Saturday, January 1, 2011
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!