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Fruit Trenches: Cultivating Subtropical Plants in Freezing Temperatures (lowtechmagazine.com)
264 points by Luc on April 17, 2020 | hide | past | favorite | 102 comments

"Training small citrus plants was key to extending their cultivation across all regions of the Black Sea coast, where until then it had been impossible. This was achieved by pruning and guiding citrus plants into a creeping form, which reduced their height to a mere 25 cm."

People complain about cubicle farms, but there's so much we can do to train workers to be productive in them, if we start them young enough.

Finally an industrial application of bonsaikittens.

We should notice than a 25cm height Citrus is not necessarily a 25cm wide Citrus. Could extend for a few meters. In the end is the opposite to a cubicle. Creeping plants are space hogs.

> pruning

Do IT workers really need legs?

Of course not, if you can automate feeding. Sadly the current armless interfaces are not efficient enough, otherwise there is a big potential there as well. But the bonsai approach if applied young enough, should give efficiency boosts, too.

Y'all need to watch Sorry To Bother You. No spoilers.

Super awesome! I imagine that most of the time, you don't even need to dig giant trenches, though. Sepp Holzer grows citrus in the freezing alps above ground. Their average temp is 5C.


Sepp Holzer's farm is amazing. I think however it's unlikely that he's truly able to grow citrus fruit at scale even using all of his near magical techniques. Where he is able to grow citrus fruit is taking advantage of very small micro climates with ponds buffering temperatures and acting to reflect evening sun along with perfect orientation etc.

Permaculture in general sadly does not produce at scale at all and scaling up is very labour intensive.

The average car in the US has a 120 horsepower engine, less if it's a compact, more if it's a truck or SUV.

Think about that for a second -- your garage is housing the equivalent of 120 horses. How much "labor" is that?

Now, we don't really notice that when everything is working well and the gasoline keeps flowing. There are calculations that figure a gallon of oil has something like two weeks of 8-hour/day manual labor embedded in it, energy-wise (using the cute term "energy slaves"). Synthentic fertilizer is basically spending a crap-ton of energy to fix nitrogen -- google "haber bosch energy".

Especially with the covid supply chain disruptions going on now, though, I've been rethinking what "scale" means or if it's even the right metric to be going for. Permaculture has been really interesting to me last few weeks because it doesn't try to go for "scale" per se (though there are claims that properly done it's more productive per acre), but rather it tries to cycle as many energy flows as possible.

So if your yardstick is "how many bushels of corn per acre can I grow?" then yeah, permaculture doesn't 'scale'. But if your yardstick is "how do I get the most output while minimizing energy inputs" and accept that outputs aren't necessarily a monocrop but can be complementary outputs (corn + legumes + animals + fertilizer), then it starts to get really interesting.

I'm a developer not a farmer, but the systems-level thinking I've seen in the permaculture community is extremely fascinating. There's 'labor' embedded everywhere, the question is are you counting it.

Not sure if you've come come across it but Gabe Brown has done some interesting stuff in farm scale low input farming.


That said, I think there is a lot of interesting stuff in permaculture design. But in a lot of cases it is a bit of a pyramid scheme / agile consultancy feel going on.

"But in a lot of cases it is a bit of a pyramid scheme / agile consultancy feel going on."

Definitely, Sepp Holzer is sadly a prominent example of this as well. There was a case of a new project, where a naive women, a true believer of permaculture, invested all her money in a permaculture school project under the guidance of Holzer, where all the ordinary farmers could learn how much more efficient permaculture is. And it failed spectacular and ended in court. [german wikipedia for more, english version is very small]

"Think about that for a second -- your garage is housing the equivalent of 120 horses. How much "labor" is that?"

Not it is not. A horse needs food, also if it is idle. A car does not.

And labour does not equal energy. The advancement of humanity did happen, because we found other energy sources and apply them, so machines can do the hard labour.

(now it is a struggle to adjust that system, but I believe globally the sun is excessively shining to provide all the energy we need)

"I'm a developer not a farmer, but the systems-level thinking I've seen in the permaculture community is extremely fascinating"

And to this I agree very much, but I would still rather bet on more traditional ways of feeding the world.

...except that you can go to a store where you can simply BUY for CHEAP far far more and more diverse foods than you could ever dream of growing.

No one who does this thinks it's efficient. It's just a fun hobby.

"No one who does this thinks it's efficient"

Erm ... clearly you have not met true believers of the movement ..

You need to look at the work of Mark Shepard. His work is all about farm scale permaculture.

He has a book Restoration Agriculture you can find on Amazon, etc.

I will, but I think I read quite some books about it and visited many permaculture farms and tried to apply technics in my own garden quite some time ago. And my conclusion is, there is way too much wishful thinking involved. For example I have never seen a permaculture farm that was actually self sufficient. Either they had other sources of income, or they had paid tours.

Permaculture is nice and I would like to see more of it adopted, but I don't see at all, how we could feed the current world population with it. With general ecologocal farming, yes.

Sepp <3

I grow a few things in a (relatively small) suburban garden in London. My experience so far with fruit normally associated with warmer climates:

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

Figs - grow well outside, fast, but not much fruit yet

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

Olives - grow very well outside, don't produce much fruit

Stauntonia - grow very well outside, no fruit so far

Hardy kiwi - grows well outside, produces some fruit

Normal kiwi - grow very slowly, no fruit, sensitive to frost

I would like to try pomegranates, I've seen some people grow them in London

The best croppers in my garden by far are non-tropical fruit - cherry and apple trees.

I think polytunnels (maybe with some kind of light transmitting insulation) and geothermal heating would be the way to go these days in northern climates if trying to grow cold sensitive fruit in larger amounts.

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.


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.

There was a similar article shared here a few months ago on Fruit Walls:


The fruit walls article a perennial favorite on HN.[0] (Pun intended.)

[0] https://hn.algolia.com/?q=fruit+walls

The soviet's probably would have liked this man's geothermal greenhouse which is a modern version of their trenches: https://www.youtube.com/watch?v=IZghkt5m1uY

Also, I'm wondering if the citrus grown in Russia ended up ripening in fall rather than in winter or whether they had to harvest the fruit in the middle of the winter. Also, I'm not sure how citrus would work being dug up every winter. Did these trees ripen in the spring? This is all fascinating and something I'd love to try in the US. I'd bet the premium on locally grown foods isn't enough to sustain a northern citrus farm, but it could be a good hobby.

This retire engineer in Nebraska has nice setup.


I wonder if these kinds of designs can handle smaller scales. I'd love to have such a greenhouse on my 0.3 acre lot in Wisconsin.

Edit: I found this guy's store page[0]. This is what they say about size: "Greenhouse in the Snow kits are priced by the lineal foot and are available in 6' increments beginning at 30'. The greenhouses are 17' wide. Most kits we sell are 78' to 102' long. Greenhouses less than 60' long are less cost effective than bigger greenhouses."

I imagine smaller greenhouses like this are still possible though.


Bear in mind that the ratio of the exterior surface to the volume of the controlled space gets worse and worse as you make it smaller. And that this ratio is what helps make it cost effective not just in material costs but in operating costs, since heat transfer is across that surface...

Where I grew up (41.3 deg N, on the Atlantic coast) I was always amazed by our neighbor, who would bury his ~15 foot tall fig tree every year to protect it from freezing. For some reason in my child mind it seemed to defy the laws of nature, though of course it was quite the opposite!

I couldn't visualize how this works so had to look it up https://www.instructables.com/id/Bury-a-Fig-Tree/

When I lived in Toronto, my next door neighbour Luigi did that with a fig tree he had brought with him from his native Sicily some decades ago. Every year it bore a couple dozen figs for him. The whole family was a living stereotype in pretty much every way, but his gardening technique definitely bore fruit.

Where I live in Eastern Europe (44°26′7″), we have acclimatized fig trees. And we have temperatures as low as -20C or even -25C (-4 and -13 Fahrenheit).

My parents who still live in the same house do have a small fig tree they don't bury, and my mother's parents a hundred miles south had a larger one in their backyard. I don't know if burying fig trees in that climate is necessary to be honest, maybe it was just a practice my neighbor brought with him (he was Italian as well).

How did he exhume it in the Spring?

The whole thing?

Yes, he would tie it down and create a kind of berm along its length.

Wow, this is amazing. The trenches are super cool, but there’s a wealth of info in the article, especially around how they arrived at creeping varieties, and how they cold-hardened lemons by painstakingly moving each successive generation’s seeds further and further north. Really interesting piece.

Very interesting reliance on epigenetics to get cold adapted varieties

I’ve often thought about the fact that most food into places like Barrow, Alaska is flown in, and wondered whether it would be practical to set up local infrastructure like this to grow food locally (with “practical” meaning “the CapEx of doing so would be repaid in logistical OpEx saved over a small number of years.”)

Forget about Point Barrow. I live in Upstate NY, one of the best Apple growing regions in the world. I’m eating an Apple grown in Chile while local orchards collapse.

Food has more to do with capital and commerce than anything else. The inefficiencies of consolidated global scale distribution require squeezing every penny on the production side.

It's not a requirement, it's a choice, and one with catastrophic downside risk.

Refusing protectionist trade policy became popular among the people who make these decisions, a trend which accelerated after the collapse of the Soviet Union. We're in the middle of a crisis which brought to stark light the lack of resilience created by this relentless focus on efficiency and productivity at any cost.

But this is policy, not immutable law. Markets do predictable things in the absence of trade protection, subsidy, and state investment, true; but they do predictable things in the presence of them also.

I’m not talking trade policy. It makes sense to get summer crops from South America in winter/spring! It ridiculous to get months old apples from there. The US regulatory and monetary system facilitates big players.

Today you have buyer cartels purchasing in bulk and fixing prices. They demand quantities and pricing that shut the market to most players.

I can’t buy lettuce in NY at retail because the supply chain from Arizona and California is fubar. Farmers in NY will be harvesting lettuce from high tunnels soon, but they don’t have access to markets and can’t scale.

The apple is not months old, but more likely a year old. They are kept in cold storage for extended periods of time.

The truth is that it makes horrible sense to ship crops to the US from anywhere outside of the US.

US agriculture policy is broken fundamentally. It is corn, soy, wheat. It is what is used as the feed stock for industrial food production. Basically, all the pseudo-food that lines your grocery store shelves. In the US, your tax dollars are used to subsidize the production of this "food" so that it is artificially cheap.

food security in times of disaster or emergency are other good reasons for investing in local food supply. Also, diversification of the economy. But ya, it needs to make some economic sense too.

We grow a lot of food in hothouses in Canada...

I would love to see the math of geothermal greenhouses powered by renewables versus the carbon footprint of air freight of food. As renewables drive down the cost of electricity, the economics continually shift towards local production versus import.

Outside of Alberta, most of Canada's electrical generation is very low carbon (nuclear and hydro) per electricitymap.org.

ya, but I think a lot of commercial greenhouses are heated by natural gas because of lower cost. A quick google found some really interesting stuff regarding alternative (geothermal, biomass) heating specifically designed for greenhouses: https://www.greenhousecanada.com/topic/structures-equipment/...

Current state, yes! But something we need to get away from (unless methane from bioreactors or landfills is used, in which case burning it is the best form of disposal).

Check out Iceland.


Slowly developing insulated indoor aquacultures, led lighting, robotic harvesting, perfect climate control, gas mixture, mineral and nutrients.

With near future robotics we'll see near zero carbon footprint production with near zero human work load for a fairly wide range of healthy foods.

This is very helpful, thank you for sharing!

They only account for 10% of the national population though.

I feel like with the advance of renewable energy sources and the lowering prices on things like solar panels, it might become quite plausible for places like Barrow to start growing their food with these methods, utilising zero fossil fuels (or close to zero.) I've seen videos of people with pretty sprawling underground "bunkers" set up for growing fruits and vegetables. They require tons of energy, of course, but if done on a governmental scale, I'm sure it can be pulled off. Both to provide more varied food options and to achieve self-sustenance as well as give an option for a worst case scenario where deliveries are impossible.

The government investigated that back during WWII. Unfortunately, the north slope is one of the foggiest, darkest places on earth. Additionally, the soil is thin and permafrost runs nearly right up to the surface. The local environment provides literally nothing to work with, so it was considered uneconomical.

Might work in other places though.

[video] Nebraska retired mailman uses low cost geothermal to grow citrus in -20F snowy weather -- https://www.youtube.com/watch?v=ZD_3_gsgsnk

The University of Minnesota has done a bit of research and put out some guidance on constructing deep winter greenhouses: https://extension.umn.edu/growing-systems/deep-winter-greenh...

They use a similar method in that thermal mass is used to store energy, but instead of trapping the heat with soil/straw for a season the daily heat is stored in masonry, stone, or water. On sunny winter days it can be -20°F outside while the greenhouse is 80°F, though a string of dark days can mean that supplemental heating is needed.

Some of these techniques are still common to produce hardy plants or increase yields with low land use. "Creeping" is also called low-stress training, and the extreme form is sometimes colloquially called "screen of green." SoG is so-called because you essentially put a net at a fixed height and force the plants leaves to all be at that exact height, attempting to maximize photosynthesis efficiency. (Really hot peppers varieties take some babying to thrive. These techniques are also popular in the marijuana community.)

It frosted only one or two days this winter in Odessa. So maybe in a few years, you will be able to grow mandarins above ground without protection.

Fruit Trenches are just an attempt at cheap walls. There is no geothermal going on here.

I'm not sure if it would work out cheaper. Certainly not for a business. But even for a hobbyist possibly not. I'm not sure it's even interesting as a display garden.

The bio-hacking (breeding) of plants is cool though.

An alternative is greenhouses. These folks have been growing tropical plants at 7200 feet in the Rocky mountains for years using inflatable greenhouses: https://crmpi.org/

The most hardy citrus is the ornamental Flying Dragon Citrus, which produces fruit, but the fruit is poor tasting. But can be grown in zone 6 Niagara Falls



The most tropical fruit that can be grown in cold climates in North America is the Paw Paw. (Survives -30 degrees)

"It belongs to the genus Asimina in the same plant family (the Annonaceae) as the custard-apple, cherimoya, sweetsop, ylang-ylang and soursop."

Flying dragon or Poncirus is a must if you want to grow Citrus in cold places. Is the only decicuous Citrus.

The fruits are non culinary, but is an excelent rootstock

In any case the "lemon" of cold places is Chaenomeles (and not all are able to bear fruit).

I oddly really want to do this, but I live in California so that would be quite pointless and most likely detrimental.

The Forestiere Underground Gardens in Frenso are over 100 years old. The trees grow in wells connected by shallow tunnels. It does look more like a Tatooine underground house than a garden, but still neat. It's open for tours in normal times:


Unless you want to grow plants that fare better in colder climates. Just cover them over in the middle of summer and make sure they have some sort of cool air flow through the trenches.

Reminds me a bit of the citrus gardens in Limone sul Garda.


I wonder if hackernews mods keep tabs on people carpet downvoting?

They do, and are usually pretty responsive to questions like this if you send them email at hn@ycombinator.com. I don't know if that's what's happening here, though.

For example, despite having a copy of one of Holzer's books next to my bed, I downvoted your "Sepp [heart]" comment. It's just not the right comment for HN: no context, and emoticons are really frowned on. If instead you'd written a few sentences explaining why you admire him, so that people who don't know who he is could understand, you'd probably have gotten a bunch of upvotes.

I'm sorry if it feels like people are attacking you. It's really not, instead it's really about trying to keep the site as good as it currently is. Almost all comment heavy sites of this age have declined to be unusable by now, but because of the different moderation approach, HN manages to (at least occasionally) still have quality discussion.

Climate-controlled cultivation will likely become a necessity for food production as climate change intensifies. Spain, South Africa, many Middle Eastern and other countries are already heavily reliant on greenhouses.

Also given that megadroughts, floods, and hurricanes are likely to be the new normal, sufficient capacities of solar-powered desalination will be important to sustain food production levels. My main immediate concern with climate change is that greater numbers of and more intense storms will destroy infrastructure and food production, leading to wars and/or pan migration.

Case in point: Parts of Spain look like a winter-resort on Google maps [0], but that's actually greenhouses.

[0] https://www.google.com/maps/@36.8292745,-2.7821357,115749m/d...

> Climate-controlled cultivation will likely become a necessity for food production as climate change intensifies

This is interesting, as massive greenhouse are seen in fiction as the only way to grow crop in hostile environments: Mars, the Moon, Space.

Who knew we would be making our own planet a hostile environment.

Problem is that greenhouses are the most laborious. Can’t drive a tractor through to plant and pick everything.

Actually its the other way around! Automation in the controlled environment of a greenhouse is much simpler to implement than out on a field. Ok, there are certain crops that still haven't been cracked in terms of automating the picking mostly due to fragility/spoilage of the items being picked, but other than that, you have a regulated climate/humidity/temp (you can pause "rain" , etc in sync with the tasks you want to automate), you have a flat surface for your machines, or vertical rigging to hang machines off of, etc.

Sure, but one guy with a tractor in a field has a lot of advantages over that.

Incredibly laborious. Pretty much everything has to be done by hand -- watering, fertilizing, etc. Totally worth it for specialized plants, or in certain climates, but you can't scale them to feed 6-going-on-7 billion people.

There are in fact about 7.8 billion of us. I believe we will have to change from this <1% of the population growing all the food.

Growing part of your own food is a good idea. We should all plant some potatoes this year – a not so laborious way of producing nutritious food.

Kind of Maoist and inefficient to have all your specially trained valuable first world labour do manual work, badly.

As a specially trained valuable first world labourer -- at least, my employer seems to think I'm worth a salary -- I find growing my own potatoes (and a few other things) a welcome break from my desk and screen.

I'm sure my garden is nowhere near as efficient as a real farmer could make it, but that's hardly the point. And a few rows of potatoes (even with my inefficient management), are a much more productive use of the land than a typical suburban lawn.

Do it if you enjoy it, but that isn't the point GP was making or responding to. (I also maintain a small garden, FWIW.)

In fact, it is in part the point I want to make. It is a giving pursuit, in more ways than one.

In my comment, GP is pjc50; not you. You literally said that everyone should plant potatoes, which I, and pjc50, disagree with. As I said before, do it if you enjoy it; it's not a great use of everyone's time.

Wait until you find our how little of the world's population builds and maintains the telecommunications, liquid fuel, and pharmaceutical ecosystems that we also reply on.


David Ricardo

Instead of a tractor, wouldn't robotics work? [1]

The scale would be much smaller, and the cost higher of course.

[1] https://www.postscapes.com/smart-greenhouse-robotics-materia...

The technic is pretty awesome, but in the video with tomato harvesting ... the robot is about a 100 times slower than a human at picking tomatos. So while there is potential for it, it does not seem ready yet. At least not for the real economy, where manual labour is still quite cheap.

Some of the industrial scale "greenhouses" I see are PVC frames with sheet plastic. Lift them right off come harvest.

Thanks for the heads up. Have you got the printed books version? If so, are they good?

If the temps are below 0f, it seems like none of this is preventing your free from dropping below freezing. Maybe it’s really more about the varieties they cultivated.

With modern crisper I bet you could Make some amazing frui trees.

Join together with some fellow biohackers and make a fun transgenic plant. It's not that expensive or difficult, if you choose the plant well. Then you're a proud God of GMO with your intellectual spawn multiplying to (probably not) conquer the earth...

But some plants are very tricky and costly.

I remember making my first transgenetic GMO in an afternoon back in the day.

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