat transfer occurs from the land to the enclosed space.

Creek, the importance of having heat transfer from the ground varies from species to species. Given that Tony has had good results I expect the major need for persimmons is a moderation of temp swings and prevention of dessication from winds, not problems with the low temperature exposure. Dessication by wind is a huge deal, you don't want your tree freeze-dried! One sign of damage by dessication is the most exposed tips is what dies back; that fits with the cold damage I get on my Hachiya persimmon. On Pomegranates I have whole big shoots die, making me think dessication is less of a factor for them and low temps a bigger factor.

When I wrapped trees I always used aluminum bubble foil tents to get the ground heat. In tests I did, at 0F it was 15F under my tent and at -20F (which I don't get) it would probably be more like 5F under the tent: since the ground heat is constant, it helps more as it gets colder out.

Scott

I am in zone6b or 7 and i haven't done anything yet because most of the persimmon are still on the tree,but they are getting ripe.There leaves are still dark green.
I am not doing anything this winter,because i still want to find-out how coldhardy my tree's are.
Tony there was a mix-up in sion wood i got from forum members a few years back that turn-out wrong.I have to correct my whole group of 2 year-old grafted tree's.
I will notify you and send you sions free.
By the way you are doing a hell of a job with persimmon and others. I was like you one time with different types of fruits,i am slacking-of since i am at the age of building pine boxes.

Creek,
The water proof drape or tarp to block out the winds and rains. The dry leafs and shredded papers act as insulation. The only heat source is the on and off sun during the day that heat up the inside of the tree plus the benefit of the micro-climate of the house and no North winds.

I think Scott is right about desiccation of winds to the top branches of his Hachiya.

Persimmonbob, thank you for thinking of me. If you want to pass on your Kaki scionwoods then I will test them out and let you know how they turn out here in Omaha, NE.

Tony

There might also be a climatic factor that determines the importance of a heat source inside the covering, and that is daytime/nighttime temp swings. Tony's system would be least effective in places where the difference between day and night temps and winter solar radiation are minimal. Certainly it can't get any warmer under the covering than the daytime high IF there is no sun. But even if a covering simply reduces the duration of exposure to some low temp (it certainly does at least this) it can be very effective.

Obviously this method can only work with deciduous species, which makes it especially useful for folks in colder zones because there would be so many things to try that are just one or two zones more tender. But alas, once you start looking at the Mediterranean and subtropical species (adapted to zone 8 or warmer let's say) they're almost all evergreen and require a different setup.

Scott, you bring up some interesting speculative ideas regarding the nature of cold-hardiness in persimmons - that it's a matter of temperature swings and dessication. I believe these do play a part especially in early and late season situations, but like with most any other fruit there is a temperature at which the trees consistently sustain injury or death. From anecdotal reports of the most cold-hardy varieties of persimmons this number seems to be in the negative low teens Farenheit. If the survival of the plant were more dependent on the effects of dessication there would be observed a wider range of lethal temperatures to reflect varying relative humidities and wind speeds. Your observation of the different injury patterns between your persimmon and pomegranate I would attribute to the significant difference in cold hardiness between the two species in zone 7. On the other hand, if your speculation did prove correct, a simple measure to protect persimmon trees too large to wrap would be to ice coat them prior to the onset of dangerous temperatures.

But Tony's system works, at least so far, leaving the puzzling question of why. I think that it has mostly to do with modulating temperature nadirs. So if the outdoor temperature goes into the danger zone for a few hours, the insulating effects of the covering will prevent the tree from being exposed. I would be concerned that a weakness with this setup is that in the event of sustained temperatures say of below -12, the heat inside the enclosure would eventually be lost without replacement, inside and outside temperatures would equilibrate and the tree would be damaged or killed.

Tony, I had always wanted to grow persimmons. In the place where I stayed when I was a child, persimmon trees grow wild, they are everywhere. I just picked fruits off the tree for snack. Knowing there is a proven way to grow persimmon in zone 5. I am encouraged to try. Thanks so much .

Creekweb, you're so right that there is a specific temperature at which trees consistently sustain injury or death, but of course this also varies with several factors such as time of the winter, daytime highs, and even humidity levels (moisture content in the plant tissues), and most importantly: duration of cold.

Even if a certain tree consistently dies at -12 uncovered, I would not be at all surprised if it could survive an extended period that produced those same temps under a cover, simply due to the duration of cold factor. I'm not sure if I'm making any sense here, but I'm just guessing based on my experience and on what zone pushers are able to do with ornamental plants (which is really quite remarkable).

In some experiments I did with heavy rowcover wrapped many times around leaf-encased figs, I found the temperature inside and outside the cover was the same on the really cold mornings. That is why I don't think there is much temperature insulation effect. Most of the really cold temps occur in a relatively short period right as the sun is about to rise, and I had thought that the insulation would take the "edge off" of that but I didn't see it. I expect that Tony is doing better since his temps get much lower than mine - even the tree trunk itself will pull some heat from the ground up into the tree (the thermal conductivity of sap is 10-100 times that of air), and since his ground-air temperature difference is so high that sap can pull a lot more heat out of the ground than my trees can.

The way this could be tested is to drill a small hole in the trunk and put a thermoprobe on a wire into the trunk, running the probe cable outside of the covering, and then during cold periods compare the internal tree temperature with the outside (plus it would be good to have a third thermometer under the cover but not inside the tree). I have done many experiments with mounting thermometers and logging temps and I am always at least a bit surprised at what I observe.

Scott

Hey for the scientifically-minded see the link below, it goes into depth on the questions of thermal conductivity. It also points out the soil type and water content have an effect on how much heat deeper in the soil will make it higher up.

They also point to a study stating trunk wraps give up to 8C (14F) in temperature improvement, which makes me wonder if my row cover and leaves was not insulating well enough.

I made a rough calculation of heat transfer from the ground to the air assuming a tree was tented, compared to heat transfer coming up the trunk. I assumed a 4" diameter trunk and a 4'x4' tent on the tree. the 4x4' is 50 times the area cross-section of a 4" trunk. In looking up heat transfer differences, my wild guess is about a factor of 20 better for the sap/wood in the trunk vs the air, so that means the tree is 20 times better but 50 times worse, i.e. 40% of the heat transfer compared to the tent. So, this (very) rough calculation shows the heat coming up through the trunk to the plant can be nontrivial and is like "half a tent" more or less. This might explain why trunk wraps, if done with high-quality insulation, can help.

Scott

Here is a link that might be useful: review of frost protection

Scott, the problem with your model is that you assume an equivalence between heat transfer and heat conductivity, while in fact, conductivity is playing only a small part in the total heat transferred from the ground to the enclosure with most being transferred through convection. Air is a poor conductor of heat (this is the basis for double paned windows) but a good medium for convection. As air at ground level warms it rises and sets up currents within the enclosure -this is how the enclosure is primarily heated.

Creek, Indeed I forgot about convection, probably other stuff too since my thermo is 30 years rusted.

Another factor to counter that (which I also didn't think about) is the heat transferred up the trunk is already in the right spot where it is wanted, and the "20x" conductivity there could end up being similar to the heat flow rate via the air and then into higher branches - basically the conduction through the trunk could be similar to convection through the air.

Scott

Scott, Creekweb,
I was reading an article on winter protection. It stated that drying winds protection was very important because it could prevent winter burn and desiccation of branches. It also recommended to spray tree with anti-desiccant before wraps with insulation. In addition, I think micro-climate helped a great deal because the brick wall absorbing heat during sunny hour and radiated slowly during no sun hour to keep the temperature warmer within 6-8 ft from the wall. I think winds protection play a major role in Tony,s success.

I'm too much of a coward. I have Tam Kam, Patapsco, and Saijo. After about 4 years they are still in pots, and they winter at about 40-45 degrees in my garage.

I have my very first fruit almost ripe, one Tam Kam.

Scott, An in depth discussion of heat transfer is perhaps beyond what we should be discussing here, but my intuitive feel for the situation is that heat conduction plays a negligible part in total heat transfer in that part of the system above ground. Yes, conduction brings heat to the earth surface, but after that in heating the enclosure, it's primarily convection. One problem is that both the tree and the air are poor conductors of heat. Yes, the tree may be 20X the heat conductor that air is, but that's not saying much and in fact it acts more as an insulator than a conductor - to get an idea of the degrees of magnitude that we're talking about here, a metal stake can be 20000X the conductor that air is. There are other problems too with conductive heat flux, heat loss along the tree conductor and as you know the "warm" sap would not be flowing at these temperatures. Bottom line - in an enclosed gas environment without any significant conductors convection runs the show.

I was reading a response in the NAFEX "Richard Moyer and others is that for Zone 6/7, it is not the absolute winter minimum that kills kakis, but late spring freezes after the trees have broken dormancy. The great Easter Freeze of 2007 killed 10 out of 12 'cold hardy' kaki
cultivars I had, most of them 4-8 inches in diameter. The two that survived unscathed are 'Hira Tanenashi' and 'Sung Hui', only because neither had broken dormancy. We ate and sold many fruits from these
two trees this fall, until Christmas. Three nights of +19, 24 and 27F killed the other 10 'cold hardy' cultivars to the ground. In themountains of Korea, I observed huge, old kaki trees at Buddhist temples. So it's "not always how cold it gets, but how/when it get's cold", especially for some of these Asian plants we try to grow in the eastern US. Cliff England, at Nut Tree nursery in KY, also is trialing cold hardy kakis. Some of his material from northern Japan and north Korea".
So Tony, can I protect the hardy Asian persimmons wtih your method for short period from a late freeze in early April? Others comments are welcome. Thx.

To me, something else to think about is the type of rootstock when looking at when a tree breaks dormancy. Years ago, I bought a persimmon from Edible Landscape. It made suckers and I dug up about 10 of them and planted them in other places. The original tree, and the other 10 or so all break dormancy about 2 weeks before any other persimmon that I have. Doesn't matter if they are grafted with kaki or virginiana, they are always early.
I have rootstock that are 90 and 60 chromosome, and have not really paid attention to which one leafs out first, but my guess is that the 60's are earlier than the 90's.
Anyone have any observations on the differences between these two?

Benny

Good point to bring up in the context of this thread that in Eastern zones 6 and 7 kakis may more likely suffer temperature related injury or death from late spring frosts than from winter lows. Protective enclosures that include ground as a heat source/sink can moderate temperatures so they would not only protect from winter lows, but may also reduce the highs that can trigger the trees' early release from dormancy and so indirectly protect them from spring frosts.

Fruitcraz,

My plan to deal with late frost in April is to re-wrap the persimmon tree like I did in late fall. But this time, I will hang a 120 watts halogen light bulb in the center of the persimmon tree to keep temperature inside the wrap above the freezing point(30F) for the duration of the cold spell. I am glad my zone 5a allows me to trial Kaki persimmons and to do some of this experiment.

Tony

Thanks for all your inputs.

hey guys how are your persimmons doing?, will you and what protection this coming winter?