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The Europeans also used 'fruit walls'. I'm thinking of setting up one in Portland. Basically a brick wall that you espalier a fruit tree to. You redirect your chimney floo or hot water pipes through the wall to keep it warmer than the surroundings in the winter. I'm hoping to be able to grow frost-sensitive hardy citrus.

https://www.lowtechmagazine.com/2015/12/fruit-walls-urban-fa...

The problem is that neither your chimney nor hot water pipes are continually piping heat. So the transient effect of the warm/cold cycles would likely make frostbite even worse.

...and leaving those heat sources on continually... well... that's very energy inefficient, to say the least.

Idea behind the brick is to add thermal mass -- it stays hot once it gets hot in the same way a freight train stays in motion once it gets going.

This is often done on north-facing walls in greenhouses. In winter when the sun is low, the thermal mass gets a lot of light and absorbs it as heat. Then at night it releases it to balance out nighttime lows. In summer when the sun is high up, because it's a wall there's less surface area that absorbs the radiation, so it's self-regulating to a degree.

Same idea is even used for seasonal thermal storage. Look up "earth batteries" on youtube, usually it's permaculture folks. Basically, put air circulation pipes a couple feet below a greenhouse. In the summer, you flush your (too hot) hot air through it, the ground absorbs the heat, and you cool off your greenhouse. In the winter, the same process absorbs some of the heat out of the ground. Some numbers I've heard is a greenhouse can stay at 50 degrees when it's -20 outside. Basically same idea as a geothermal heat pump, but much simpler because all you need is a blower fan and some pvc.

> all you need is a blower fan and some pvc

And a lot of land area.

That last part tends to be the problem.

The brick works as a thermal battery - if it's cold, you're heating your house, and the intermittent exhaust is keeping the brick warm. If you're not heating, well it's not cold so the brick temperature doesn't matter much.

Increasing thermal inertia in our housing is a great idea. It saves energy.

But: we need to build low energy housing to manage climate change. That means there is very little waste energy available. Last house we built was 230m2, family of 5, had a total energy consumption, including everything from heating to water to home electricity, sitting at 8000kWh/y. That's in southern Sweden (N58deg).

There is no relevant amount of waste energy available.

This is the kind of housing we'll need to meet future energy targets.

You can do a lot with an apartment balcony, too. Even though it's space-limited, the warmth of the building will help.

Though not inappropriate for the climate, when I lived in Ohio, I grew tomatoes, corn, and pumpkins in containers on my balcony. The pumpkin vines grew into the adjacent tree, and in the fall, there were small orange pumpkins hanging from the tree limbs, like fruit.

In Texas, I grew all kinds of citrus trees in containers on my balcony, as well as watermelons. The trick with watermelons is to hang the fruit inside panty hose so they don't get damaged. It made them wonderfully round.

Again, not a climatic challenge, since they say, "You can plant a broomstick and grow brooms in Houston."

> In Texas, I grew all kinds of citrus trees in containers on my balcony

The Hanging Gardens were given their name because of the trees growing above the ground ("hanging").

What was considered a wonder of the world is now something you can just do for fun.

> Citrus (lemon, lime and kafir lime) - Any frost is damaging, can only grow in pots and bring in during winter. Grows slowly and doesn't produce much fruit

Lime and kafir lime are very tender. If lemons do not work, I would suggest you to choose hardy rootstocks (Poncirus can stand -40C for a short time) and try Yuzu instead. They are seedy, spiny (as lemons or limes), and less interesting as fruit but more hardy. Tangerine is also a relatively hardy citrus.

Olives and Pomegranates, forget about it. Will grow but bearing fruit is a different thing.

Stauntonia looks promising. Can you tell us more about your experience with it?

Have you tried Artic kiwi?

London figs will bear better in pots, probably

Yes, I have arctic kiwi growing. It's very nice. Small sweet/sour fruit, I find them tasty. It's grown commercially in France now too, I've seen the fruit being sold a couple of times at Lidl late summer.

Stauntonia - it's an evergreen vine, with fleshy leaves, originally from Myanmar/Korea/Japan. In Japan I think they eat both young shoots and the sausage shaped fruit. It hasn't born fruit yet in 3 years - I think I might need another one for cross-pollination - but grows like crazy and has lots of very fragrant jasmine type flowers in the summer.

Tangerines are a good idea, will try!

> Grapes - grow very well outside, lots of tasty fruit, sensitive to mildew

When things open up again, you might consider visiting the are of Tenterden just to the south of you, which due partially to a warming climate, is now growing wine grapes for French winemakers (it used to grow primarily hops), as some grape growing areas of France have apparently gotten too warm.

I am jealous of your garden

All you need is a bit of outside space, and time. Takes a few years for fruit trees to grow

with regards to the olives, are you using water or brine to treat them?

neither - the two trees I have don’t produce more than a handful of fruit, so they are mainly ornamental. I don’t think the growing season is long enough for the olives to grow to a reasonable size

Is a different problem. Olives need very specific temperature conditions to flower well. Not too warm, but not too cold, either.