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MMWD Blog: Think Blue Marin

Welcome to our blog! Written by staff at MMWD, “Think Blue Marin” explores all things water in south and central Marin—water supplies, conservation, new projects, watershed management, and more.

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Feb 04

The Golden Years

Posted on February 4, 2016 at 2:48 PM by Ann Vallee

by Charlene Burgi

In titling this blog, I'm not referring to signing up for social security, submitting for retirement, or considering a move to senior housing.

The "golden years" I speak of are in reference to the history of greenhouses. The need for greenhouses grew rapidly during the 18th and 19th centuries, as explorers hunted down exotic and unusual plants. During the Victorian era in particular, plant-seekers scoured countrysides around the world in search of unique plant material. These treasures of the vegetation world prompted propagators to develop the finer art of increasing their bounty from the mother plants. This in turn expanded the need for healthy environments in which to grow these new plants.

Unlike our makeshift greenhouses of today, the Victorians took great pride in the design and construction of their greenhouses. They perfected the ability to control temperature, moisture, and light to achieve optimum growing conditions. While many of their attempts were trial and error, many of their ideas are still used today.

 Cold frame
For example, they dabbled with cold frames and hotbeds to increase available heat. The cold frames utilized sunlight, collecting radiant heat to protect plants in the middle of winter. Hotbeds, on the other hand, took advantage of the heat from the composting process. (I find it fascinating that a friend's husband implemented a hotbed in their greenhouse this year, and their plants are thriving without additional heat source.)

A hotbed can be made by constructing a 3-foot-high bed in the greenhouse. The box can be made up of straw bales, which are good for a year before they decompose. Hotbeds also can be built with 2 x 12 wood (not pressure treated) or concrete blocks for a more permanent structure. Once the box is constructed, backfill using an equal part of leaf material and fresh manure (found at your local stables or dairy farm—they are usually thrilled to have it hauled away).

If you remember how to make compost, you will want to mix the greens (leaves) and browns (manure) together, then add water to begin the microbial process that creates heat. Allow the bedding to sit for a few days for the ammonia to dissipate. I would first broadcast radish seeds into the bedding material to make certain the soil bed isn't too hot. Once the radishes come up, plant directly into the hot bed, then cover the bed with a sheet of plastic or shade cloth at night to retain the heat. Do not allow the sheet material to come into contact with the plants. You may want to invest in a fiberglass sheet for rigid coverage.

Conservatory of Flowers
Conservatory of Flowers, San Francisco (by J. Ash Bowie, CC BY-SA 3.0)
We can learn a lot from our forebears. Have fun with this project. Let me know how it works for you.

For fun, take a day trip to the Conservatory of Flowers in San Francisco to see a beautiful Victorian greenhouse at work.


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