Help with sm. greenhouse for gardening

I bought a very small greenhouse a few years ago. It's put together with poles and fitted plastic that forms the greenhouse. I've tried using it in the past with terrible results. I live in Michigan and if I put it out 6 weeks before planting time, then everything dies because of the cold. If I wait, then by the time the plants are ready to put in the ground, planting time is long passed.

I try to plant my garden between May 15- 7 June, depending on the weather. I have been buying tomato plants, cucumber, zuchinni plants that are ready to put in the ground, but I'd really like to grow from seed.

Anyone in the northern climate use a greenhouse and can offer some tips?



[edit on 10-3-2009 by virraszto]

reply to post by virraszto


get a heat lamp and put it on the ground facing up ( on a safe platform mind you.) and have a small fan to circulate the heat. Mine made it through 25 degree temps here in northern California and is still going strong.
I am pretty sure you got colder but the same thing still applies it needs a heat & light source when the climate and sun are in a cold season.

I got a u2u from Dr. Love saying this post was deleted, yet it's still here. I asked my question on the other gardening thread in this forum.

reply to post by virraszto


See the other thread you just posted in.

Peace

set up your greenhouse and make sure you keep everything sterile. if you like growing your own veggies from seed you need to invest in a 20$ T-15 flourescent shop light and start your seeds inside in late december so they are big and healthy enough to handle the transplant. it is best to locate greenhouses in an area of southern exposure and have direct sunlight for around 6 hours a day. heat lamp will help but a propane heater with a thermostat will also produce co2 as a byproduct and plants love co2.

I have a lot of greenhouse experience, and live at 7,000 feet in CO (which is why I have greenhouse experience, lol).

The type of greenhouse you are using, is simply not suited for your environment.

The fitted plastic types offer zero insulation as far as temperature goes. What you need is a more traditional greenhouse, and a lot of thought has to go into how it's set up. Different glazing (the "glass") materials have different R values, your fitted plastic being as close to zero as it gets.

I'd recommend a triple wall polycarbonate, clear, with a minimum thickness of 10mm. this will give an R value of approximately 2 - 2.5.

Framing material is another factor. Aluminum is horrible in cold climates, unless it's an air-gap type of construction, where the frame exposed on the outside, makes zero contact with anything exposed to the inside.

Location location location... Make sure you're taking full advantage of your sun.

Flooring... What type of floor do you have? What type of foundation is this floor set upon. Here in Colorado, I even have to insulate my foundation from the earth that surrounds it. You want a floor that will provide you with a decent amount of passive solar heating. Something that will store the heat from the day, and give it off during the cold of the night.

Believe it or not, water substantially outperforms concrete, pave stones, etc. in this respect. Get yourself a 55 gal. drum, fill it with water, and just leave it in the corner, out of the way. You'll be amazed at the stabilizing affect it will have on your inside temps.

If you post a few more details about your greenhouse, as well as the orientation to the sun, maybe even a picture or two, I can probably help a bit more. My entire greenhouse is hydroponic, so I can also monitor and adjust the temperature of the water/nutrient solution that interacts with the plants roots. You'd be surprised how hardy vegetables can be when they have warm roots. Something to consider, as often making your greenhouse viable in the winter time, will turn it into an oven in the summer time.

A small electric heater will most likely do the job of keeping your green house above freezing.

Also seedlings need ventilation. A small fan is good for this. Open the door to the green house during the warmest time of the day and turn your fan on and also let fresh air in.

If you do not want or can't buy new a new fan and heater you may find by searching Goodwill, Salvation Army and Habitat for Humanity and other second hand stores.

There is a web site in most all states that is called Free cycle. You would be surprised at the things that people give away.

Good luck with your garden. I'm starting my seeds this weekend for my garden.

As someone who designs, builds, installs, home greenhouses and hydroponic vegetable gardens for a living, I beg you not to use an "upside down heat lamp", or propane heater in your greenhouse. Doing either one will ruin your garden as fast as the cold.

If you must utilize active heating, use electric only. Then you get to deal with the problems that go with electric heat, like single digit humidity levels. And please ensure that your garden has an extended period of complete darkness every night. If it doesn't get it's sleep, your garden's production capabilities can be significantly decreased, even eliminated all together. Want to see a tomato plant grow great all season long, but produce not a single tomato? Keep it under 24 hour light.

The net of the issue here, unfortunately, is that you're not using the "right tool for the job". Your fitted plastic greenhouse is simply not designed or intended for cold weather environments. It's great for keeping a light frost of the foliage, but that's about it.

[edit on 3/10/2009 by Unit541]

The greenhouse I bought is just a cheap style one that you can find at any garden store. It would be equivalent to covering a wood frame with cheap thin plastic. I think that Unit541 is right that it won't do the job.

Someday if I could afford it, maybe I'll invest in something better, but for now, I guess I'll have to settle buying my plants.

Thanks Unit 541 for the informative post.

reply to post by Unit541


I'm interested in what you think of this design for a south-facing parabolic-reflector walled growhouse:

[atsimg]http://files.abovetopsecret.com/images/member/1da2e7566aa4.jpg[/atsimg]

[atsimg]http://files.abovetopsecret.com/images/member/6150de83bbc1.jpg[/atsimg]

The principle behind it is that the suns rays pass through the glazing to the plants inside, and are also reflected by a painted white/mirrored mylar covered parabolic curved rear wall which focusses the light energy down to a thermal mass below where the figure is shown standing.

This acts to keep the interior environment, and particularly the soil, at a constant warm temperature year round enabling good root growth

I've no info on those images to cite any design references, but am curious to hear your professional opinion though.

[edit on 10-3-2009 by citizen smith]

reply to post by virraszto


I wouldn't give up so easily. Especially if you're only trying to get an early start. Decent fluorescent grow lights (NEVER use incandescent) can be had relatively cheaply ($50 - $100, depending on your specific requirements).

Simply start your seeds in your living room, or bedroom, or basement, or garage (on a reptile heating mat), and grow them into sturdy seedlings under your light. Sun comes up, lights go on. Sun goes down, they go off. Once you've had your last hard frost, move 'em into your garden, and enjoy!

Please let me know if I can help in anyway. I've also got parts and equipment for all types of indoor gardening, including lights, so let me know if there's anything I can do. Helping other people grow their own food is my life's ambition!

"or propane heater in your greenhouse. Doing either one will ruin your garden as fast as the cold."

could you elaborate on how a propane heater being used at night to keep your greenhouse from freezing will ruin a garden. co2 is required for photosynthesis, without co2 most plants cannot grow. the same goes for using a green light bulb with one of those china hat grow lamps, the green light spectrum will not mess with the flowering cycles of plants, and would also help prevent freezing. we have a homemade pvc greenhouse that thrives throughout the winter. we live in western washington and do just fine with tomatoes and strawberrys and herbs. it not like we're talking about maintaining a coliseum or some other aeroponic or fogponic system, it shouldn't be a huge problem to make a little greenhouse work. light, food, water, co2...you can throw in ph, air flow, and humidity as well but it is pretty basic. hydroponic or soil applications very, but are accomplished with the same basic principles, just depends on how hard you want to make it I guess.

Plants, like most humans, don't thrive as well as possible using any type of artificial heat in the winter.

A few years ago I used a coal/wood heater in my green house.

I don't build or design green houses for the public but I do grow healthy plants.

With the proper light, ventilation, heat, and humidity you can make seeds sprout just about anywhere. To make them flourish you do need air movement and sunlight. The sun is a free source of light so I don't use grow lights.

By the way the type of propane heat I was suggesting was the small type that is used in a tent when camping.

Yes, I am aware that it is not safe to have an unvented propane heater on in a tent all night and have ventilation when using it and turn it off when I'm ready to go to sleep. Just added that in case someone posting in this thread decided To tell me how unsafe it was.

You will get many different ideas about gardening just as people have many ideas about how to raise children.

I would suggest that you take the best from all the ideas and use the supplies you have to be successful with your green house.

reply to post by citizen smith


I've actually seen a few greenhouses that employ that very concept. They're particularly useful in very cold climates in remote locations, where artificial heating is simply not feasible. The ability to focus and concentrate the suns energy on a thermal mass will lower the affect on temperature that short days and week sun angles have.

It's kind of like starting a fire with a magnifying glass. The big variable here is the thermal mass itself. "Soil" is horrible for this purpose. It will disburse residual heat to adjacent soil at a much higher rate than the air above it.

A much more efficient employment of this concept would be to use a more traditional greenhouse, and one or two simple concave reflectors. A painted wall is simply not very effective at concentrating the suns energy. Think of a modern capacitor. Is it more effective to charge the capacitor by putting it in the proximity of a mild electromagnetic field, or connect a wire to it's terminal and 'pour' electricity directly into it.

Having an opaque, reflective north wall may raise the ambient temperature a bit, while the sun is out, and will certainly provide significant insulation against the northern cold, but I feel that in this day and age, there's simply better ways to maintain the inside environment. I'd also fear sunburn (on the plants that is) with this type of setup anywhere but the farthest northern latitudes.

A small solar hot water system uses the same concept, although much more efficiently. The solar panel heats the water, which is plumbed into open containers in the greenhouse. The volume of water in the open containers acts as your thermostat. As the weather warms as summer approaches, the amount of water in the system is gradually reduced. As the summer gets hotter, farther and farther from your gardens ideal comfort zone, the water is again increased, this time offering a cooling affect during the day by absorbing ambient heat from the greenhouse.

reply to post by Jnewell33


Plants do need CO2, for sure. Although just as humans get goofy in a pure oxygen environment, plants can also be exposed to "too much" CO2.

I install supplemental CO2 systems all the time, but burning propane to get CO2 is the absolute worst way to get it. First of all, a veggie garden will die without sufficient moisture in the air, and if you've got enough combustion going on to actually heat the greenhouse, you'd be doing well to have RH at 2 - 5%. To be effective, propane heaters have to be used in some sort of forced air system, as burning natural gas puts of fairly low amounts of ambient heat.

So not only are you drying the air with combustion, but you're then circulating this dry air throughout the greenhouse, effectively wicking moisture right out of the leaves of your garden.

It's simply not feasible to heat a greenhouse with a propane heater. Especially a propane tent heater. One of these guys would barely raise the temperature in a residential greenhouse a degree or two. If your greenhouse is small enough for it to effectively heat it, your greenhouse just became a food dehydrator.

Greenhouses need radiant heat. As long as it's radiant heat, you can use just about any method you like. I've seen a few greenhouses in year round production using only a couple of crock pots filled with water as the heat source. Heated cattle or horse troughs are also a very effective method of maintaining greenhouse temperatures, with the added bonus of being able to grow water plants right in them (for those that are aesthetically minded).

edit for spelling.

[edit on 3/10/2009 by Unit541]