This is an amazing thread, Scott. Keep us posted. Just incredible you can do this in Mass.

Scott, you are on a different level literally and figuratively ! I am using the barrels for heat but I don't want to break dormancy. So you might be right that I don't Need 95% efficiency . The only black rubbery roofing stuff that I know of would be way too messy. I try to leave my high tunnel open as much as possible in the winter. We can have really weird temperature swings. If I break dormancy I am prepared for the worse possible seenario. 80 * F one day and maybe 20 * F in a week or ten days.....You are doing awesome things where you live. Great thread ! Tom

Tom, since you are in central Alabama, I bet the plain white barrels will work fine. I doubt it will ever even get cold enough to have any of the water inside freeze. Mine probably have a 3-4 inch thick layer of ice in them right now!

Also, due to the high heat capacity of water, the water barrels could help cool the inside of your high tunnel on a warm day if they were not painted black. Although you probably only would see a deg. or two of cooling effect since you have a high tunnel w/ a huge interior volume (compared to my setup). To get a larger effect, you would probably need a very large number of water barrels.

The thermal mass of the water barrels will in effect serve to even out the overall temperature swings, reducing the magnitude of the temp. swings both in a positive and negative direction.


Here's a graph showing exactly this effect from Dec. in my enclosure.


Best of luck,
-Scott

great protection Scott. My protection is not that great. We dropped to -0.9F (-18.3C) outside and the temperature inside my Citrumelo (Dustan) protection likely dropped below 10F (-12C) since I was monitoring the temperature inside my Yucca carnerosana protection which dropped to 11F (-11C) and it had a heating cable inside! The Citrumelo protection used a string of small christmas lights and a 40Watt light bulb. The Citrumelo still looks OK.

I took a photo of the Citrumelo this morning:


Yucca carnerosana looks good too!


For comparison my Monkey Puzzle tree (Araucaria araucana) has some minor burning:


A small Eucalyptus debeuzevillei has some burn too....this Euc seed was collected in the coldest areas of it's range.

Tim, Monkey Puzzles get huge, don't they? Will it tolerate more cold when it get's larger or will you build larger and larger enclosures?

Well, passive protection will never do ...
It cools out till you have the damage.

If you would have put some light bulbs and a thermostate, all would have been just fine.

Tim, hopefully the Citrumelo will pull through, maybe with some defoliation. I've been thinking of trying a Monkey Puzzle tree myself, but currently do not have anywhere to put it.

Greg, I doubt you would ever have to worry about a MP tree getting huge in New England. You can buy them at Sylvan Nursery down in Westport, MA. According to a Plantsman there, the largest they are aware of in MA is about 10-15 ft tall out in Chatham (in a zone 7a/7b area).

Sanguinello, that is complete Hogwash! You should clearly state that this is only your Opinion. Sepp Holzer's citrus trees make it through the winter with only passive protection in the Alps, right?
It is 100% possible to protect a citrus tree in New England with only passive protection. I believe that this thread good example (at least it is so far).

Here is a quick preview to the update I will post after the end of the month:

Outside Weather:
1. From Jan 20 to Jan 29 the outside temp did not rise above 32F (0C) for 208 consecutive hours (8.5 days)
2. From Jan 22 to Jan 28 the outside low temps were 14F (-10C), 7F (-13.9C), 3F (-16.1C), 8F (-13.3C), 12F (-11.1C), 14F (-10C), and 18F (-7.8C). This is typical of an average winter in the Boston, MA area.
3. On the coldest days (Jan 23 and 24), the average temps for the entire days were 11.7F (-11.3C), and 10.9F (-11.7C), respectively.

Inside my citrus enclosure (with Zero supplemental heating, although I do have an electric heat source for emergencies):
1. There is currently no evidence of any damage to my Satsuma
2. The lowest temperature recorded inside the enclosure was 27.6F (-2.4C) on Jan 23.
3. The largest temperature differential between inside and outside was 24.2F (13.4C). This is nearly 2.5 full USDA climate zones.

Of course you can bring it through ...
What I meant was without damages ...

I understand your point, but... from my previous post:

"1. There is currently no evidence of any damage to my Satsuma "

...and my passive protection is not even close to the ideal setup. There are several gaps (probably at least 30) in the walls where warm air from inside can freely leak out, I get a huge amount of radiative heat loss from the glass roof panel during the night, etc...

Tim,
I also think that Dunstan will be fine.
From my experience when temperatures are lower than -12°C the airtight styrofoam protection without active heating is much more efficient than the cage/geotextile fabric.

I hope my Citrumelo survives...........I'll update everyone in a few weeks when winter is over.

I heard there is a Monkey Puzzle tree out on Cape Cod, MA.......other than that..........I've never seen one planted outside.......except mine. I've seen the MP's at Sylvan Nursery and asked them where they are planting them so I can see them............they didn't know of any specimens outside...........but they had 5 or 6 of them for sale.

My MP gets winter burn a lot. Here's what it looked like after the 2009 winter.


Here's a photo when young.........in 2006.


I started protecting the MP after the 2008-2009 winter since it was so brown......it's buried under the mini greenhouse.


This season I didn't protect it............probably should have.

Here's an update on the Early St. Ann Satsuma after the first round of true winter weather this past Jan.

Outside Temperature Notes:

1. From 1/17 to 1/29 the temperature was above freezing for 39 of 280 total hours (11.5 days).
2. From 1/20 to 1/29 the temperature was at or below freezing for 208 consecutive hours (8.5 days).
3. From Jan 22 to Jan 28 the outside low temps were 14F (-10C), 7F (-13.9C), 3F (-16.1C), 8F (-13.3C), 12F (-11.1C), 14F (-10C), and 18F (-7.8C). This is typical of an average winter in the Boston, MA area.
4. On the coldest days (Jan 23 and 24), the average temps for the entire days were 11.7F (-11.3C), and 10.9F (-11.7C), respectively.
5. The high temperature on 1/23 only reached 17F (-8.3C).


Inside Temperatures and Notes:

1. Except for on Jan. 1, when I was testing my emergency supplemental electric heating system, the interior temperature was regulated by passive means (i.e. from 1/2 to 1/31 no supplemental heat was provided).
2. There is currently no evidence of any damage to my Satsuma
3. The lowest temperature recorded inside the enclosure was 27.6F (-2.4C) on Jan 23. (This was measured approx. 6 inches below the glass roof, the remote temp sensor can be seen in one of the images below)
4. The temperature was below 28.0F (-2.2C) for a total of 2.5 hours the entire month.
5. The temperature was between 28.0F (-2.2C) and 32.0F (0C) for 98 total hours during the entire month. (From the scientific literature, temperatures in this range should not result in much, if any damage to healthy, cold-acclimated citrus trees)
6. On two days, the average interior temperature was below 32F. On 1/23 and 1/24, the average temps were 31.5F (-0.3C) and 31.4F (-0.3C), respectively.
7. The soil temperature dropped from 43.8F (6.6C) to 36.5F (2.5C) during the cold snap beginning on 1/17. After 2 days of warmer weather (1/30 and 1/31) the soil temperature rebounded to 40.6F (4.8C). The outside low soil temp for Boston during the cold snap was 17F (-8.3C). Soil temps were measured at a depth of 4-6 inches (10-15 cm).
8. The largest temperature differential between inside and outside was 24.2F (13.4C). This is nearly 2.5 full USDA climate zones.
9. An approximately 4 inch (10 cm) layer of ice formed in the water barrels making up the exterior of the structure. The heat released during the freezing process of the water is the primary reason the interior temperature did not drop to more than 4F (2.2C) below freezing on the coldest days. The exact same phenomenon is what microsprinkler systems rely on to protect citrus from freezing weather in citrus growing regions.
10. On the coldest few days, I put 1" thick pink foam board insulation on top of the glass roof at night to minimize radiative heat loss.


With any luck, the cold weather in the last half of Jan. was the coldest we will see this winter in MA. The current NWS forecast has typical winter temps (highs in the 30's and lows in the mid 20's) for the next week or so. After that, the long range weather models seem to indicate things will begin warming up with above average temps expected: http://www.cpc.ncep.noaa.gov/products/predictions/long_range/seasonal.php?lead=1

Tree in the enclosure:


Sample leaves (top from old growth flush; bottom from last growth flush in Aug/Sept)

Good work

I would try Sudachi, it is harvested green in late Aug or early Sept. Very cool citrus.

great graphs and temp data. How much, if any, ice formed in your containers during the cold period? A low of 28F is amazing.

What will you do next season when your citrus are 2' taller.