I hope your permission slips are signed. If so, take a seat on the bus and let’s get ready to go. Quiet discussions are encouraged, rowdy behavior is not. Don’t know where we’re going yet? To an educational greenhouse of course – i.e., a greenhouse that is part of a local community college. A place to learn about growing plants and fish. A place of chemistry and mystery.
The weekend after Thanksgiving my aunt and uncle took us on a tour of a greenhouse where they are taking classes. I have never spent any time in a “commercial” greenhouse. I have only been in those attached to garden centers or nurseries; places generally used to display plants more than grow them.
I really want a greenhouse someday. A place to grow vegetables year round or almost year round. A place filled with light and humidity. All this is presupposed by my being somewhere where a greenhouse makes sense, say Oregon, Maine, upstate New York or Vermont, or a place with a similar climate. I cannot imagine how ridiculously hot one would be during the summer here in Phoenix. My AC costs enough in the summer without being inside a glass house. Yikes.
I had my preconceived notions of greenhouses before I went. In my mind I envision a glasshouse over the ground with plants in the ground or seedlings on tables. That idea proved to be along way from reality compared to how this greenhouse is run. I have never had any experience with hydroponics or any of the derivative methods the school teaches. I have heard elsewhere that a properly functioning hydroponic system uses less water than plants in soil.
When we were there the class was trying to get the poinsettias to tun red for a holiday plant sale. Hopefully they will succeed in time.
I really like the idea of 3D growing – growing in stacks of planters to maximize utilization of the vertical space. I like the idea of growing lettuce in water without soil. I have long thought of growing lettuce in large fish tanks. If done correctly the fish waste can fertilize the plants and the plants can help keep the water cleaner. The moderate temperature water should be able to help moderate the temperature of the air for the plants, allowing both to thrive.
One of the things that became very apparent is how much science is involved. There is a lot of math and chemistry because all of the nutrients the various plants need have to be added to the water in hydroponics. It is amazing how much of this I don’t even pay attention to with growing plants in dirt. I use a basic fertilizer and compost and things seem to grow. It gets even more complicated when an entire class is taking care of the plants and trying to keep everything organized and neither underfed nor overfed. There is also a lot of engineering involved, whether water lines and pumps and keeping the greenhouses the right temperature.
The students were learning about different methods of growing plants in greenhouses so there is a wide variety of methods of cultivation. The chard and lettuce were being grown by numerous methods – ebb and flow, in the vertical trays, in a gravity fed system and in constantly cooled water. Some of these seemed like more work than others and the cooled water seemed to have a very positive effect on the lettuce.
The vertical racks were being used for all sorts of plants. There were flowers, greens, tomatoes, and squash to name a few. Other than the large tomato and cucumber plants in another greenhouse, I think I liked the vertical method the best.
The method primarily used to grow tomatoes and cucumbers is entirely different from anything I have experienced before. Even the method used to support the plants is different. The plants are in a soil-less mix and a rope hung from a rafter is wrapped around the plants as they grow. The plants are then slid down the tray and the vines laid into the area next to the tray. Needless to say these are not the same varieties as are being grown in my garden. I bet these tomatoes can get 20+ feet long in no time. The tomatoes can be pollinated by shaking the support string some. The cucumbers have to be pollinated by hand. I assume the really large commercial greenhouses either have bees inside or have another way to pollinate a huge number of plants.
One of the techniques my uncle is experimenting with is grafting tomatoes. Heirloom tomatoes often lack the robust and disease resistant rootstock that many hybrid tomatoes have. There is a variety of tomato, I think my uncle is using ‘Maxifort’, that has a great rootstock but not so great tomatoes. Basically, you start the Maxifort and heirloom tomato at the same time and when they are still very small, you make diagonal cuts through each. The top of the heirloom is clamped to the bottom of the Maxifort. You can see how small the clip is in the photo. They are very small and soft silicone. As the plant grows the clamp releases. We could see where the graft happened when we were close to the plants, although it is hard to see in the photos. I think this is a technique I will try in a couple of months for next summer’s garden.
Awhile back I mentioned I was trying cloning some tomato plants. All of them eventually died. I have also recently been starting some seeds to grow a few plants in Phoenix this winter. The first set of seeds did ok, at least until I moved them for Thanksgiving. I then planted additional seeds. The first set of seeds are doing much better than the second. I think the only real difference is that the first time I could cover the seeds to keep humidity levels higher to help the seeds. I could not cover the seeds the second time because I had different sized, and larger, plants. I think this is what happened to my seed starts last winter and why I had so much trouble. This winter I plan on making/buying a new system to keep the little plants in a more humid environment without having to over water them.
One of the greenhouses is also being used to grow fish. Growing fish is something I understand having previously worked in aquaculture . I grew shellfish with different methods than used to grow fish in the greenhouse, but I generally understand what is happening and why.
It was a great afternoon and we all learned a lot about commercial methods of growing in a greenhouse. I hope it is the first of many field trips we get to go on. Maybe next summer we will be able to tour some farms also.