The rooftop greenhouse officially opened with a ribbon-cutting ceremony on the fourth floor of the University of Arizona’s Student Union Memorial Center on Wednesday, Feb. 27. Though the greenhouse’s first harvest took place in October 2018, the team behind the greenhouse celebrated its success with a ribbon-cutting ceremony and reception. In attendance were greenhouse project and production manager Stacy Tollefson (far left) and Senior Director of Arizona Student Unions Todd Millay (far right). The actual ribbon-cutting was performed by Bridgette Nobbe, the graduate assistant for Campus Pantry (center left), and Michaela Davenport, the director of the Campus Pantry (center right).
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The rooftop greenhouse is a completely soilless operation employing hydroponics, according to Tollefson. Tollefson is also an assistant professor of practice in the Biosystems Engineering Department. She led the tours that explained the greenhouse’s system to community members. Instead of soil, plants in the greenhouse are grown in rockwool, which is made from spun volcanic rock. Rockwool does not have any nutrients, so Tollefson and her three student-workers must give the plants water and soluble fertilizer. The nutrients are housed in two tanks inside the greenhouse. Every day the tanks deliver nutrients to the plants for three minutes before shutting off for 20 minutes and repeating the process. According to Tollefson, the key to hydroponics is a “little bit of nutrient water, but frequently.”
Using hydroponic techniques, Tollefson and her team grow produce in the greenhouse using an estimated 5 percent of the water and 10 percent of the land needed for an on-the-ground garden. The water and nutrients delivered to the plants exist in a closed loop, and most of the excess water ends up back in the system. According to Tollefson, this closed loop means there is very little water waste. Because the plants are housed in the greenhouse, Tollefson and her team are able to grow plants all year long. Sensors inside the greenhouse test for temperature and humidity, so the plants are not at the mercy of outside weather conditions. According to Tollefson, tomato harvests take place 10 months out of the year before the plants need to be replaced.
Student involvement is a strong part of the rooftop greenhouse. Back in April 2017, five UA students won a contest to have their designs used in planning the greenhouse. In total, 125 students entered. Three students currently work with Tollefson (left) in the rooftop greenhouse. One of those students, sustainable plants systems major Devon Valdivia (center) outlined his work in the greenhouse. He is in the greenhouse four or five times a week, keeping an eye on the closed system used to deliver nutrients to the plants and monitoring the plants’ water usage. Valdivia first got involved in the greenhouse at his professor’s recommendation. Valdivia has worked in the greenhouse since the beginning of this year. Tollefson and the students also collect data from specific blocks of plants in the greenhouse as a sample to check the condition of all the plants. She and her team even hand pollinate the plants using electric toothbrushes.
Currently the garden grows cherry tomatoes, slicing tomatoes and cucumbers. Harvests occur once a week. According to Tollefson, around 15 pounds of cherry tomatoes, 30 pounds of slicing tomatoes and 430 pounds of cucumbers are gathered weekly. The rooftop greenhouse is one of several greenhouses the UA operates. Tollefson recently applied for more funding from the UA Green Fund and the Student Services Fee to expand greenhouse operations. Should the request be approved, she said she plans on expanding two larger greenhouses on Roger Road, where they would be able to grow lettuce and the other types of produce.
All the produce currently grown in the rooftop greenhouse gets donated to the UA Campus Pantry. The Campus Pantry provides food to anyone with a CatCard and is open every Wednesday and Friday. According to Nobbe (left), the graduate assistant for Campus Pantry and a second year higher education master’s student who spoke at the greenhouse’s opening ceremony, 29 percent of UA students reported being “food insecure” at some point in their college careers, and she expects that number to increase. Davenport (right), a junior studying philosophy, politics, economics and law, also spoke at the opening ceremony. She said Campus Pantry served 550 students last week and remarked, “students can’t be students if they’re hungry.”
Prior to and after the ribbon-cutting, a reception was held where team members and members of the public were able to mill around and sample dishes, some of which were prepared using produce grown in UA’s greenhouses. According to chef Michael Omo, the lead chef for the event, an effort was made to stick to the garden party theme and “showcase urban farming.” A focus was put on the freshness of the food. The cucumbers on this avocado toast (bottom) came from the rooftop greenhouse itself.
Cucumbers from the greenhouse were used in some other creative ways. The signature drink for the reception was a cucumber-lime mojito. Vincent Tarantola, who works with Pinnacle Concessions Special Event Division and bartended the reception, said he probably use about a dozen cucumbers to make the mojitos that night. He also said it tied nicely into the theme of the party.
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As parting gifts, guests could take home seed packets and live succulents. For UA students who want to get more involved in the rooftop greenhouse, Tollefson runs Sustainable Urban Agriculture Internship Program. Food-insecure students can access food harvest from the greenhouse at the Campus Pantry. Tollefson said that should the greenhouse ever produce more than needed, they would give the excess produce to the restaurants on campus, but for right now, the harvest matches the express need from the student body.
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