Greenhouses

[General Schvantzkoph]

I'm thinking about getting a greenhouse this year to extend my season (I live in Massachusetts). Last fall someone on this group suggested I try a popup greenhouse because they are very cheap (under $150, some as low as $50), rather then make any kind of major investment. Does any one have any experience with them? There also seems to be a class of greenhouses that are a step up, around $600-$700. The cheap ones are basically plastic tents, the mid priced ones are aluminum and polycarbonate. I'd like your opinions on both types. In my heart of hearts I've always wanted a proper glass Victorian greenhouse, but that's real money so I want to see if a greenhouse is helpful to me before I make that kind of investment.

[Suzanne D.]

I bought a $110 plastic greenhouse from Walmart. It was easy to assemble. The workmanship was a little shoddy, but nothing drastic--just a zipper off-kilter, some crooked seams, that sort of thing.

There were two problems I saw, and these might not be problems for you:

1. It didn't stay warm at night. I'd see seedlings popping up during the day (when it was VERY hot inside the greenhouse), then they'd die overnight. If you are going to put some nighttime heating in it, then this probably wouldn't be an issue for you.
2. The wind completely took it away. We staked it down all around AND put concrete cinderblocks around the perimeter of the greenhouse, but on one windy night the entire thing was pulled up from its stakes and blown into a tree, where it twisted and broke. The plastic was ripped, and the metal bars were bent and sheared clean off at some places. (A few of the stakes were still in the ground; the wind had separated the poles at the joints and lifted them away!) If you do not have a lot of wind where you live, this shouldn't be a problem.

I really like the idea of these inexpensive greenhouses, but for me it was a waste of money.

--S.

[General Schvantzkoph]

Thanks for your feedback. Both of those things are issues, I wondered how something that was basically a tent could stand up to any kind of wind, apparently they can't.

[Bill who putters]

Maybe nestled up to a south facing wall with east and west protected with a few cider blocks. As I understand it auto venting device is really of import or the heat which varies a lot due to no solar mass fries or freezes your plants. I's add gallons of water maybe half your space to try to moderate the temperature swings. Small maybe beautiful but one has to work harder on your design.

[The Cook]

I bought a 12.5' x 8' greenhouse from Costco about 5 years ago. I love it, but even here in NC you can't do much to extend the season with heat at night.

It was somewhat cheaper when I bought it. It was on sale and we were up at midnight to get online and order it. The price includes shipping.

The interior gets down to whatever the outside temps are at night. As soon as the sun comes up it starts getting hot. With the door closed and a nice bright day it will be 105° inside. We ran water and electric when we poured the slab. This one comes with lights, fans, shelves and other stuff. I have discovered that it is cheaper to germinate seeds in the house and then move them out to greenhouse than to try to keep the GH warm enough at night for germination.

As I mentioned in another thread, I am getting a late start this year. Besides we had snow the beginning of this week. Tomorrow it is supposed 61°.

Think carefully and specifically what you hope to accomplish with a greenhouse and how much you would like to have in it. About April one of my 8' shelves is packed with trays in various stages before setting out. If I got very ambitious I could clear the shelf on the other side. The cost of heat can be a real bear. I did not heat the greenhouse this winter and it was so cold that our electric bill was double what it was last year. I will be putting some trays out there in a few more days so I will have room to start some more things.

Ask more questions as you think more about what you want.

[General Schvantzkoph]

That one is starting to be real money, the problem with even thinking about spending several thousand is that the next step is to start thinking about spending 5 to 10 times that much and getting a really nice one. This year I want to keep it down to a few hundred dollars, maybe as much as $650, something like this

of the other reasons that I'm thinking about this is to protect some tomato plants from blight. Last year I nearly lost everything to early blight. I read somewhere that protecting plants from wind and rain reduces the transmission of blight, can someone comment on this?

[David Hare-Scott]

My experience is limited to a small cheap portable one that would probably be called a cold frame more than a greenhouse but it has all the problems that you will face with a bigger version.

- Too hot when the sun shines on it and high humidity encourages fungi, I have to open up flaps to allow it to cool on warm days.

- Blows away in strong wind, I move it to shelter and/or tie it down.

- Loses heat quickly at night, I move it under shelter.

- Limited lifetime, even "UV stabilised" plastic will only last a few years.

David

[Pavel314]

We're in Maryland, a bit north of Baltimore. We bought a $700, 10' x

12' greenhouse kit from Harbor Freight a few years ago and put it up on the south side of the house. It heated well with a 220 volt heater but wouldn't stand up to the wind. The first windstorm sent about a third of the panels all over the property. I tried to add extra clips and adhesive but the next windstorm still took off a few panels. The structure was too flexible, allowing the doors to open and the wind to get in. I tried adding cross-members inside to strenghten it but it was pretty much gone by that point.

The next year, I built a wood-framed greenhouse against the south side of the house. I recycled most of the panels and windows from the original greenhouse for the walls of the new one and put heavy-duty double-wall polycarbonate panels on the roof. Everything held against the winds for two years and against over four feet of snow on the roof this winter.

Paul

[The Cook]

I am not sure that a greenhouse is going to keep late blight away. The spores travel through the air and you cannot keep a greenhouse closed during the summer. Today I checked the temperature in the greenhouse and it was 134°. The outdoor temperature is about 60°. Check this site on late blight.

[Jeff Thies]

I like that idea.

You may wish to look at home made hoop greenhouses. Easiest way is to drive rebar into the ground, and pop the hoops on the exposed rebar. You will need to recover every few years, but the material is cheap.

One example:

My general advice, curves are strong and resist wind. If you can prop this against a south facing wall you will cut your heating needs. Greenhouses lose heat at night, and lots of it. Without added heat, inside temperature will be the outside temp by morning if not long before.

As I understand it auto venting device is

Water is one BTU per pound water degree F. Heat loss for single layer is ~ 1 BTU/hr per square foot times the temperature difference. It adds up to a lot of water as Bill has said. Try Drums. Other materials store heat, but not as well as water.

Double or triple wall polycarbonate will cut the heat loss by almost a half to two thirds.

I'll retrofit my solar cabana with mylar storms this fall. Clear mylar degrades in UV so it needs a UV outer barrier.

I've been using vinyl shower curtain liners. They are very clear and hold up well, so far.

Jeff

Small maybe beautiful

[Billy]

I'd investigate composting manure for heating. Not very esthetic, but practical.

and reduce light by 20% - 30%, respectivly. Six mil polyvinyl will reduce light by 5 - 15%. In low light situations, this could be important. I was planing on a hoop house, but decided that I couldn't afford the light loss in my particular situation.

[Jeff Thies]

Perhaps perhaps run pex through the remotely located compost pile and pump the heat into the greenhouse when needed. Lot's of options.

It's always a tradeoff. You could have removable insulation and put it in at night. But that can be a hassle. I've done some removable with reflective bubble wrap such as this:

I also have this on the north wall and it reflects light in rather than letting it escapes. It can also be pulled over the top, instead of inside.

I've got some folding multilayer 1 mil mylar "storms" that has very low light loss, but it has it's issues.

My benefit here is that while I have very little sun during the summer, falling leaves changes all that. I may have to become a winter gardener...

At any rate, there is a lot to consider. And I'm afraid more that the casual greenhouse user would like to consider!

As you have said, anyone can grow in ideal conditions, it takes a gardener to grow in what is available!

Jeff

[Billy]

Before I started to garden, I found the smell of manure very offensive. Now when I smell manure, I think of gardening.

[Bill who putters]

Happy Fathers Day ! Sometimes wonder why we did it in hindsight glad I did. Sometimes I think what is next. Ups and downs and all around as I listen to

Lir 18:10 Wim Mertens Close Cover New Age AAC audio file 100 1

8/2/09 6:03 PM 1986