creating microclimates for cold-sensitive plants

[philip]

Hello all,
i am getting increasingly interested in creating microclimates in order to grow cold-sensitive, heat-loving plants.
Most of us living in the northern hemisphere probably could make a list of plants that they cannot grow under normal circumstances
because they live in a place one or two climate zones too low (avocado, citrus, feijoa etc...)
I would like to learn more about different ways of creating microclimates.
Aside from the obvious "south facing wall", "south facing slope" and "using a water pond to reflect additional light" like you find mentioned in books i would like to find more in depth information explaining the concept. I searched and found very little on the internet.
Sepp Holzer comes to mind for example who manages to grow Kiwis,Citrus and other exotic plants outside at 2000 meters elevation in the alps.
I have used 5 Liter water gallons placed in a circle around young cold-sensitive plants with great success.
The ideal methods would involve only natural materials and no plastic if possible.
I understand the basics but i reckon there is a lot more to know.
Has anyone here experimented with creating microclimates or knows an internet source explaining methods more clearly?

[imgrimmer]

a dry sandy soil can help to raise temperatures earlier in spring and are warmer in summer. a lot of southern plants are said to like it dry in winter too.
Here around Lüneburg soil is very sandy and dry. summer is always warmer and more comfortable than e.g. in Hamburg only half an hour away with more swamp like soil.
a good drainage could be maybe a good help too.

[prairiegarden]

How many zones difference do you want to accomplish? Sepp has very steep slopes to deal with and my understanding is that he uses natural rock faces the way other people use the walls of their houses, or you used your water bottles, like a natural heat sink.

It's not just cold you have to be concerned about it's also the wind. IIRC half a mile or so into a forest there is no wind, the trees buffer it into non existence. Most of us don't have a half a mile to play with but designed shelterbelts work very very well even if they aren't half a mile wide.

One thing to consider is the frost free days, even if the plant can cope with the cold, it may not bear fruit or even flower if it doesn't stay warm enough for long enough.  I had started some grapefruit trees and then found out that there is absolutely no way they would ever bear edible fruit in this climate, the fruit takes too long and requires too many heat units to mature.  Light is another question.

The British in the 19th century went in for brick walled gardens and conservatories in a big way and had wonderful gardens with fruit trees espaliered on the brick walls, for example. but even they kept their citrus in greenhouses or conservatories. Sepp is a very unusual man.. and I'm not sure that any of his citrus actually has borne fruit even though the trees have lived and flowered. There are cold  tolerant versions of many tropical or semi tropical plants now, but cold tolerant is a relative thing.

Are you familiar with  a book called Paradise Lot? a couple of guys from Boston who are growing all sorts of stuff in  ( or near) Boston, including bananas although only the leaves of those are edible, not the fruit. Might be some useful info in there..

[mountaindweller]

Or the fruit tastes awful. Oranges here simply don't get the real taste. And the snowload. Evergreen trees are not designed for snow load. I had a feijoa snapping completely under the snow. Another was cut in half.

mountainherbs.net/

[philip]

We don't get much snow here. Of course there are limits to everything but a lot of people who tried and failed either chose the wrong variety and/or didn't pick a sheltered spot.

If you ask people around here whether you can grow melons or even watermelons outdoors they'll all say "no way" but i managed to do it last year, so the ones who had

tried before probably just used seeds from shop-bought fruit. Hybrids adapted to warm countries. Of course that won't work.


The place you live in and its climate dictates more or less what you can grow and what not. I think you could probably make up for one climate zone by creating a microclimate, not more (grow a zone 10 plant in zone 9 etc...)


The lack of sun and warmth is an issue but to have the plant make seeds is what counts. If a feijoa was to produce fruit with viable seed and that seed was grown out again,

some of the offspring would probably make tastier fruit then.

This is what they did with the northern pecan nut trees that grow in Canada now. They chose germplasm from the farthest north populations, crossed, grew the seeds and selected and now there is pecans growing further north than ever before.

[templeton]

A consideration would be whether single events or prolonged periods are the issue.
I've read about the soil temperature difference made by using raised beds running east west, i think. the front of the bed facing the sun warms up the soil - only good for annual crops, probably. I live on a hillside, and use permanent raised beds made from railway sleepers (ties) that face mostly north (southern hemisphere).

A really important consideration here is air drainage - cold air flows down a very small valley next to my house, and my backyard is protected by vegetation and wooden fences that divert cool air flowing down the slope from entering my garden, and the fact that there is somewhere for the cool air to drain toward. Surrounding trees are also protective, I think. The difference in temperature is remarkable - on cold mornings good frost on the ground next door, and hardly any frost in my backyard 5 metres away.
I recall the citrus garden at Versailles - enclosed stone paved courtyard with I think a slope leading away, trees in pots, and of course a heated enclosure where the plants were moved every winter

Edit - I've just googled it, and not paving, but light coloured gravel - and a large pond (which I don't remember seeing) which should moderate temperatures due to the difference in thermal mass/ specific heat.
T

[jondear]

The best short term microclimate optimizer I know of is floating row cover. Either draped over the plants, or placed over short hoops. This year, I decided to use row cover over my melons to keep cucumber beetles at bay, as they decimated them last year.?

[mskrieger]

On Easter Island, which is quite cold compared to the typical climate enjoyed by Pacific Islanders, the people used to dig small sunken gardens with the walls lined with dark rocks that soaked up the sun's rays and then gave that energy off as heat well into the evening. This allowed them to grow heat-loving annual vegetables that otherwise wouldn't mature as well or as tastily (think of how difficult people with cool summer nights find growing eggplant or good tasting tomatoes, for example.) We can do the same with cold frames.

It's much harder to do this with trees and perennial crops, as just one stretch of really bad weather can ruin everything for a plant that took years to grow. In this case you need to look at the specific plant's weaknesses, and work around them.

EX. Fig trees fruit on young wood, which freezes and dessicates easily. So around here, where we are one or two zones colder than figs can thrive naturally, people keep the trees pretty small and wrap and/or mulch them for the winter. A similar strategy works for grapes in Canada and extremely cold parts of the US (and probably in Russia and Northern Asia too.)

EX. Trees that can ordinarily tolerate cold but deharden easily, losing fruit buds to winter thaws, might need the opposite strategy--plant them where they will stay cold and shaded all winter but get spring and summer sun.

EX. As others have remarked, citrus need abundant summer heat--so keeping them in a greenhouse might work if you live in a cool/short summer area.

If you haven't already read Coleman and Damrosch's books about gardening in Maine in the winter (The Four Season Harvest, The Winter Harvest Handbook) you might find them worthwhile.

[prairiegarden]

Jun 15, 2016 10:36:58 GMT -5 mskrieger said:

On Easter Island, which is quite cold compared to the typical climate enjoyed by Pacific Islanders, the people used to dig small sunken gardens with the walls lined with dark rocks that soaked up the sun's rays and then gave that energy off as heat well into the evening. This allowed them to grow heat-loving annual vegetables that otherwise wouldn't mature as well or as tastily (think of how difficult people with cool summer nights find growing eggplant or good tasting tomatoes, for example.) We can do the same with cold frames.

It's much harder to do this with trees and perennial crops, as just one stretch of really bad weather can ruin everything for a plant that took years to grow. In this case you need to look at the specific plant's weaknesses, and work around them.

EX. Fig trees fruit on young wood, which freezes and dessicates easily. So around here, where we are one or two zones colder than figs can thrive naturally, people keep the trees pretty small and wrap and/or mulch them for the winter. A similar strategy works for grapes in Canada and extremely cold parts of the US (and probably in Russia and Northern Asia too.)

EX. Trees that can ordinarily tolerate cold but deharden easily, losing fruit buds to winter thaws, might need the opposite strategy--plant them where they will stay cold and shaded all winter but get spring and summer sun.

EX. As others have remarked, citrus need abundant summer heat--so keeping them in a greenhouse might work if you live in a cool/short summer area.

If you haven't already read Coleman and Damrosch's books about gardening in Maine in the winter (The Four Season Harvest, The Winter Harvest Handbook) you might find them worthwhile.

That's interesting as I've seen pit or sunken gardens suggested for places like Arizona so as to get roots down into cooler soil and possibly conserve water. Since more heat wouldn't be wanted there they'd need to be thinking of sun reflection rather than absorption. The devil's in the details..

[mskrieger]

For sure. I've seen sunken gardens in the Middle East--makes it easier to irrigate them (you just flood in the water a couple times a week), and to shade them from the midday sun (big, strategically placed rocks). Interestingly, these Middle Eastern gardens were all in places with red sandstone type rocks. The Easter Island gardens used black basalt, as far as I know.

[philip]

I came across another good idea recently. I have a friend who told me that she started to mulch the soil around plants with sheep wool and then places lots of heavy rocks on top of that and then many smaller stones. That way she creates a rock garden that needs no weeding for many years.

You could also probably use carboard but that would desintegrate a lot faster.

So if you had a lemon tree in front of a South facing wall for example and then you mulch all the soil around the tree with sheep wool and make a rock garden that would create a very good microclimate.

[mskrieger]

I like that idea, philip, but citrus trees generally need a lot of nitrogen. Wouldn't the cardboard or wool tie that up for some time, preventing the tree from growing well? 

[philip]

Maybe it would. I admit that i don't know much about soil chemistry. But i picked the lemon tree as an example. The point is that my friend grows mediterranean herbs in rock gardens that need no weeding due to the sheep wool mulch. That in itself i find fantastic. I really despise the use of plastic, eventhough i use it myself.

So it's amazing to think how sheep wool as a mulch can create weed-free rock gardens and therefore favorable microclimates and how one could take all that a step further to grow cold-sensitive perrenials.....

[steev]

The nitrogen that matters is what's available in the soil; the wool, being on the surface, like my sawdust or bunny-bedding, has little impact on in-soil N. Wool is very good for long-term weed-block since it decays very slowly, compared to plant materials.

[prairiegarden]

I need to start making friends with sheep farmers.....