Growing plants in the greenhouse

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

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.