Want a Greenhouse, But Best Place is Worst Place

s4ntos3(9)September 24, 2007

So I've been toying with the idea of building a greenhouse in my backyard, but location is a big problem. The best place to build the greenhouse, due to landscaping and the size of the yard, is a large pit located on the north side of my home. Let me explain:

The pit is an alcove that provides access to the garage from the backyard. It drops about 2 feet from the rest of the yard. The north and west side are open to the yard, but the west side is only 2-3 feet from the backyard fence which stands 6 feet high. The south and est side sides are bounded by the home itself which stands 10-15+ feet high. The house is a south facing home, so this pit is pretty much in the shade for most of the year. I would say that it only receives full sun maybe 2-3 months during the summer.

I would like to use the greenhouse for a small vegatable garden. As I see it, I have 3 major problems:

1) Light...North side of a building. The greenhouse is gaurunteed to be in the shade for most of the year.

2) Drainage...2 feet deep pit. I can't recall this area ever getting filled with water, but our monsoons can be fairly heavy at times I don't usually run outside to stare at the pit when its raining.

3) Heat....During the winter this area will likely take a while to heat-up.

My plan is to use a greenhouse kit (most likely aluminum frame) and then do the following to address the problems I mentioned above:

1) Light...Artificial lighting. I plan on using grow lights for any part year where the greenhouse is not receiving full sunlight for most of the day.

2) Drainage...install a sump in the area in case it does flood. In addition, the plants will be grown in containers 3 feet or so off the ground.

3) Install an electric heater to help warm the greenhouse in the winter.

Unfortunately, I don't have room inside my home or the garage to house an indoor garden and this area of the yard is begging to be utilized.




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buyorsell888(Zone 8 Portland OR)

Shading and cooling are the big greenhouse problems in Phoenix. Not heating and lighting. :) Not being in full sun is likely a blessing.

The greenhouse doesn't need direct sun for plants to get light. It reflects. I seem to remember our greenhouses being covered with whitewash and shade cloths even in winter when I was in the vocational horticulture program in high school and then college in Phoenix. The greenhouse at the nursery where I worked was in partial shade too but was covered. It was twenty years ago so my memory could be wrong but I think you need to worry much more about cooling. You are going to need a big swamp cooler and multiple fans and can probably get by with running a small electric heater out with an outdoor extension cord for those few freezing nights.

    Bookmark   September 24, 2007 at 1:16PM
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I have pretty hot temps here in southern New Mexico, but not as hot as Phoenix. Because of your cooling challenges, I wonder if it wouldn't be helpful to talk to other folks with greenhouses in your city. There's an Orchid Society of Arizona, and it looks like they have meetings in Phoenix. (You could even just email one of the officers, asking for basic greenhouse info.) I looked at their online forum, and found one post saying that all of their members do in fact use swamp coolers in their greenhouses.
Arizona Orchid Society website

We get monsoon rains here too, and I agree it's something to plan for. I'm adding screen panels to my new greenhouse as an aid to my cooling problems, but I'm reminding myself that summer monsoon rains will blow right in through the screens (unless I design a solution for that too.) I'm also waiting for the delivery of an exhaust fan with enough power to exchange the air twice a minute at the highest setting. A swamp cooler may be in my future, but I want to try some other (simpler) methods first.

I don't have the experience to comment on the low-light question...but I think there are probably lots of folks here who have had to locate greenhouses in less than perfect spots. Best of luck!
Sheri (Las Cruces)

    Bookmark   September 24, 2007 at 6:32PM
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greenhouser(Middle TN Zone 6)

Unless one is growing tropical shade and partial-shade plants there will be an excessive need for extra lighting. I don't believe several hours of sun a day is enough for most food crops.

    Bookmark   September 24, 2007 at 7:57PM
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Thanks for the replies folks. If I do use artificial lighting, will crop yields be negatively impacted. I suppose that question depends in part on the crop, but my understanding is that most florescents are an average substitute for natural sunlight at best.

Thank again,

    Bookmark   September 25, 2007 at 12:34AM
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This link says growing under fluorescents (instead of sun) will reduce yield and increase maturation time...but then again, yours would be a mixture of the two:
Growing Vegetables Under Fluorescent Lights

IÂve read HID (High Intensity Discharge) lights will provide better results than fluorescents (although they cost a lot more.) One link below also mentions using reflective materials like mylar to increase the light level (that might be another tactic you could use.)
Info about HID Lighting
Lighting Your Garden

This might be a good book if you decide to do further research into HID lights:
Gardening Indoors with HID Lights

    Bookmark   September 25, 2007 at 12:24PM
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buyorsell888(Zone 8 Portland OR)

High pressure sodium lights are the best to supplement natural light. Not cheap to buy or run. fluorescents can be used to start seedlings but not for fruiting/flowering.

Partial sun in Phoenix is like almost full sun in many areas.

Raised beds to have improved soil would yield just as many veggies as a greenhouse and be a lot cheaper. Even using whiskey barrels would work.

I miss gardening in Phoenix. I have a greenhouse so I can grow the plants I miss!

I'm going to have to use lights even in summer here. I had to take the shade cloth back off as everything was stretching for light.

    Bookmark   September 26, 2007 at 1:06PM
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My original plan was to build a couple raised beds. My research kept telling me to make sure I got full sun so then I started thinking greenhouse to essentially provide a weather barrier for the lighting. And now that I got the greenhouse idea stuck in my head, I'm really looking forward to it. In fact, I'm giving serious consideration to building the greenhouse from scratch since the location also houses an A/C unit which takes up 6 square feet or so.

But, it sounds like the best plan might be to build the raised beds that I was going to use inside the greenhouse first and see what kind of production I can maintain. Thanks for the input.


    Bookmark   September 26, 2007 at 3:19PM
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buyorsell888(Zone 8 Portland OR)

Research that says full sun likely wasn't written for Phoenix.

Truly, I cannot imagine anyone using artificial lighting in Phoenix unless they are growing dope in a spare bedroom. LOL ;)

    Bookmark   September 27, 2007 at 2:10PM
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