Published in the Dec. 1995 Fruit Gardener Magazine
Lush crops of basil grow alongside roses, culinary and medicinal herbs and yew trees in an otherwise unused mine shaft 1,170 feet down, in Flin Flon, Manitoba, Canada. In a part of Canada where mid-winter temperatures can plunge to -40 Fahrenheit, this experimental plot, deep inside the earth, provides fresh herbs to local restaurants and bouquets of roses for the miners to take home to their wives. The underground garden may also provide a solution to the serious depletion of an essential plant-derived pharmaceutical product called taxol.
It all started when Wayne Fraser, Director of Environmental Control for The Hudson Bay Smelting and Mining Company, had approached a local economic development group called Greenstone Community Futures. He had thought of working with this association to develop surface greenhouses heated by waste air. The nature of the mining operation in Flin Flon requires that outside air be piped into the shafts for purposes of ventilation. In winter this has to be heated because, although ambient temperatures are quite warm far below the surface, the outside air coming in can be as cold as -30 to -40 Fahrenheit which chills everything down way too much. After passing through the mines, all that expensively heated air is then exhausted out to the environment, and Fraser thought there might be a practical use for it.
Meanwhile, further west in Saskatoon, Saskatchewan, Brent Zettl of Prairie Plant Systems, was doing micropropagation and biotech work with native fruit crops such as saskatoons and chokecherries. "We needed growth chambers and they had ample space for potential development. They have, in their mines, the equivalent available space of 70,000 houses...that is, comparable to all the houses in Saskatoon combined."
One individual from Greenstone knew of Zettl's work, knew Wayne, and arranged for their first meeting. The original intention of using waste heat from the mine somehow shifted and evolved. Both agree that setting up an experimental growth chamber deep inside in the mine was Fraser's idea.
At present, this underground greenhouse consists of roughly 1000 square feet. Twenty lights provide illumination. Ten of these are metal halide types. The rest are sodium lights, the same kind of orange lights you see in parking lots. Together they provide a broad spectrum comparable to natural sunlight.
Instead of using heated waste air, the growth chamber depends entirely upon natural geothermal heat. Fraser explained that the deeper you go into the earth, the hotter it gets. He described mines in South Africa, 10,000-12,000 feet deep, where the temperatures soar to 120-130 Farenheit, far too hot for any plant. At 1,170 feet down, the ambient temperature is 55 Farenheit. The entire mine itself is well over 4000 feet deep. Fraser agrees that potential exists to grow hotter-climate plants farther down, where even tropical fruit species could thrive with no supplemental heating, but there are no plans for any such project. Additional heat comes when they turn on the lights. These raise temperatures into the high 70s, a heating-cooling cycle which mimics nature, in which the temperature drops at night and heats up during the day as the sun rises.
Computers play an essential role in maintaining a perfect growing environment. According to Fraser, "We monitor factors such as humidity. We control the on-off cycle of lights. Devices in the soil tell us when plants need water and when they don't. We can activate drip irrigation and misters, and fertilize. All of this is controlled by computer."
Although not everything grows well under these conditions, those that thrive do amazingly well. Basil, in terms of product per square foot, produces 6-10 times as much as when grown in surface greenhouses. The plants become larger, mature faster, and yield larger crops.
Woody plants also do amazingly well. According to Zettl, saskatoons, evolved to deal with central Canada's harsh climate, positively luxuriate in the perfect growing conditions provided. Yew trees showed a tremendous growth rate compared to those found in natural settings. Zettl mentioned that scientific types who haven't yet seen the results for themselves tend to disbelieve him when he tells them that the yew grew 200% better underground.
Explanations include the atmosphere's slightly elevated level of carbon dioxide. Watering, lighting and humidity are all under perfect control, and therefore plants encounter no stressors. These factors partially, but not entirely, explain the elevated growth rate. Fraser admits that they don't know exactly why plants respond with such lush abandon. When asked if, at that level underground plants might encounter certain gasses in trace amounts, he admitted that it is certainly a possibility.
Because these plants are so far below the earth's surface, isolated, they generally suffer no insect infestations. The only time a problem like that ever came up was when some non-sterilized soil accidentally got brought in, and they had to deal with soil mites. Neither flying insects nor vertebrate pests can find their way down there.
Brent Zettl, co-creator of this pilot project, explained that humidity is maintained at 50-60%. Without the computer-controlled dehumidifier, ambient humidity would be 99%. Early on, it was recognized that, due to this high humidity level, fungus could become a problem. They have been controlling it with various fungicides; they also pasteurize their soil. This summer, they also went into a shutdown cycle, during which they removed all plants and sterilized the chamber.
Their most successful fruiting plant has been saskatoon (Amelanchier alnifolia). The three cultivars chosen for this were "Thiessen," "Martin," and "Smoky." When (after assuming hand-pollenizing) I asked what the fruit was like, in terms of volume and taste compared to that grown on the surface, Zettl explained that they weren't interested in fruit production.
One purpose was to clone these chosen cultivars to expedite the production of young plants -- that is, produce them in greater numbers and get them more quickly into the hands of commercial growers. The experiment involved taking cuttings off the mother plants, putting these into a culture jar, then seeing how quickly the newly cloned plantlets would grow afterward.
A second purpose was to isolate the mother plants used in initiating these tissue cultures. Zettl keeps the stock plants underground in order to flush them out--i.e. make them grow more quickly, to be more rapidly available for taking more cuttings.
Culinary herbs grown include sweet basil, lemon basil and rosemary that are test-marketed to local restaurants who then acknowledge the source somewhere on their menu. Given this prairie province's very intense winters, when fresh herbs are otherwise unobtainable, restaurateurs are thrilled to receive this mine-grown produce.
Pharmaceutical plants cultivated include medicinal herbs such as Arnica montana, Vinca rosea, Echinacea, both E. purpurea and E. angustifolia, evening primrose (Oenothera spp.), Levisticum officinale (lovage) and Digitalis purpurea (foxglove).
At present, Fraser and Zettl are most interested in their collection of twenty yew trees. Yew, especially Taxus brevifolia, is the source of taxol, an important anti-cancer drug. Due to demand, reserves of the plant growing wild in nature are being depleted quickly. It is predicted that, at current rates of harvest, only about 7 years' worth of yew, source of taxol, remain.
Unless pharmaceutical companies can come up with artificial sources of this drug, yew will need to be plantation grown. One promising approach is to develop yew trees with greater concentrations of taxol. According to Zettl, there at the mine they aren't actually doing any of this breeding work themselves. Their task is to foster an increased production of these increasingly rare plants, to accomplish the same growth pattern within a 1-2 year time frame that normally occurs in five years. A faster turnaround, in terms of maturity, would in turn support the efforts of hybridizers to more quickly develop better, higher-taxol cultivars. Both Fraser and Zettl agree that they intend to stick with growing yew for the foreseeable future.
According to Zettl, at present they are trading for product with pharmaceutical firms, not selling the yew. Fraser explained that at 1000 square feet, the greenhouse is too small to be anything but experimental. If their growth chambers were five or ten times larger, going commercial might become an option.
One other plant they grow successfully are roses, those flowers that have gladdened the hearts of miners' wives. Roses are part of a ascreening program that looks at potential commercial production of fresh and dried flowers; leftovers from the study are given to miners and staff. Rose bushes in bloom also look really great in the publicity photographs and capture peoples' imaginations.
Fraser also explained that, because this project is so experimental, the situation so unique, they have never done a cost analysis on greenhouse product--i.e., comparing the cost of growing a certain volume of anything in a surface greenhouse compared to bringing that same type and amount of plant material to maturity underground. The servicing of the growth chamber is artificial. For instance, the "skip" (elevator), although available for them, was installed for mining use; they really can't pro-rate the cost of access. The additional expense of running lights and providing water is relatively modest compared to that of heating a surface greenhouse during Manitoba's harsh winters.
Although they enjoyed spectacular results with certain plants, others proved to be clunkers. Tomatoes and potatoes, for instance, performed badly. Although they did not really put much energy into investigating the cause of these failures, Zettl speculates that the environment was just too rich for certain species, that these plants were trying to grow too quickly and as a result built up too much internal photosynthate.
He mentioned another interesting tidbit: plant species that evolved later did less well than those of more ancient lineage. He speculates that the slightly elevated carbon dioxide level in their growth chamber might replicate the natural atmosphere found in geologically ancient times. There used to be more atmospheric carbon dioxide back then than at present. Older species, having originated under such conditions, appear very comfortable, whereas those evolved during modern atmospheric conditions, such as tomatoes and potatoes, simply could not adapt.
When asked to describe the disadvantages of growing plants way down below earth, Fraser explained that since the greenhouse is in a part of the mine that continues in use, conflict sometimes occurs between the needs of the greenhouse and mining operations. Access can be a problem because the skip is part of the mining production process and is not always available.
To Zettl, the project is successful because everyone from the senior executives to the guys working the mines support the program; they are interested in it, and they get the products that come out of it. With that willing cooperation, the needs of the growth chamber dovetail with the existing operation. Without this level of support, such a greenhouse would have been impossible.
One reason for everyone's interest has to do with job creation or potential job creation. Another is simply that this greenhouse, so far underground, has captured everyone's imagination.
According to Fraser, at present, there are no immediate plans to expand although, if they did, widening operations would be relatively cheap. The computer system, most expensive component of the whole project, is already set up.
Zettl replied, when asked if he prefers the mine shaft garden to surface greenhouses: "It is interesting and unique to travel there ... more bells and whistles to get to the chamber. That's part and parcel of the romance of it. But both are good."
copyright Alice Ramirez, 1995
Reprint rights available
Go on to Maldive Mystery
Return to Garden Writing
Return to Alice Ramirez Homepage