Growing in a Greenhouse – Dos and Don’ts

Now that we have a wonderful greenhouse, complete with lining and a doorway, I needed to research the best way to make use of the greenhouse. I don’t know a whole lot about growing plants indoors and a greenhouse adds an additional layer of complexity to growing vegetables. There are several factors that need to be controlled by me: temperature, circulation, humidity, light, and soil.

Temperature: This is one of the most important factors that can be controlled using a greenhouse. It is certainly one of the benefits that I like the most about having a greenhouse – the insulation allows you to extend the growing season of summer crops into late fall, fall crops through the winter. Hot air that accumulates in the summertime needs a way to be removed (see the Ventilation section below) or in winter a way for temperature to be warmed. Summer crops grow in daytime temperatures of 75 to 85F and 60 to 75F at night. Cool weather crops do best when nighttime temperatures reach around 50F and 60 to 65F during the day. Obviously, it will be great for us to have a good thermometer that I can check a couple times a day. Right now we have a little space heater that turns on when the temperature gets below 40F. So far, the greenhouse seems to keep the air about 10 degrees higher than outside temperature.

Ventilation & Air Circulation: The circulating of air is extremely helpful for the growth of plants. Adequate spacing between plants is necessary so that fungal infections can be prevented. Plants require carbon dioxide and this gas can be quickly depleted inside a greenhouse. A quick way to resupply this is to ventilate the greenhouse every morning and since we have a doorway, I can simply open the door to help ventilate air.

Humidity: The relative humidity of the greenhouse should be around 70 to 85%. Any higher and the risk of disease and fungal infection increases dramatically. Ventilation helps with keeping the humidity at a good level. Watering only as needed helps keep the humidity at normal levels as well.

Light: Just like a regular garden, most of the light comes from the sun. The placement of the greenhouse is significant in terms of where the sun angles into the dome. Our particular location does have a fair amount of shade in the fall and winter. This can be remedied by adding fluorescent lights. I think we could put a few lights over some of the gardens where light-loving plants are located. Obviously, you can also have too much sunlight; however, I don’t think we will have this problem. If we were to get too much sun, shaded panels can be added to block out excess light.

Nutrients: The Mel’s Mix is a good one to use for the raised gardens. Compost and vermiculite should be added in the spring and fall to amend the soil. Rotating crops is a great practice and I plan to do this as the plants finish growing. As I mentioned in a previous blog (https://greenthumbilina.wordpress.com/2014/09/01/composting-101-whiteflies-killed-my-garden/), we have a compost barrel that I have been adding organic material (old plants, egg shells, uncooked food, old paper towels, etc.) on a bi-weekly basis. I already amended the soil around the brussels sprouts and broccoli with the compost.

Hopefully, we will have a winter crop, but if not I am learning a lot for next year!

Online Resources:

http://www.organicgardening.com/learn-and-grow/tending-greenhouse?page=0,1

http://www.motherearthnews.com/organic-gardening/advice-on-greenhouse-growing

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