Horti-Facts Case Study: Prospect Farms

Case Study: Prospect Farms is producing hemp starter plants in Grodan rockwool for its own outdoor production as well as for local farmers looking to expand their crop offerings.

Case File Facts


Prospect Farms


Prospect, Maine


Industrial hemp and medical cannabis


Prospect Farms was founded in 2018 and is licensed to produce medical cannabis and industrial hemp. The company owns 253 acres of which 56 acres are used for outdoor hemp cultivation.

“Currently we are focused on developing the company’s infrastructure,” said Alexander Liebster, who is CEO and head of operations. “We are licensed to produce both medical cannabis and industrial hemp, but our primary focus is on hemp and hemp processing.”

Prospect Farms also operates a 2,100-square-foot greenhouse to produce cannabis for medical products.

“The medical cannabis is a continuation of what I have done for about 15 years related to cases of pediatric epilepsy and pediatric oncology that I want to maintain. I expect our focus going forward will be on industrial hemp. We will be growing a larger volume of hemp outdoors than indoor-grown medical cannabis.”

“We had a 98 percent success rate as far as viability once the plants [in Grodan AO plugs] were in the field. We have hemp plants in the field that are 5-6 feet tall grown directly from the AO plugs.”

– Alex Liebster, head of operations and CEO, Prospect Farms


In order to be able to have enough hemp transplants for its own outdoor production, Prospect Farms is building three 30- by 98-foot propagation greenhouses.

“In addition to the cultivation of hemp transplants for the 50+ acres of hemp that we are growing, we will also be producing transplants for other farmers interested in growing hemp,” Liebster said. “We are a fully vertically integrated facility. We also offer hemp processing and extraction, product manufacturing and distribution.

“We are really community centric and community focused. I saw this as an opportunity, particularly as the hemp industry grows to be able to assist small farms and small family-owned shops which are being pressured and pushed out of the industry especially by big pharma, tobacco and some of the other companies with big investors. I wanted to be well-funded and big enough in capacity so that we could function as a business, but additionally set ourselves up from an infrastructure standpoint that we could provide these services for other small farms so that they don’t need to build an extraction facility or food and beverage manufacturing facilities. This would not only be good for our own business, but would also help to strengthen our community. It would allow other groups to really focus on the plant cultivation and retail businesses for themselves.”

Liebster said his intention is not for Prospect Farms to become the biggest hemp producer in Maine.

“I want to work with our local dairy and potato farmers who are subject to the hardships of their own industries,” he said. “Try to give them an opportunity via our ability to provide them with hemp starter plants at the beginning and final product distribution towards completion of the season. We would also assist with preparation of the fields for planting including installation of drip irrigation and laying plastic mulch--all of the things necessary for successful harvests in our locale.”


Liebster chose Grodan AO rockwool plugs for the production of his hemp transplants.

“I have been using Grodan very successfully for about 15 years mostly with growing cannabis,” he said. “I have worked with other growing media, but Grodan rockwool has always been my go-to substrate.

“I’ve worked with Grodan in the past planting cannabis outside, but it was a larger 1½- by 1½-inch cube. The 1-by 1-inch Grodan AO plugs that we are using for hemp come 200 plugs to a sheet and fit in 1020 trays. This is a much higher volume per sheet than 72- or 96-cell sheets allowing us to greatly increase production capacity.

“We are transplanting hemp seedlings in the Grodan plugs directly into the field. We are separating the seedling plugs from the sheet and transplanting them with a water wheel transplanter. The rooted transplants establish quickly in the field.”

One of the production challenges Liebster faced this year was producing enough hemp transplants in a 2,100-square-foot greenhouse for outdoor production.

“I worked with Kyle Barnett at Hort Americas to use the Grodan AO plugs to produce 200,000 plugs in the greenhouse space available in order to meet our needs,” Liebster said. “With the 1- by 1-inch AO plugs I was able to grow larger plants in rockwool than I was able to grow previously. I was able to start with 200 plugs per sheet which greatly helped in my ability to get the numbers that I needed in the small space that I was confined to. What was amazing to me was the level of control I was able to maintain. I kept the hemp plants in those 1-inch cubes for well over 1½ months and was able to maintain plant health. We had a 98 percent success rate as far as viability once the plants were in the field. We have hemp plants in the field that are 5-6 feet tall grown directly from the AO plugs.”

Liebster said that for future hemp transplant crops he will be doing both seed and vegetative propagation.

“I would like to use Grodan as my medium to start the plants from micropropagation,” he said. “We are working with a relatively large volume of seeds so we will be able to identify the genetics that are more stable for that type of propagation. We will also have a breeding project to create the genetics more for our climate in regards to cold tolerance, faster finishing times since we have short growing seasons, and a need for disease resistance.

“We are focused on putting female plants into the field which we will be able to do with micropropagation. This will provide us with more certainty so that we don’t have to cull male plants out of the field after they have been planted.”


The primary reason that Liebster chose Grodan AO rockwool plugs to propagate hemp starter plants was his familiarity with using the substrate.

“The second reason for choosing Grodan is the overall control I have with rockwool as a growing substrate,” he said. “It is relatively inert from a nutrient perspective. I have control over the pH that we are starting with. I am going to be using Grodan to propagate both industrial hemp and medical cannabis transplants.”

For more: Prospect Farms, Alexander@prospectfarms.co.


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