6 Months In the Greenhouse

April 16th, 2009 by david laferney Leave a reply »
My greenhouse is cram packed in April.

My little greenhouse is cram packed in April.

I built my 50 dollar greenhouse about 6 months ago and I thought some of you might be interested in what I’ve done with it and how it’s performed so far.  I have not used any artificial heat in my greenhouse at all – so it does get cold in there – but the climate in the greenhouse is much more temperate than it is outside. I’ve found that even in the worst weather we have here in zone 6 cold hardy things like spinach and lettuce keep on growing all winter long – although at a slower rate than if it were warmer.

I haven’t installed any kind of automated ventilation system so far – I just watch the weather forecast and if it’s supposed to be a warm sunny day I open one of the doors in the morning, and close it in the evening.  This has worked pretty well, but I must admit that there have been times that it was already in the 90s before I got around to ventilating.  I’ve really been surprised that all of my lettuce hasn’t bolted because of it, but so far (April 15) none of it has.  I must admit that during periods of moderate weather the greenhouse is almost like having livestock in that it requires a little bit of attention every day.  Also, it should be obvious that you have to water in the greenhouse even if it rains outside – however your plants are protected from the trauma of snow, hail, and torrential rain.

In Middle Tennessee (zone 6b) you can’t grow tropical plants or produce fruits like tomatoes through the winter in an unheated greenhouse like this.  There are growers in our area which do grow “hothouse” tomatoes so I know that it’s possible to do it, but I don’t see that as being practical for me.  If you live in a warmer zone however it might be for you – check around to see what other people are doing in their greenhouses.

What I’ve Used My Greenhouse For So Far

Fresh salads all winter – Because I built the greenhouse so late in the fall I didn’t really get the salad greens cranking until after Christmas, but once they did get rolling I’ve had a steady stream of salad greens ever since.  I grew many varieties of lettuce, Teton (F1) spinach, and arugula (planted in mid February – arugula planted outside on the same day failed completely while that in the greenhouse literally grew like weeds) and they have all done great – despite single digit temperatures on multiple occasions these crops continued to grow all winter long, and I’m still picking greens from seeds that were planted in November.  Being able to eat home grown produce all winter long was one of my main goals when I built the greenhouse, and it looks to be easily doable.

Extra early broccoli – Broccoli is one of our favorite vegetables, so as soon as sets became available at the local farmers co-op I planted some in the greenhouse.  Well, I am getting broccoli extra early, but the plants are also bolting to flower extra quick because of the extra heat units that they are getting.  Next year I’m going to plant the spring broccoli under a simple poly tunnel row cover to get a fast start and then remove the cover when florets start to form.  Broccoli as well as the other members of the cabbage family are not freeze tolerant so wont grow throughout the winter in my greenhouse, but should produce extra late in the fall – I’ll see in a few months.

Extra early tomatoes – I’m still working on this.  I planted out celebrity and early girl tomato plants amongst the greens about March 15 – a month before our traditional last frost date – and they have grown very nicely so far.  I don’t know if I’ll actually get early tomatoes out of this experiment, but I have high hopes that I will.  I’ll let you know in a couple of months. Update – I am getting early tomatoes from the early girl plants that I planted out in the greenhouse, but they are only about a week ahead of others that weren’t in the green house.  However, I removed the cover from the greenhouse in April and a few days later we had a cold front go through that might have been a factor – I think I should have waited a bit longer, but the weather had been really nice.  I’ll try again next year.

Enjoy gardening on a cold winter day – This is one of the few things that you can do with a greenhouse that you can’t do in a cold frame.  Even when the sun isn’t shining the complete shelter from the wind makes a remarkable difference in your comfort level, but when the sun is shining it’s like a trip to the Keys.  I took this picture on a sunny day in January when it was 5 degrees outside –

5 degrees outside - 50 degrees inside.

5 degrees outside - 50 degrees inside.

Notice the ice on the inside of the greenhouse plastic – also notice the 70% relative humidity – on a 5 degree day the humidity outside is like zero.  It’s amazing how good 50 degrees can feel when the sun is shining on you and you’re out of the wind.

Garden when it’s raining or snowing – even if all you want to do is pick some lettuce or plant a few seeds – you are always in out of the weather.

Grow out bedding plants – We grew about 6 flats of pansies from seed last fall, but because we got that bright idea a bit too late they weren’t ready to set out until late winter.  The greenhouse was the perfect environment to grow out the tiny plants to a good size to set out.  By the time we had spring bedding plants that we needed to grow out we were out of room in the greenhouse.  Next year I’m going to try to plan for this a bit better.

Things I haven’t done yet

Extra late tomatoes – With some luck we should be able to pick garden fresh tomatoes until almost Thanksgiving.

New potatoes for Thanksgiving – Potatoes are a cool season crop, and I’ve read that you can have fresh new potatoes for Thanksgiving or even Christmas if you plan right.

Propagation – This year we had great success starting seeds indoors under lights by using a home made bottom heat propogating table.  If you have electric service to your greenhouse (I don’t) you could start your seeds in the greenhouse using bottom heat in a cold frame, and you wouldn’t have to have artificial lights.

Forced flowers – This isn’t something that I’m into, but you should be able to force tulips and other spring bulbs into bloom much earlier than normal by bringing them into the greenhouse.

Force strawberries – This is something that I am into.  Next fall when I transplant strawberry daughter plants I might put a few of them into containers so that I can try this.

Kiln dry lumber – in the heat of the summer, cover the floor to minimize humidity, stack stickered lumber, ventilate to remove humidity while elevating temperatures as much as possible.  If you have electric service in your green house you could also seal it up and run a dehumidifier – almost all of the water will be coming from your lumber.  I doubt if I ever do this, but it sounds like a good idea if you can’t use the greenhouse in the heat of the summer anyway.

I don’t know of anything that I would want to grow in my greenhouse in the heat of the summer (cacti?) and I intend to take the plastic off of the frame once the weather is reliably warm so that I can use the space for regular crops during the summer, and also to make the plastic last longer.


It’s turned out to be a good choice to grow in raised beds instead of in containers – containers would require much more frequent watering, and would be much more likely to freeze than the soil in my raised beds.  However, next fall I’m going to add a thick weed free layer of enriched  soil to the top of the greenhouse beds to help suppress weeds.  Weeds haven’t been a huge issue in my greenhouse because it’s relatively small, and fortunately most of them have been chickweed – which is quite tasty.


Fungus gnats – These little buggers hatched out in early winter for a few weeks every time the weather would warm up for a few days.

Fungus gnats look like tiny mosquitos and hatch out in the soil to feed on organic matter.

Fungus gnats look like tiny mosquitos and hatch out in the soil to feed on organic matter.

Supposedly they damage your tender young plants by feeding on the roots in the larval stage, but I couldn’t really see any evidence of this.  They mostly just beat their selves to death on the inside of the plastic.

Moles – Our area has been experiencing a biblical type plague of mole for the last few years.  Some areas of my yard are solid with mole tunnels, and they have done some damage in the garden as well.  So far I haven’t found any way to control them that I’m comfortable with.  I’ve  seen plenty of evidence of moles inside of the greenhouse, but so far very little damage to what I’m growing.

That’s it – so far I haven’t really had any problems at all with insects, disease, or vermin in my greenhouse.  I’m probably jinxing it by saying so.

Now that I have a little bit of experience under my belt using my small greenhouse I see that this is a tool that I enjoy using and that can extend the productivity of my garden throughout the entire year.  I wish I had built it sooner.


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