Growing plants in the greenhouse

Have you ever wanted a greenhouse? Most obsessive gardeners do, and who could blame them? Growing plants in a greenhouse is one of those exquisite pleasures Victorian gardeners understood. A greenhouse or sunroom full of plants gets a gardener through the cold, dark days of winter.

The greenhouse and cold frames on a cool morning. Notice the condensation on the windows. Everything is nice and warm.
The greenhouse and cold frames on a cool morning. Notice the condensation on the windows. Everything inside is nice and warm.

This is the third winter for our greenhouse, and we’ve figured out a few things after the first two years of growing. Here are my greenhouse musings from last year when it was eternal summer all winter long. After reading these, you may be green with envy, but may I give you some advice before you order that freedom greenhouse kit like I did?

Inside the greenhouse, the scent is heavenly because the string of pearls plant blooms most of winter.
Inside the greenhouse, the scent is heavenly because the string of pearls plant blooms most of winter. Soon, I’ll start sweet pea seeds, and have lily of the valley pips blooming too.

First, if you order your kit to be shipped to your house, you’ll need to be there with a forklift and someone to put it together. My husband and son spent two weekends building the greenhouse. Some of the process is shown below.

Also, note that you need level ground for the vents to open and close. Since we live on a hill, we had to level the space first. That took some work too.

Greenhouses require a good and reliable heating system. As for ours, it’s all automatic up to a point. We have a small electric heater that we use for backup in case the propane runs out, and just before last week’s ice storm, the propane heater did quit working. After much troubleshooting, speculation and testing, we figured out the propane regulator was busted, probably because it got turned upside down, and water got into it. At first, we thought we were out of propane, but we checked and that wasn’t it. Then, we thought it was the heater so we bought another for approximately $250.00, but we were able to return it after replacing the regulator.

See how tall the plants have grown in the greenhouse.
The electric heater was at the end of the greenhouse for the first two winters, but I now need that space so we put it on the side.

The electric heater has an automatic thermostat. We set the propane heater on the lowest setting because it has a mechanical thermostat.

Propane heater for the greenhouse. Bill thinks he bought it a little large.
Propane heater for the greenhouse. It’s now three years old. See how we set it up on bricks to keep it out of water and off the cold floor?

We did run out of propane once last year which is why we have the backup electric heater. If the electricity goes out in a storm, propane is the backup plan.

We watch the condensation line on the propane tanks to see how much is left. We also have a gauge, but remember gauges break. You also must watch the condensation line, but it only appears when propane is burning. So, if you’re having a warm day, you won’t see it. We also have a thermometer we can read from the house so we know the temperature inside the greenhouse whenever we look out the kitchen door. If the temperature drops below 40 degrees, the tropical cuttings I took in fall probably won’t recover. Heat is the most important factor of the greenhouse operation. Normal temperatures run between 50 and 60 degrees F. I could make it warmer, but then, I’d spend more on fuel. I try to keep costs down.

Watering the tropicals in the greenhouse with my Haws Brass Watering Wand.
Watering the tropicals in the greenhouse with my Haws Brass Watering Wand.

Although I paid extra for them, the flood tables aren’t my favorite feature. You need a large tank sitting beneath the benches to flood the benches. As you can see in the photos above, I need this space for other things like pond plants now that we have a pond. We hired a company to bore under the driveway and tie in a water line to our well. Inside the greenhouse, we installed a frost free faucet and shortened a garden hose that reaches only to the cold frames outside. I then attached a Haws V360 All Brass 24-Inch Watering Wand with Ball Valve and Rose, an extravagance, but I love it. It wasn’t very expensive to bore under the driveway because we traded out the work with some friends. Bill said that at retail it would probably cost $200 or so. I can now flood the tables if I want with the want, or just spray the plants with water every few days. I do like how the flood tables hold the water beneath the plants for a period of time before it drains into the brick floor below.

These are the vent and flood table controls. I keep the vent controls turned off if the weather is very cold.
These are the vent and flood table controls. I keep the vent controls turned off if the weather is very cold.

Don’t build a greenhouse unless you have someone handy around to figure out what’s going on at any given time. Ice storms can make the vents that open on top of the roof stick and and tear up the gears inside. That was last year’s fun. Bill spent most of a cold winter’s day fixing the gears when that happened. If you’re expecting an ice or snow storm, or any extended cold period, go ahead and turn off the automatic vents. If they stay closed, you won’t tear up your greenhouse and will save money on heat. Also, the vent control batteries always seem to go out on the warmest day of the year, or if we have extended cloudy weather, i.e., most of February. The batteries are normally charged with a solar panel, but we have a small battery charger as backup. You don’t want your plants to fry or freeze.

Amaryllis soaking up the sunshine in the greenhouse. I want it to bloom by Christmas.
Amaryllis soaking up the sunshine in the greenhouse. I want it to bloom by Christmas.

Because the greenhouse is heated, you need to water plants every three or four days. One of the joys of greenhouse growing is the ability to stage how quickly forced bulbs grow. If they are growing too slowly in your house, you can always take them out to the greenhouse for a spurt of growth. All of the sunshine is captured by the greenhouse. Even though temperatures in your home are warmer, sunshine wins every time. I started my amaryllis late this year so I put several pots outside in the greenhouse to get a jump on things. I’m also growing paperwhites that don’t stink like ‘Ziva’–which I hate. This year I’m growing ‘Ariel,’ ‘Early Pearl,’ ‘Erlicheer,’ ‘Cheerfulness’ and ‘Nir.’ All are growing well except for ‘Early Pearl.’ I haven’t a clue why it’s not growing yet. I put it in the greenhouse to see if that will get things started. Here’s my other post on how to force bulbs. I’ve read that ‘Erlicheer,’ ‘Early Pearl’ and ‘Cheerfulness’ need two to three weeks of refrigeration before forcing so I did that. Here’s more information from Old House Gardens about forcing bulbs indoors. This winter I also bought prechilled lily of the valley pips to force indoors for later winter because I get a little sad after the holidays. It’s pricey, but well worth it for those of us who can’t grow these fragrant flowers outdoors.

About the bugs…a greenhouse environment is perfect for insect production too. I have trouble with fungus gnats, but my friend, Layanee, of Ledge and Gardens, suggested I put gravel on top of my soil to prevent them. I use chicken grit, and it helps. I also find black aphids on my citrus. When they show up in late winter, I drench the stems and leaves of the orange tree to drown them. After the foliage is dry, I then spray the tree with neem oil, or another organic insecticide. It keeps them down to a tolerable level, and I have oranges this year. The other big pest I have in the greenhouse are the mice. I use mouse traps to keep them from digging into larger plants and burrowing down into the soil. I like these Tomcat heavy duty mouse traps because I don’t have to touch dead mice. I find peanut butter to be the best bait.

'Republic of Texas' orange tree that grows in the greenhouse over winter. The oranges are very good.
‘Republic of Texas’ orange tree that grows in the greenhouse over winter. The oranges are very good.

What else would I tell someone about owning and operating a greenhouse? Before you build it, buy a kit that is two times larger than you think you’ll need. My greenhouse is always full to overflowing by the end of the season. I now want a Meyer lemon tree and a variegated Pink Lemonade tree, and, on Matt Mattus’ of Growing With Plants suggestion, a ‘Nagami’ kumquat to join my orange tree, but I don’t know where I’m going to put them. Bill says we’ll figure out someplace. I love that man.



  1. Matt Mattus says:

    Hi Dee, Great post, I know I too get many requests on what it takes to choose and build a greenhouse. It’s also good (or not?) to hear about similar crisis’ like freezing accidents, how to run water to a greenhouse and back-up heaters/broken gas regulators. It’s a real daily concern in the winter, but we wouldn’t have it any other way. And yes, having a someone around who can build and fix things quickly is essential! Thanks for the link~! Happy Xmas to you and your family!

  2. Wonderful posting, Dee! I have a unique potting shed with some greenhouse features: one side of the roof is glass (well fake glass), small heater, wonderful long potting bench, so I am able to put seedlings there in early spring to get a jump start on annuals and veg. I will never own a real greenhouse — the cost is prohibitive — but enjoyed yours vicariously today. P. x

  3. Nell Jean says:

    A cat. Mine loves the greenhouse and we don’t have mice.

    We are about to pot up Hyacinths that chilled for 10 weeks..

  4. Rose says:

    First, I have to say that Bill is a gem! Great advice, Dee, for anyone thinking of building a greenhouse. It’s a dream of mine, too, but I doubt I will ever have one. Around here, the strong winds have destroyed several greenhouses, and that’s always been a deterrent for me to consider a small one. I would think that’s a problem in Oklahoma, too?

  5. When I took horticulture classes at the community college I was able to spend 3 quarters working in the greenhouse. I was even able to design a class on propagation where I was able to use the green house during the winter. Since that experience I have been trying to figure a way to build my own…So far I am still in the planning stage.

  6. Thanks for the reality check … and the great information. Maybe someday I’ll have a greenhouse. I have a few plants in our sunroom, and I’ve noticed the same thing about the temperatures vs. the sun. Even though the temps in the sunroom stay around 50-65, it’s sunny all day and the plants really thrive in there. I’m experimenting with potted hardy succulents this year. Last year, I left them on the screen porch, and they didn’t like the spring freeze/thaw. You’re fortunate to have some handy helpers for the building and maintenance. Your greenhouse looks great, and I imagine it’s a wonderful place to spend time on a sunny winter day. 🙂

  7. gardenannie says:

    Yes, I coveted your greenhouse and cold frames when I saw them. I gave a greenhouse – a little smaller than yours. It is one of those plastic pop up ones that you put up like a tent. We almost had a divorce over that! It holds my “indoor” plants and some room to pot up cuttings and plant seeds. Hard to find a place in the piney woods where it can get sun. We use an electric heater (we don’t get as cold as you) but I need a propane heater for emergencies. We are always losing power when limbs fall on power lines. Love living in a forest!

  8. Frank says:

    What a fantastic headache! You got me all excited and won me over with the oranges, but then the realities of running the thing cooled me off. Someday but for now I’ll have to keep enjoying it through you!

  9. I love your greenhouse! I concur about getting one that is larger than you think you will need. Also, the kit I bought (about 10 years ago) the instructions were in Dutch so we had to rely totally on pictures and thank heaven for pictures!! We laugh about it today, but then I thought my husband was going to light a match to it all and be done with it. It is a great retreat, though, when it’s cold outside and I love the smell of potting soil on a cold, winter’s day.

  10. Yes, I have always wanted a greenhouse. Just seeing the picture of yours makes me green. Even with all the warnings and negatives I still want one. I enjoy hearing about your greenhouse experiences no matter if they are positive or negative. The pictures take me there. I have never seen a bloom of a string of pearls. I think I could almost smell it though.

  11. liz piccione-volger says:

    Three times the size you think you need? Sounds good to me. That way you can put a little chair and table in there and take a minute and enjoy!

  12. Kim says:

    That is such a wonderful greenhouse and yes, all gardeners crave one. I have a “greenhouse” but I use the term in its most broad sense. A zippered vinyl box can hardly be called a greenhouse. But at this time, it has to do.

    1. Dee Nash says:

      Hi Kim, yes, that’s a greenhouse too. We’ll do almost anything to protect our plants won’t we? Have a happy winter gardening.

  13. Patti Ingram says:

    Nice article! I would love a greenhouse at some point, and this is very helpful. The paperwhites comment cracked me up, because many years ago I forced some at Christmas time because Martha Stewart said how wonderful they were…they reeked and my husband was NOT happy. No more paperwhites for us. When you say they don’t stink, do you mean they smell good or don’t have much scent at all? Thanks for the info!

    1. Dee Nash says:

      Patti, they all have some scent, but none of them smell bad. They have a sweeter scent and some are less scented than Ziva. Ziva is pretty outside, but I hate it inside.

  14. Leslie says:

    I did not know string of pearls blooms were fragrant! Since mine bloom outdoors I have never noticed. I learn new things from you all the time…thanks!

    1. Dee Nash says:

      Leslie, until I had a greenhouse, I didn’t know they were either. They smell lovely though.

  15. Excellent, informative post. So few people explain the “gotchas” of a greenhouse. Thank you for doing so!

    1. Dee Nash says:

      Thanks Kathy. I’m glad you liked it. It’s only taken me three years to get it written. Haha.

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