Sun Valley Home and Design / Spring 2008 / Greenhouses

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Greenhouses

Indoor Growing

(page 2 of 2)

Questions and Answers:

Question:
What is a greenhouse and what is the purpose of a greenhouse?

Answer:
Greenhouse construction for sustenance is growing.Utilizing the greenhouse concept and understanding our climate allows us to create micro environments in which plants generate. A simple greenhouse may be a “grow hole” that is excavated a few feet into the earth, partially filled with compost, planted, and covered with a glazing material. Glazing material is typically glass or plastic. Cold Frame greenhouses are constructed tents or framed boxes of glazing material. They are placed over a section of plants in the garden, and the design allows them to be removed or replaced as weather presents itself.
—John Benson, Webb Landscaping

Question:
Are greenhouses for keeping plants in forever or is the object to get them moved outside?

Answer:
Some tropical plants may stay in the greenhouse for their entire life, but the general objective is to move plants outside. Most homeowners use their greenhouse to extend the season, to get an early start or to extend it in the fall, or both. They start bedding plants and veggies early from seeds, and when the weather is warm enough they move them outside.
—Sun Valley Garden Center Staff

Question:
How do you help plants cope with the transition from greenhouse to garden?

Answer:
They need to be hardened off by moving them into the great outdoors when the weather is warm for quite a few consecutive days and generally the danger of frost has passed. They should be kept in a protected area out of direct sunlight where their leaf and stem tissue can toughen up. Outside temperatures, especially nighttime temps, need to be watched during the entire season, since frost is often just around the corner. Greenhouses can also be used to extend the season in the fall if you move container grown plants into your greenhouse before the first frost.
—Sun Valley Garden Center Staff

Question:
How do you maintain the humidity inside a greenhouse and how does that intermingle with how you feed plants?

Answer:
When I water, I am not careful at all. I spill it over onto the heated brick floor, which holds water. You don’t want your plants in standing water, so don’t use any trays under them. But with the running water, some plants get an iron deficiency. If the leaves turn yellow, you need to add iron to the soil. I fertilize in the fall, and then give them a rest and then hit them again in mid-January when the plants appear to be booting up for spring. Plants go on the length of light to determine if it’s time to fruit or blossom and that’s when I fertilize. You learn how to feed each one by touching the soil and checking the leaves. Most plants will show neglect after three days without water. When it’s time to take them out, I tend to choose a cloudy day so they don’t burn up.
—Lynn Clarke, master gardener and designer of large gardens and greenhouses

Question:
How is the warmth of a greenhouse generated?

Answer:
In our climate, constructing greenhouses and incorporating solar greenhouse design ideas is beneficial because they:
    • Have glazing oriented to receive maximum solar heat during the winter.
    • Use heat sinking/storing materials to retain solar heat.
    • Have large amounts of insulation where there is little or no direct sunlight.
    • Use  glazing material and glazing installation methods that minimize heat loss.
    • Rely primarily on natural ventilation for summer cooling.
– John Benson, Webb Landscaping

Question:
How do you keep the delicate balance between good bugs and bad in your greenhouse?

Answer:
 I have trouble with scale, mealy bugs and sometimes aphids. Spiders are your friend. The greenhouse is where all the bugs want to live because it is warm and attractive, but in one of our green houses we have finches and a frog and so we use organic sprays for insect control. Just before I bring the plants in for the fall, I will wash the leaves with soapy water to wash off any larvae and then spray them with dormant oil. There are systemic control methods that go into the roots and make the leaves toxic, but you can’t use that on a lemon tree because you want to use the lemons. If you get a plant with aphids, put some plastic over it so it doesn’t leave a trail on the way out and throw it away. These will explode on the environment and it’s better just to get another plant. Just preen and look over your plants and look for trouble spots. I wash the leaves weekly. You also should know if you have self-pollinators or plants like tomatoes that will need a little help because for the most part, this is a sterile environment. But try everything. It’s the only way to learn.
—Lynn Clarke, master gardener and designer of large gardens and greenhouses