Cactus greenhouses in colder zones (6, 5, 4, etc)

Do-it-yourself projects such as greenhouse or shadehouse builds and related topics.
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Aloinopsis
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Cactus greenhouses in colder zones (6, 5, 4, etc)

Post by Aloinopsis »

How realistic is it to keep/get/build a cactus greenhouse year-round in colder climates?

Most of the successful ones I see are in the West or South (of the USA), but for those of us in the Mid-Atlantic, Mid-West, and Northeast, is it really feasible to keep a 12' x 10' greenhouse heated to a minimum of 45º? Just as an example, of course.

But I have 272 plants (mostly Mammillarias, Gymnocalyciums, and others that benefit from a chilly, dry, winter) indoors in a giant unheated room, but when I move house later this year, I'm going to have to figure something else out for next winter.

If anybody has done this in a colder zone and been successful (or not) I'd love to hear about it. Specifically, insulation and heating (if applicable) are things I'm not particularly well-versed in.

Everything is still in the "planning" stage for me right now, and I've read through this forum a couple of times but the information "blends together" so if there's already a particular thread on these forums I would also love to be directed to it.

Thank you so much!
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cactushobbyman
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Re: Cactus greenhouses in colder zones (6, 5, 4, etc)

Post by cactushobbyman »

On the greenhouse side, I would think wind, snow and ice would be the biggest concerns. I would do an internet search for your area and see what is out there. A well built greenhouse using polycarbonate triple wall and around 16mm would work, but no less than 8mm. I don't heat and my greenhouse on some nights the lows are 30 degrees. I stop watering in November and depending on the weather, I will start watering in late February. The cactus you listed will do fine if dry down to 30 degrees.
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Aloinopsis
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Re: Cactus greenhouses in colder zones (6, 5, 4, etc)

Post by Aloinopsis »

Thank you. What USDA Zone are you in? Just curious. I didn't realize California had Zones 5 and 4 at all.

My area reaches the teens at night frequently in January, but there is mostly rain or ice.
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7george
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Re: Cactus greenhouses in colder zones (6, 5, 4, etc)

Post by 7george »

I have seen a detached greenhouse in Calgary that is considered in zone 3 (or 4) but its heating expenses would been high I guess. Not sure how much, it would depend on the material, size, electricity price and winter length.

Image

Most people I know in Canada have sun rooms (or a conservatory) attached to the house that is much easier to manage in winter.
Last edited by 7george on Tue Jan 08, 2019 7:43 pm, edited 1 time in total.
If your cacti mess in your job just forget about the job.
°C = (°F - 32)/1.8
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Aloinopsis
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Re: Cactus greenhouses in colder zones (6, 5, 4, etc)

Post by Aloinopsis »

Thank you. That is really helpful.

Do you mean "attached?" Maybe I misunderstand something (very possible!), but if it's detached it would effectively be a greenhouse, right?

If it is attached, does it normally face south? I'm trying to form a picture in my head.
DaveW
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Re: Cactus greenhouses in colder zones (6, 5, 4, etc)

Post by DaveW »

Not sure about your snow and wind, but we have been growing in glass heated greenhouses for centuries in the UK and they stand up to some quite strong winds, as do the commercial ones.

Generally speaking these days ours are all glass and the normal pane size is 2ft x 2ft in the aluminium ones for those using ordinary window glass rather than toughened. The problem with polycarbonate sheets is often being much wider than this they need a centre fixing or they can bend and "pop out" in high winds.

Those who heat them usually line them with bubble wrap plastic to conserve heat, but if not UV stabilised it does not last long before deteriorating, though UV stabilised only lasts about 6 years anyway. I usually leave mine up all the time in my 18ft x 12ft greenhouse as it's too much trouble to take up and down each year as some do.

Unless you want to grow tropical cacti 40F minimum is warm enough for most cacti since every few degrees hotter than the outside temperature really bumps up the cost of heating because the bigger the differential between the greenhouse temperature and the outside air the quicker the heat is lost through the glass or polycarbonate. I have seen one calculation that every extra degree of unneeded heating adds 3% to the heating bill, how true that is I do not know.

"overheating a greenhouse by a couple of degrees increases the rate at which heat is lost through the glass/polycarb, so from the money you spend on over-heating the greenhouse more of the heat is lost"

Lining a greenhouse with bubble wrap:-

https://www.gardenersworld.com/how-to/g ... ubblewrap/
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7george
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Re: Cactus greenhouses in colder zones (6, 5, 4, etc)

Post by 7george »

Aloinopsis wrote: Tue Jan 08, 2019 2:05 pm Thank you. That is really helpful.

Do you mean "attached?" Maybe I misunderstand something (very possible!), but if it's detached it would effectively be a greenhouse, right?

If it is attached, does it normally face south? I'm trying to form a picture in my head.
My mistake: I mean attached of course. Looking south most often, can be west or east sometimes. You can open or close doors to rest of the house if you want some colder or warmer air inside.
If your cacti mess in your job just forget about the job.
°C = (°F - 32)/1.8
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Aloinopsis
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Re: Cactus greenhouses in colder zones (6, 5, 4, etc)

Post by Aloinopsis »

Thank you everybody for such helpful replies!

As I understand it, the UK is warmer than most of the US/Canada. Is that correct? I could be wrong about that because I have a learning disability and I don't always "translate" temperatures correctly. But from my understanding, the coldest parts of the UK are the highlands of Scotland, which have equivalent temperatures to Zone 5/6 in the US so it's still warmer than most of our northern zones.

Maybe I've misunderstood that (totally possible, lol).

I'm thinking that when all is said and done, it shouldn't take much to keep something heated to 40F because we only have a few weeks each year below that. For example, for the next few nights it's going to be 19F (-7 Celcius).
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Re: Cactus greenhouses in colder zones (6, 5, 4, etc)

Post by Pereskiopsisdotcom »

This is a project I have been seriously putting together for a while now in zone 5 Canada. I've been for years using a mix of a sunroom as 7george mentioned and a grow room complete with thousands of watts of lights. As mentioned, the sunroom is attached to the house so it shares in all of the electrical and heating. It's on the south side with glass but because it is simply a room attached to the house it is limited in what can be accomplished for a small business (that's me) and of course, it also serves a function for people to enjoy during the colder months.

I have been told numerous wild stories on the differences of cost with heating an unattached greenhouse in our area. They're actually quite rare to find. The few around me that cater to annuals and vegetables every year are essentially turned off until early spring because of that cost.

One option that I'm looking at now as I prepare to build a large greenhouse is to actually bring the plants to a storage location when the colder temperatures arrive and just rely on emergency heating in the late spring and early fall. Ideally, the cacti could be in the greenhouse from April through October. An unheated, dark, dry basement with some air circulation would be ideal and likely be great for flowering (especially for the species you like to grow). Obviously, it's a lot of work doing all of that moving but if it's only a couple of times a year and the two locations are near it wouldn't be so bad.

What have you discovered?
http://pereskiopsis.com

Interests include: Rhipsalis, Turbinicarpus, Gymnocalycium, and Lophophora.
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Aloinopsis
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Re: Cactus greenhouses in colder zones (6, 5, 4, etc)

Post by Aloinopsis »

I have actually had the EXACT same experiences and observations--that freestanding greenhouses basically don't happen in my area, or, when they do they're uninhabited for winter (i.e, they grow annuals, fruits, vegetables, etc only from early spring to late fall).

I do wonder about the attached sun rooms. At some point, wouldn't the size outweigh the practicality? I mean, most south-facing walls on a house have other things there (windows, heating units, driveways, etc) so even if you had a solid brick wall most homes would probably not be extremely conducive to that.

If I buy a home in the next few years I'm going to look for as much unobstructed southern or eastern wall space as I can find, though.

I've even thought about having a "room" inside a greenhouse where the most sensitive (to cold) plants could be kept, so basically a heated central "room" with the rest unheated. I don't know how practical that is (or isn't), though.

I've also seen wildly-varying estimates like you have. It makes sense, since structures are built, maintained, and heated differently. But the huge variation is what puts me off the most, because of the uncertainty.
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panaMark
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Re: Cactus greenhouses in colder zones (6, 5, 4, etc)

Post by panaMark »

I live in Idaho where it gets really cold sometimes. We always get at least a couple spells of -20 F each winter. (Coldest I have seen is -45 F) I do exactly what Pereskiopsisdotcom does, and bring them into dormancy storage once the attached greenhouse gets too cold. I keep a "hi/lo" thermometer in the greenhouse so I can monitor the temp trend and when it gets obvious that night-time temps have made it dangerous to keep the plants in the greenhouse, then I move them to my winter storage (a slightly heated shop building). Then in Spring when the temps are doing okay at night in the greenhouse, I start bringing them out of dormancy for the move to the greenhouse again. It actually is an enjoyable if time consuming task. Some of the most cold-hardy cacti stay in the greenhouse quite late into winter. I also fill the greenhouse with sealed buckets of water in the cold seasons to act as daytime heat sinks for the night cold.
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Aloinopsis
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Re: Cactus greenhouses in colder zones (6, 5, 4, etc)

Post by Aloinopsis »

Does your all's winter storage have much light? I'm imagining a cool, unlit, area. Is that correct?

I've overwintered cacti like this in past years (cool, dark, dry, garage or something) but that was when I had "only" 100 or so pots. Now I've got...significantly more. lol

Also, what kind of high/low thermometer do you use, if you don't mind me asking? I'm interesting in getting one.
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Re: Cactus greenhouses in colder zones (6, 5, 4, etc)

Post by DaveW »

"As I understand it, the UK is warmer than most of the US/Canada. Is that correct?"

UK is probably warmer in winter than many parts of US or Canada, but far more humid. We therefore get freeze, thaw, freeze, thaw, conditions over winter which the plants do not like. Many cold countries where the plants come from freeze or cover them with snow at the start of winter and do not thaw again until the start of the growing season. Therefore plants outside do not get wet and then frozen repeatedly throughout the winter, neither are those in their greenhouses subject to cold humid conditions, but usually dry cold.

The Americans and Canadians when they came over in the War claimed Britain does not really get cold compared to their countries. Then all walked about shivering since humidity makes both cold and heat feel far more intense than the thermometer indicates.
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Aloinopsis
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Re: Cactus greenhouses in colder zones (6, 5, 4, etc)

Post by Aloinopsis »

Gotcha. I live in a temperate rainforest (in the Appalachian Mountains) where it's wet and below freezing all winter. The worst of both worlds! lol
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panaMark
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Re: Cactus greenhouses in colder zones (6, 5, 4, etc)

Post by panaMark »

Aloinopsis wrote: Thu Jan 10, 2019 2:16 pm Does your all's winter storage have much light? I'm imagining a cool, unlit, area. Is that correct?

I've overwintered cacti like this in past years (cool, dark, dry, garage or something) but that was when I had "only" 100 or so pots. Now I've got...significantly more. lol

Also, what kind of high/low thermometer do you use, if you don't mind me asking? I'm interesting in getting one.
I have a couple different thermometers, but the best value/bargain I have found is this one: https://www.amazon.com/gp/product/B01AL ... UTF8&psc=1

My dormant area just has a bit of light from a north window and any random lights I have on in the shop while I am briefly working there. The most important IMO is stable temp of about 45 F or so and dry.
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