Outside RMH for orchard idea

I am a RMH newbie looking for some sage advice from the old hands.

I grew up around orchards that used "smudge pots" (pots of oil) on freezing nights to keep from losing citrus trees. The environmental aspects horrified me even as a kid, now of course even worse. But I still have a dream of using an outdoor heat source to keep out-of-zone trees alive on freezing nights in an environmentally friendly way.

Farms in the area where I live now might get ~10-30 freezing nights a year, and any colder than -6°C / 21F would be super-unusual. So the cold is not usually severe or prolonged and I've been thinking in the name of self-sufficiency it might be a worthwhile effort to rig up a system for frost-tender trees. I was thinking that some kind of outdoor RMH could do the trick, maybe in combination with some kind of tenting with thermal blankets/row covers.

A major goal would be getting a whole night's worth of heat out of one fire as spending your life getting up in the middle of the night to tend to freezing trees is a bummer.

Would like to hear people's ideas about the feasibility of the concept in general, finishing materials that might work outdoors, air flow and draw, insulation underneath yes/no/how, etc., etc. I'll just leave it there and let the experts speak.

Have you looked into Sepp Holzers method of growing citrus? Paul Wheaton has talked about it recently in one of his podcasts. I understand it has a solar reflector pond in front and a heat retaining berm behind. Might be right up your alley.

Another thought is a large high tunnel that can utilized during the cold nights and then left open the rest of the year. A RMH inside would do a lot more than one outside. I don't know about your location but where I live wind chill would be a huge factor in heat loss.

I'm not sure one RMH outside would be enough. You might need a series of them in a ring around the trees. I think having some data from an out door RMH and the temperature differences at various distances throughout a typical night would be great information.

One question I try to ask myself before starting a project is "do the gains justify the means?" Will the profit of selling the fruit or the benefit of having it grown on your property be worth the amount of work that goes into keeping the plants alive?

Best of luck on your adventure.

Rex Reeves wrote:Have you looked into Sepp Holzers method of growing citrus? Paul Wheaton has talked about it recently in one of his podcasts. I understand it has a solar reflector pond in front and a heat retaining berm behind. Might be right up your alley.

Another thought is a large high tunnel that can utilized during the cold nights and then left open the rest of the year. A RMH inside would do a lot more than one outside. I don't know about your location but where I live wind chill would be a huge factor in heat loss.

I'm not sure one RMH outside would be enough. You might need a series of them in a ring around the trees. I think having some data from an out door RMH and the temperature differences at various distances throughout a typical night would be great information.

One question I try to ask myself before starting a project is "do the gains justify the means?" Will the profit of selling the fruit or the benefit of having it grown on your property be worth the amount of work that goes into keeping the plants alive?

Best of luck on your adventure.

Hey Rex, thanks for chiming in! I really appreciate your input.

Yes, I'm a big fan of Sepp's. In the design I'm working on, there is a substantial slope going down to the west (WxSW), so a reflecting pond to the south is not going to work. Citrus trees would be in a northish-southish line up against a WxSW-facing gabion wall, and behind the wall may be a rocket forge among other things, so between the west and slightly south orientation and what's behind I'm hoping the rocks will provide some warmth.

The high tunnel structure is a great idea. I could leave a hoop structure set up (maybe a half-hoop given the gabion wall on the uphill side) and cover it as needed. I've wanted some kind of tenting strategy but if there is some way to kind of accordion-fold the high-tunnel cover that might be great. Does anyone know of a video showing some sort of an idea for something like a retractable high tunnel cover? Or any other kind of retractable cover outdoors for trees?

You're right that it would be nice to have data about temperatures at various distances from an outside RMH. The effect of the "smudge pots" with oil in them used in citrus orchards of my youth must have been substantial, even though they were dotted around pretty sparsely, because people actually used them and it can't be cheap to light a pot of oil on fire. If memory serves me correctly, maybe there was one smudge pot every 5 or so trees in a row, maybe every 10, I don't remember too well as I was a kid. I think an RMH bench running by each tree would have to work way better.

I'm thinking of a long series of RMH benches covering about 40 meters (130' or so). This would go between a line of the most sensitive trees like, say, lemons, which would be against the gabion wall, and the second line of less sensitive trees (satsumas or whatever). And have some system rigged up to cover the whole deal when freezing temps threaten.

There are big greenhouses already in this design, and I don't want the place to become a plastic jungle. That's just my hesitancy to having the trees under permanent cover, there will be other more tropical trees under permanent cover in the greenhouses. I basically need to provide potentially +7°C (12-13°F) temperature support maybe 30 nights a year.

The "justification" for all of this is basically self-sufficiency. For one, resiliency, so if supply chains deteriorate at some point people still have what they need locally, and second, because there are some things that are marginal or impossible to grow locally, that realistically no one is going to give up: lemons, bananas, mangoes, pineapples... Maybe people would cut back, but I for one am not going to say I'll never have a pineapple again because I don't live in the tropics. So rather than setting myself up to import these things over tens of thousands of kilometers for the rest of my life and exploit the whole third world export agriculture chain, it seems reasonable to develop a really eco-smart way to grow what people are actually going to consume, locally. Which is what this is all about.

Don't want to create an ethical firestorm about this. Part of the reason I'm inclined to go for it is that my area does not have a severe climate, but there are a few freezing nights every year. Providing some support over those few freezing nights, you really open up the window of what it's possible to grow locally.

I went and read about how the old pots worked and what has been replacing them.
I want to see if the smoke was considered a bug or a feature.
I was concerned that it was contributing to the heat transfer/ distribution.
Seeing as the smudge pots are being replaced with "clean burning" propane, it seems that the smoke isn't important.

You could build individual rockets with bells for long term radiant heat, or you could build a single rocket powered "boiler", heat up a mass of water and run water lines wherever.

If you are already gonna have a greenhouse, you could have a water tank as a thermal mass, solar and/or rocket heated and run loops to  barrels where you want radiant heat.
That being said, individual solar tank collectors could serve individual trees or zones.

Dave de Basque wrote:

Hey Rex, thanks for chiming in! I really appreciate your input.

Yes, I'm a big fan of Sepp's. In the design I'm working on, there is a substantial slope going down to the west (WxSW), so a reflecting pond to the south is not going to work. Citrus trees would be in a northish-southish line up against a WxSW-facing gabion wall, and behind the wall may be a rocket forge among other things, so between the west and slightly south orientation and what's behind I'm hoping the rocks will provide some warmth.

The high tunnel structure is a great idea. I could leave a hoop structure set up (maybe a half-hoop given the gabion wall on the uphill side) and cover it as needed. I've wanted some kind of tenting strategy but if there is some way to kind of accordion-fold the high-tunnel cover that might be great. Does anyone know of a video showing some sort of an idea for something like a retractable high tunnel cover? Or any other kind of retractable cover outdoors for trees?

You're right that it would be nice to have data about temperatures at various distances from an outside RMH. The effect of the "smudge pots" with oil in them used in citrus orchards of my youth must have been substantial, even though they were dotted around pretty sparsely, because people actually used them and it can't be cheap to light a pot of oil on fire. If memory serves me correctly, maybe there was one smudge pot every 5 or so trees in a row, maybe every 10, I don't remember too well as I was a kid. I think an RMH bench running by each tree would have to work way better.

I'm thinking of a long series of RMH benches covering about 40 meters (130' or so). This would go between a line of the most sensitive trees like, say, lemons, which would be against the gabion wall, and the second line of less sensitive trees (satsumas or whatever). And have some system rigged up to cover the whole deal when freezing temps threaten.

There are big greenhouses already in this design, and I don't want the place to become a plastic jungle. That's just my hesitancy to having the trees under permanent cover, there will be other more tropical trees under permanent cover in the greenhouses. I basically need to provide potentially +7°C (12-13°F) temperature support maybe 30 nights a year.

The "justification" for all of this is basically self-sufficiency. For one, resiliency, so if supply chains deteriorate at some point people still have what they need locally, and second, because there are some things that are marginal or impossible to grow locally, that realistically no one is going to give up: lemons, bananas, mangoes, pineapples... Maybe people would cut back, but I for one am not going to say I'll never have a pineapple again because I don't live in the tropics. So rather than setting myself up to import these things over tens of thousands of kilometers for the rest of my life and exploit the whole third world export agriculture chain, it seems reasonable to develop a really eco-smart way to grow what people are actually going to consume, locally. Which is what this is all about.

Don't want to create an ethical firestorm about this. Part of the reason I'm inclined to go for it is that my area does not have a severe climate, but there are a few freezing nights every year. Providing some support over those few freezing nights, you really open up the window of what it's possible to grow locally.

Always happy to add my two cents Dave!

The gabion wall is an excellent application of heat retention and wind blockage. Adding a half tunnel for the cold season is also a great idea. here is a video on roll up sides on a tunnel. I did something similar against my quonset a couple times to get my tomatoes an early start. https://www.youtube.com/watch?v=2GyYAnsyuLc  However, a high tunnel large enough to cover two rows of trees would be a massive investment and structure. Any covering will need to be replaced eventually, thin coverings like greenhouse poly every few years and sturdier ones like glass only when damaged by severe weather or animals/lawnmowers.

Having a straight line of trees will make everything easier, but will also allow wind to pass straight through taking heat with it. What I learned about heat application in the outdoors, when there is a wall of some sort, is to sandwich the thing to be heated between the heat source and wall. ie: a person in a survival situation should build a fire away from a stone wall and sit in the middle. The wall blocks the wind and reflects heat back at the person. That sounds like what you described doing with the RMH, tree and gabion. This is a tried and true technique and I am sure it will do what you want.

My other thought is to place the RMH against the gabion. Depending on how cold it gets and how often, you may be able to get the results you want without taking up more ground space than you need. The RMH will lose less heat to the air and will shed more heat into the gabion for a larger thermal mass. Essentially turning several separate RMH into one large one. I think I would prefer this setup if I was using the tunnel.

Those are excellent reasons to tackle this project. If your goal is to have something that is sustainable in a SHTF situation I suggest not having the tunnel because finding replacement coverings would be difficult and the tunnel advertises that there is something of value inside. A row of trees is just a row of trees from most peoples perspectives but a greenhouse shouts food, or other stuff. I think the tunnel would be useful and beneficial for a long time and if a SHTF thing happens I'm sure you would be able to adapt the setup as needed.
I don't see any ethical reasons not to do any of this.

Any thoughts to the guild plants under the trees? If you are successfully growing warmer climate trees you could grow warmer climate companions.

William Bronson wrote: I went and read about how the old pots worked and what has been replacing them.
I want to see if the smoke was considered a bug or a feature.
I was concerned that it was contributing to the heat transfer/ distribution.
Seeing as the smudge pots are being replaced with "clean burning" propane, it seems that the smoke isn't important.

You could build individual rockets with bells for long term radiant heat, or you could build a single rocket powered "boiler", heat up a mass of water and run water lines wherever.

If you are already gonna have a greenhouse, you could have a water tank as a thermal mass, solar and/or rocket heated and run loops to  barrels where you want radiant heat.
That being said, individual solar tank collectors could serve individual trees or zones.

I have no knowledge about the old smudge pots but I was wondering about the smoke too. It would be full of particulates and moisture.

I know a few things about trees and water lines though. Heating with waterlines in the floor is one of the most convenient methods on a large scale. Heat rises and conducts so it is an even heat and reduces stratification. I played with the idea of heating a greenhouse with water lines buried about two feet down. For annuals this would be a great idea. For perennials, especially trees, not so much. The roots can grow around the lines and either pinch them off or puncture them. Tree roots are extremely destructive, which is why paper beats rock.

Water tanks near the trees would be an excellent option for the outdoors. They can be moved as needed and heated via solar gains or small rocket burners of various sorts.  

A lot of people, the glorious Sepp included, spray water to prevent frosts on sensitive plants. A large RMH heated tank that sprays automatically at a certain temp might be an option too.

This was something i had wanted to do as well , we have a frost season and it is usually over a night ,so i was hoping to mitigate the effects on some of the fruit trees without a long term use or enviroment damage, the smudge smoke does seem to have been purposely been part of it, the belief being it created a smog blanket , not read anything  to prove or disprove  this yet .Seen these being used ,very popular in germany as patio/garden heaters so i thought if it was upscaled a bit or a bigger pellet hopper it might burn long enough , i could easy make up the steel part of it ---plenty of free plans up on the net and open source , but the schott glass tube ---about 130.00 euro with postage.  Or an experiment with the log style rocket stove ---in a suitable firepit

Where do I buy one

It looks like there are some sellers on Etsy who make those rocket fire torches. As well as one in the EU.