What’s so Special About Controlled Environment Agriculture Cucumbers and Corn?

What’s so Special About Controlled Environment Agriculture Cucumbers and Corn?

In, July 2014, I wrote an article on “Indoor Agriculture: Opportunities to Imagine.” In it was a discussion stating that as Earth’s human population reaches nine billion by 2050, current agricultural systems and practices may not be capable of feeding everyone.

It’s All in the Terminology

Controlled Environment Agriculture (CEA) has become nearly a household term during this decade. That’s not to say CEA is new, but rather it has become significantly more visible in research, teaching, and consumer awareness.


The agriculture community has made progress in educating urban, suburban, and rural consumers about the ultimate importance of future food production to every person on the planet. Still, more education and collaboration are needed between farmer and consumer. That aside, consumer awareness and interest in CEA’s emerging applications for indoor (warehouse) agriculture, greenhouse production, and urban agriculture in general signals impressive progress.

To be clear, CEA includes greenhouse production. Any of us growing crops in greenhouses, ornamental or edible, are indeed controlled environment agriculturists as, by definition, horticulture is a branch of agriculture. While indoor agriculture is receiving much of the attention, greenhouse production will also play an important role as we meet the challenge of feeding nine billion people.

Feeding the world is not a zero-sum game where one system of food production will become the only system. Industrial-scale field agriculture will maintain a significant share of global production due to sheer food volume necessity. While sounding contradictory, applying sustainable practices to our industrial model will help. But supplementing and complementing industrial output with greenhouse and indoor production located in and around urban consumption centers will be required. With these comments as today’s backdrop, let’s talk about cucumbers and corn.

How CEA Cucumbers Are Grown

What’s so special about the cucumbers shown in Figure 1 (see slideshow)? After a quick glance, most would respond that there’s nothing special about them. Some might suggest that they could be darker green, or that they’re not straight enough, or should be more uniform. All are accurate and welcomed comments, but they’re not the correct answer. What’s different about these three cukes is that they were harvested from plants grown without a single photon of sunlight.

Greenhouse and indoor edible crop production revolves around proper cultivar selection. The cucumber ‘Salad Bush’ was used in this experiment and was provided by Harris Seeds, Rochester, NY. As implied by its name, this cultivar is a dwarf, bush-type vine growing to a length of three feet.

Figures 2 and 3 (see slideshow) show the indoor growth room equipped with 2-foot-long light emitting diode (LED) light fixtures. During early seedling growth, the fixtures were hung above the young plants in a traditional horizontal orientation. As the vines developed, they were trained along bamboo stakes mimicking traditional greenhouse-trellised cucumber production. The light fixture orientation was changed to vertical as well to provide uniform light intensity to the vertical vines. Figure 2 shows the lights in growth mode, where red and blue diodes provide most of the light. Figure 3 shows the fixtures in view mode, where all diodes except white are powered down to allow for normal viewing.

The cucumbers were sown in plug trays on a greenhouse propagation bench and transferred to the indoor growth room upon transplant into 6-inch pots using Jolly Gardener Proline C/B growing mix (Northeast Nursery and Greenhouse Supply, division of Northeast Nursery, Peabody, MA).

Flood and drain irrigation was used to deliver 150 ppm nitrogen from a 13-2-13 JR Peters soluble fertilizer formulation. Multiple flood cycles were used as plants grew. A 16-hour daylength was used with light intensity of approximately 400 umoles of PAR via the LED source yielding a daily light integral of approximately 23 moles. Growth room temperature set point was 70°F.

What About CEA Corn?

The two ears of corn pictured in Figure 4 (see slideshow), referenced by a 6-inch chef’s knife, do not appear to be any more special than the cucumbers. Some might suggest that the ears are not long enough, that pollination was incomplete, or they should be more uniform. Again, all are accurate and welcomed comments, but not the correct answer. Unlike the cukes, these ears of corn were harvested from plants that did receive sunlight. However, the plants were not grown outdoors in a field but on a greenhouse bench in pots containing a soilless mix.

Figures 5 and 6 show the crop during production. Ten-inch pots contained three plants using the same Jolly Gardener mix as the cucumbers. Pictured is a 4 foot-by-8 foot flood tray holding 15 pots (45 plants). Accounting for overhang, the plant density for this experiment was approximately 1.2 plants/square foot. The cultivar ‘Revelation’ was also provided by Harris Seeds.

Flood cycles were adjusted as the crop developed, and the nutrient solution contained 200 ppm nitrogen,150 ppm from 13-2-13, and 50 ppm from 15-0-0. The crop was grown during summer months without night heat, with a greenhouse ventilation set point of 75°F. The temperature set point was exceeded on sunny days. Figure 5 (see slideshow) shows the crop several weeks after transplant, and Figure 6 shows the crop several weeks after that. Air movement from greenhouse ventilation facilitated pollination.

Again, What’s so Special?

Your answer to the question ‘What’s so special?’ about these two common vegetable crops may be simple, but there’s nothing special about them. Cucumbers are already a major greenhouse crop, so imagining indoor production isn’t too hard of a stretch. I agree, but still, knowing that progress is being made that will soon allow any of us as consumers to repurpose our canned-goods pantry next to the kitchen into an indoor CEA unit is pretty exciting.

Fresh salad ingredients 3 feet away from the kitchen counter will define farm to table in an exciting  way. This isn’t suggesting that commercial field, greenhouse, and indoor production will become obsolete. Remember, we have nine billion mouths to feed. We are going to need every type of sustainable food production system in the arsenal.

Regarding the corn, your answer to ‘What’s so special?’ might be that greenhouse production of an agronomic-like crop is silly and not at all feasible. Okay. But hold on a second, here’s another perspective.

For the past year, I have been working on a project with a team of engineers at MIT. The project, called OpenAg, is focused on indoor CEA. Last July (2017), the project took the MIT team and me to NASA to participate in a two-day CEA workshop. For me, working with NASA scientists and engineers was a once-in-a-lifetime, humbling experience.

Out of This World

The most jaw-dropping objective NASA presented during the two days is that we need to have food growing on the surface of Mars by 2029 when the first astronauts are scheduled to arrive. This target date is dependent upon funding, and the NASA folks repeatedly told us that support from Washington, DC, changes from one administration to the next. Nevertheless, 2029 is our next “JFK 1960s charge of going to the Moon and returning safely” rally point.

A few minor details set the stage. We were schooled repeatedly that the cost of placing something, anything, in space is exorbitant. As a plant scientist, I needed to be reminded that inputs used on earth, like water and fertilizer, cannot be put into space in the amounts needed. Much ingenuity is required. Another consequence of this reality is that we cannot afford to send much more food than will be required to get the astronauts to Mars. Before they arrive, food needs to be there, growing.

Robotic crop production will need to be there well before our first explorers arrive. That means that during this decade and the next, we’ll be practicing on the Moon’s surface. How cool is that? Does CEA corn and cucumber production seem so far-fetched with this in mind?

How does this affect any of us currently in commercial greenhouse production? Think of decades of technology from the space program trickling down to everyday life. Lightweight and strong composite metals, high-tech fabrics, Tang, freeze-dried food, cordless power tools, memory foam — we were reminded while at NASA that all these products and many others were spun from the space program.

Another recurring message in the From Flowers to Food series is that greenhouse and indoor food crop production are limited, in my opinion, by a single factor: our imagination. Figure 7 (see slideshow) is a picture that, within the next decade, might travel electronically over 30 million miles after being taken on the surface of Mars.