Progress report for FNE20-966

Exploring the Feasibility of Growing Microgreens in a Modified Cold Storage Room

Project Type: Farmer
Funds awarded in 2020: $6,376.00
Projected End Date: 03/31/2021
Grant Recipient: Fat Peach Farm
Region: Northeast
State: New Hampshire
Project Leader:
Jennifer Wilhelm
Fat Peach Farm
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Project Information


Microgreens are a popular crop with both growers and consumers. With low start-up costs, a short growing period (typically between 13-25 days), potential to grow year-round, and high retail value, microgreens are an appealing crop for farmers. For consumers, microgreens are tasty and easy to prepare, with high nutritional value. Given the potential of growing microgreens under lights in the winter, they hold a special appeal to farmers in the Northeast, where the growing season is short and farm income is low over the winter months. For this research project, we aim to (1) explore the feasibility of growing microgreens in a modified cold storage room under lights, and with supplemental heat; and (2) determine if growing microgreens in this arrangement is economically viable (profitable). To evaluate production methods, we will grow four varieties of microgreens (kale, broccoli, mild salad mix, and pea shoots) under two different light treatments (fluorescent and LED full spectrum lights). We will harvest and weigh marketable microgreens by variety and by light treatment. To assess economic profitability, we will track start up costs (shelving, lights, heater, fans, temperature controller, and CoolBot Pro), as well as all production costs including electricity for heat, fans, and lighting. Data will be shared through Cooperative Extension publications, a farmer field day on the farm, and various regional farmer meetings. This research could have broad appeal to farms in the Northeast, particularly small-scale farmers looking to increase winter on-farm income. 

Project Objectives:

Most small scale farms have cold storage rooms, which are typically only in use during the summer months to keep products fresh for market, but sit idle during the colder months. Making a few minor modifications to existing farm infrastructure (cold storage rooms) to grow microgreens, a high-value crop, could be a simple and cost-effective way of supplementing farm income. Given that microgreens can be grown vertically under lights, their production could be an efficient use of small spaces. 

We have two main objectives for this study. We aim to (1) explore the feasibility of growing microgreens in a modified cold storage room under lights, and with supplemental heat; and (2) determine if growing microgreens in this arrangement is economically viable (profitable). 


According to the US Agricultural Census, over 70% of New Hampshire farms sell less than $10,000 of products, and 68% (2,821) of the state’s farms reported net losses in 2017. Making a livable income in small-scale farming is challenging, particularly in New England where the growing season is short. For many fruit and vegetable farmers in the Northeast, farm income slows down from late fall through winter, and doesn’t pick up until mid to late spring. Many farmers grow storage crops and cold-hardy crops in high tunnels, and some farmers sell community supported agriculture (CSA) shares to increase farm income through the winter. However, for small-scale farms that don’t have production space to grow storage crops (e.g., squash, cabbage), cold season infrastructure (e.g., high tunnel), and/or where CSA’s are not economically feasible due to scale, finding alternative sources for winter farm income could help increase farm viability. 

Northern New England has a short growing season, and many small-scale farmers have low to no income over the winter months. Through this study we aim to determine the feasibility of growing microgreens in a modified cold storage room from October through April, when these rooms otherwise sit idle.  As cold storage rooms are heavily insulated, and outfitted with electricity (typically air conditioning units are used to keep the space cool), minor modifications are required to make the space conducive to growing microgreens. By adding and/or modifying shelving, adding heat- space heater and heat mats- and lights, a small space can become productive. We propose to explore if modifying an existing cold storage room with supplemental heat and lights is conducive to growing microgreens through the coldest months of the year. Microgreens are popular with consumers and have proven to be a profitable crop for farmers when grown high tunnels, but heating high tunnels through the coldest months of the year can be costly. As most farms have cold storage rooms and microgreens can be grown under lights, modifying existing infrastructure could prove to have low startup costs and high income potential, contributing to overall farm viability. Having farm-generated income during the winter could decrease the need for farmers to seek off-farm employment and potentially keep employees year-round.


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Materials and methods:

The study will take place in our cold storage room, which is 8’x7’ (56 square feet). Each 8’ wall will fit one wire rack with three shelves per rack, accommodating 24, 10 x 20 trays per rack at any given time (6 trays of each variety). Each week, 24, 10×20 flats will be filled with pre-moistened Vermont Compost Co. Fort Vee Compost-Based Potting Mix. Wet media is slow to warm up, which may affect speed of germination. To address this issue, we will use heat mats to warm pre-wet media prior to seeding. Once growing media has reach 80 degrees F, we will weigh microgreen seeds by variety to ensure the same amount of seed is evenly distributed across the prepared trays (6 trays of each variety). We will pre-soak pea seeds prior to seeding into trays to promote germination. Seeded trays will be placed back on growing mats on metal shelving, 3 under fluorescent and 3 under LED grow lights, and bottom watered as needed. Trays will be moved off heating mats once seeds have germinated. We will install lights so that they are adjustable in height based on crop stage and growth, providing added control from a growing perspective. 

As the growth of mold is of particular concern, we will sterilize growing trays with food grade hydrogen peroxide and white vinegar prior to filling with soil (following the National Organic Program list of allowed and prohibited substances). This step will be repeated after each harvest. We will address air circulation by including horizontal airflow fans to ensure good air flow. Additionally, we will seed microgreens in perforated trays and place them in Botanicare® 2 ft x 4 ft Rack Trays, which will allow us to water from below and reduce the chance of overwatering and damping off. We will also monitor humidity to maintain a 50% humidity level, and use a dehumidifier if levels rise above 50%. If, despite these preventative measures, mold should become an issue, we will use food grade hydrogen peroxide and white vinegar to treat mold on microgreens. 

A ceramic convection heater will be plugged into a CoolBot system with an Inkbird ITC 308 Temp. Controller set at 65 degrees F. Temperature will be recorded 24/7 using the CoolBot Pro. Electricity use will be recorded for lights, and heat, and fan by kWh with a plug-in kilowatt hour meter. Heat will run as needed to maintain 65 degrees F, while lights will be on 14 hours/day. 

We will create a weekly seeding rotation, seeding 24 trays each week and harvesting 24 trays each week. The table below shows weekly budget projections for potential gross income/tray and per variety for three of the four varieties based on Johnny’s Selected Seeds 2017 Microgreens Yield Trail. Each week, harvested microgreens will be weighed on a certified scale, with weights recorded by light treatment. Our budget projections suggest that startup costs could be recovered in year one.

We will measure the total cost of materials (setup: shelving, lights, heater, CoolBot Pro, and InkBird Temperature Controller; production: seeds, soil, and trays), electricity (heating, and lighting by kWh/treatment), and yield by variety. We will measure each item weekly, with one figure for setup cost.


Participation Summary

Education & Outreach Activities and Participation Summary

1 Tours

Participation Summary

1 Farmers
Education/outreach description:

To date, I have only given one farmer tour of the operation. I have developed newsletter content, which reaches an audience of 241, with an average 44.7% opens. The newsletter audience consists mostly of customers and a handful of local farmers. I have also posted several social media posts on Instagram where we have 590 followers, with 10-15% engagement. Our Instagram account reaches more farmers across a larger geographic range than the newsletters.

I will continue to update my audience via newsletter and social media, and work with UNH Cooperative Extension to host a tour of the operation specifically for farmers, either in person or virtual this March (2021). 

At the conclusion of the study, I plan to work with UNH Cooperative Extension to develop a fact sheet about microgreen production in a modified cold storage and present at several farmer conferences.

Learning Outcomes

3 Farmers reported changes in knowledge, attitudes, skills and/or awareness as a result of their participation
Key areas in which farmers reported changes in knowledge, attitude, skills and/or awareness:

I gained skills around growing microgreens in a controlled environment, a new experience for me; my farming experience to date has been limited to outdoor growing during the spring, summer, and fall. Working with my Technical Advisors, I also learned new methods of calculating an enterprise budget.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.