Saturday, January 1, 2011

The Greenhouse

Recently I was interviewed by the producers of a public television gardening show, for an upcoming episode about greenhouses.  All in all it was a fun experience, I discovered that it takes as long to film five minutes of finished programming as it does to grow a zinnia from seed to bloom!

In any case, there were several things we discussed that day that the interviewer felt were worth sharing.  I would guess that many readers of this blog have experience with indoor growing, so it's probably repetitive information; if not, however, feel free to use whatever you might find interesting and helpful in your own gardening adventures!

Many people assume that “a greenhouse is a greenhouse is a greenhouse.” In the same way that plants have different requirements during the outdoor growing season, their needs during the winter vary widely. One of the greatest challenges with the greenhouse is maintenance of differences in light, moisture levels and temperature.

With the possible exception of real tropicals, most plants need a winter dormant period. In the greenhouse, we try to duplicate the winter conditions of the particular plant’s native habitat. One of my first projects upon buying a non-hardy plant is researching the conditions of that plant’s native habitat, so that we can duplicate that as closely as possible.

We do our best to water the greenhouse plants with room-temperature water, though that isn’t always easy. We use a well for irrigation at the Big House, so in winter (even in Georgia), what comes out of the tap is icy cold. That can be a “death sentence” for a tropical plant!

Pests are a real issue in any greenhouse, and need to be handled quickly. If there is any one job that takes the most time in the greenhouse, it is the treatment of pests, with the most gentle (but effective) methods we can employ. We generally start with mild dish soap, then will progress to alcohol, fly paper traps, etc.

Whatever the size of the greenhouse, we always need to look at the cost-effectiveness of overwintering plants. Certain jasmines, for example, are (in my experience) “scale magnets” and something that we just don’t overwinter; some of the tropical hibiscus plants are also just not cost effective to overwinter in many cases. For the amount of space that they require (and their inconsistency in staying attractive), it is often less expensive to buy a great new plant in the spring.

A greenhouse of any size is both fun and challenging for a gardener, and one that I would encourage anyone to try if given the opportunity!


  1. fascinating. What percentage of the tropicals do you replace?
    Is this a national garden show? When will it air?
    Can I have your autograph? :)

    Happy New Year, Tim

  2. Sounds like an incredible amount of fun experience. I have always thought about a greenhouse if I ever moved back to the fact, it would be a requirement....just never thought about the bugs being an issue though. For me, it would be difficult giving up my citrus crop here in Tucson....nothing like fresh fruit off the tree all times of the year.

  3. Please don't assume that all your readers know what it is like to garden in your climate or about glass houses. In temperate southern Australia they are, to this gardener, an exotic and romantic idea. I long for a conservatory to sit in...but the climate just isn't conducive. I enjoyed this post. A link to the said garden show would be interesting if it is possible too.

  4. Your greenhouse is gorgeous! Thanks for the great tips.

  5. One of my favorite aspects about having a greenhouse is the warm, sunny time it allows me while outside is freezing cold. Working in shirt sleeves, with growing plants, is real medicine in the depths of winter.

  6. Love the new header and the greenhouse! Happy New Year.

  7. It is all information to be absorbed. Great blog.