Hi all,

I am new to the forum, new to gardening and to greenhouses. So I have a lot of catching up to do. The greenhouse is 9 by 15 and iron with glass, I hope to grow vegetables in there.

So far from browsing I understand that in the greenhouse temperature can be up to 10 degrees higher than outside and heat loss is mostly at the bottom.

Is there an upper temperature that I should avoid? What is good to grow inside?
I live in the Netherlands and I think that compares to hardiness zone 7(a), but I am not sure. We do have wet and cold winters with some snow and freezing weather and summers can be wet and cool too, but temperatures can go up to 35 C in summer, which would be an exception. In general it is around 20 C in summer.

The garden I have is on a complex so it has plenty sun, nothing blocking the sun. I also have a good size part of the garden left, for outside planting.

I am open to any wisdom you can hand me to make my greenhouse/vegetable gardening a success.

thanks
Annelies

Since you state temperature in C and we in the US use F, I did not take the time to convert your highs with mine here in Mississippi (zone 8b). If the outside temperature here (measured in the shade) is 90 F, and we probably have 90-120 days when it reaches that temperature, the temperature in the greenhouse will be 100-110 unless it is well ventilated and has fans to move the air. Since my greenhouses have their vents and doors closed in the fall/winter months, on a sunny day, when the temperature outside is 45 F, it is common for the greenhouse temperature to be 70 F without artificial heat. You are correct that the floor will be cooler than the upper part of the greenhouse. All my heaters are near the floor and automatically come on when the temperature reaches 50 F. The floor may be 50 F, but the upper part of the greenhouse will be closer to 60-65 F.

I start several vegetable plants from seeds in February and continue through March. The outside temperature would average 45-50 F for highs and 30-35 F for lows. I start several varieties of tomato, onion, lettuce, and herbs and a single variety of asparagus. They will either be transplanted into large pots or a raised garden in April, when there is no danger of frost, or grown in ever-increasing sizes of pots to sell in May. I am a hobbiest grower. Ken

I often see better than a 15C difference on sunny days in my greenhouses unless I vent heavily. Anything above about 37C tends to be pretty hard on the plants in the humid, closed greenhouse environment, so my ventilation gets more aggressive in hotter weather.

Glass is a very poor insulator, with high loss rates in both radiant and contact heat. Iron frames also tend to leach away heat. I don't know that I would count on the ground being your biggest source of heat loss, though it will be a significant heat sink, retaining both heat and cold.

The floor will be a lot cooler, but your heat loss is through the roof. I have a heater in my greenhouse and keep it about 12ºC to 15ºC at night. During the day, if it is sunny, it will get above 30ºC, with an outside temperature of 5ºC. I have a couple of roof vents that I open to keep it cooler during the day. I don't run the heater during the day, unless it is cloudy and cold. I cover the greenhouse with blankets at night for temperatures colder that -10ºC. The blankets on the roof reduce the heatloss significantly.

I keep bigger plants on the floor and smaller seedlings higher. I also keep the temperature sensitive plants like coleus and such higher up too. It really helps if you have a fan mounted about 6 feet high. The house will stay much warmer at night with a high fan and a heater on the floor.

Joanne, I'm so impressed with your GH!!! And your plants!!! BEAUTIFUL!

Hi and welcome! I live in South Carolina, USA. My greenhouse is about two thirds the size of yours and in summer I open the vents and use a box fan on a bench at one end to keep the air inside moving and use a window screen on the front door to keep the squirrels out. It's really important to keep the air moving in both winter and summer. I also wash the panels of my greenhouse in the Fall and let the panels get dirty as it actually helps in filtering out some of the strong light we get here in the South. When I lived in Southern England and had a greenhouse I noticed in Summer that the angle of the sun was such that too much heat was never a problem as long as the roof vents were open.

My climate similar to a British climate. I use my greenhouse January through May to start seeds/plants/mostly annuals and vegetables. I also overwinter a few plants in there. In the summer, I leave all the doors and windows open, day and night, as it is way too hot in there to grow anything, and we don't get any rain July/Aug and most of September.

I heat the greenhouse with an electric heater that maintains a minimum temp of around 50.

Technicalities of variations in temps at the floor vs. the ceiling really matter very little in a small greenhouse, except for perhaps the most finicky of plants/seeds.

I love my greenhouse. It's paradise for me in there, and a peaceful sanctuary.

Joannabanana---your pics are fantastic. It looks like you organize your greenhouse similar to mine. I feel like the luckiest girl in the world to have one.

Stephanie, your green house is beautiful too. Love the entry area! I haven't had time to do anything "pretty" to mine yet as it is loaded with seedling! But after I get them out I really want to make mine pretty as well as functional.






South end door view

Cool pics! I like that idea of that in ground bed you have in the corner. It's fun to meet others on this forum who are as ambitious with their seed starting as I am. It's my favorite thing about gardening---starting all of those babies in my greenhouse. I'll take some pics of the inside of mine perhaps tomorrow and post. Similar set up. And of course, never enough space, right? I have a brick floor, which I like very much.

You're right, NEVER enough space. I have tens of flats of seedlings outside the GH as well and at least 20 over to the farm already.

I would love a brick floor, but this one's getting mulch when I get it emptied this summer. My son bought me a used GH at his house that he put a brick floor in the aisle, pea gravel under the shelving units and in ground area across the back. And even with two GHs, still NEVER enough room!

Would love to see pictures of your inside and seedlings!

Never enough space indeed .. Last fall I ended up having to buy another one just to hold the rest of the tropicals and its jammed pack as well .. I already need a 3rd greenhouse! I use pea gravel on the sides and pavers in the middle of my main greenhouse I also made mini plant decks to keep the plants off the ground which helps in air circulation and use 2ltr bottles painted black with water in them for passive solar heating - I put those under extra tropical plants to keep the soil temperature a bit higher.

I wish I had enough room to put a bed in mine for starting seeds! That is an awesome idea.

Great set-ups everyone. I like the pavers and may consider adding some to my GH. I started way too many tomatoes and have a space issue. One lady is taking 90 at the end the month, so that will help

A 3rd GH?

But seriously, I UNDERSTAND! Nice set up too!

I have the water cooler bottles filled but I need to paint them black. Maybe by fall. And someone, I think Joanne has a compost bin for heat in her greenhouse. I want to do that this fall too! I love the idea of brick or pavers but I'm fine with mulch too and since that's what I have on hand....

Joanne, I got to move my tomatoes outside with 80 temps for the next few days. And it looks like it's close to being save to leave them out here, fingers crossed. Just in time because the next wave of plants are going in. I'm taking down the two metro shelves in my DR!!!

Now, just to sort what I want to sell and what I need to get planted. I have planted two days straight but I've a long way to go. Hopefully it will be a lush garden this year!

Lol .. pretty much 1 person is responsible for me needing another greenhouse .. she lives in NC and I live in SC and we meet twice a year half way between each other and always have our cars loaded up with plants for each other. You know, it wouldn't be so bad if the plants didn't grow - but grow they do. And we just can't say no.

Here are some pix of the second one .. it was actually pretty cheap and I wrapped plastic around the frame before putting on the cover. Did really well this winter. Didn't lose anything.

That is so great! So, are you starting new plants all the time or buying then to keep exchanging? If all of yours keep growing you're in real trouble.

I do that with my daughter in MI. only we don't do half way, mom goes to her! I start her stuff from seeds and then we go nursery hopping up there. She has some really good and cheap places around her. So I go home with a load also. Only she gets mad a me if they don't live and won't give me any more! LOL! She's given me a gorgeous geum (smoke - geum triflorum) three times now and all three times it has died. And I love it and really want it. Finally she told me she had lots of babies and I can have more!
http://www.prairiemoon.com/see...

I confess, I actually do have a third gh, but it's a cheapy. I don't heat it and it doesn't hold any heat. but it's great to work in out of the wind. Was going to sell it when I got my new one but now DH doesn't want to. I over wintered some spider plants and dracena and gerbers in there with no heat and extreme temperature shifts. Other than storing stuff, it's not much good for anything.


Your second one looks like a good set up and out of the wind with the fence there. when you say you wrapped plastic around the frame, do you mean just around the framework or lined the entire house? Bubble wrap or what kind of plastic. I have a vision of you with a big roll of glad wrap!

I rarely buy plants - I'd venture to guess that at least 80% of my garden had been acquired through starting seeds and making trades that started with a rooted cutting of Solandra maxima for a Chocolate Cherry Canna about 15 years ago. Once I get both gh's decanted and everything sorted out, I'll put up a list of plants for trade on my website.

Here is a picture of the greenhouse getting the plastic put on - that's my helper Vanessa. The two of us went from kit in a box to sticking in plants in a little less than 4 hours. I'll be spending the summer thinking about how to make it a more secure and permanent structure .. the frame is really solid and sturdy.

My kind of acquiring. But I do buy plants occasionally. I prefer starting cuttings or seeds, like to watch them grow and the challenge! I'll share anything I have as long as it's not my last one.

Oh, it's plastic like I use for row cover! Duh. I just couldn't get that saran wrap picture outta my head!

At market the vendors tie filled (sand or water) milk jugs to the frames to hold their tents down. I wonder if they couldn't do double duty for you, heat and weight? We had a hoop house (homemade) before GH and DH would zig zag rope back and forth and secure it down that way. Not pretty but it worked.

Finally my promised pics of the interior of my greenhouse. It's a disaster right now, but these are 'real life' pics of a working greenhouse! This glass greenhouse was purchased on Costco.com and assembled by my husband. Our landscapers leveled the ground and built the brick floor. Our electrician did the electric work.


General pics of the interior. The wooden potting bench came with a Christmas tree we bid on and won at a charity auction---it was decorated in a garden theme, and a number of gardening items came with it.


Nifty shade cloth has hanging straps, and you can pull it to extend across the whole greenhouse. I use it often on sunny, warm days.


Interior water spigot.


Mounted heater, mainly used at night in Jan/Feb/March


I have 8 outlets in there.


A little bonus, although I never work out there at night anyway.

kosk0025,

Your GH is HUGE! Love the set up. I wish I had water in the GH. Great tip on the shade cloth