Hemp hurd fiber: a sustainable substitute for sphagnum peat moss in greenhouse and nursery plant production

Progress report for LNE23-477R

Project Type: Research Only
Funds awarded in 2023: $161,414.00
Projected End Date: 02/28/2026
Grant Recipient: University of Connecticut
Region: Northeast
State: Connecticut
Project Leader:
Dr. Jessica Lubell-Brand
University of Connecticut
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Project Information


Sphagnum peat moss is an important component of greenhouse and nursery plant potting media, but mining of the material is unsustainable due to its negative environmental impacts. Several European countries have banned the sale of peat to consumers, and restrictions are likely to be extended to the horticultural industry. Restrictions on the sale of peat are expected to expand to Canada, which is the major supplier of peat to the United States. Hurd is a byproduct of all hemp growing operations (fiber, grain, medicinal) and is an untapped renewable material. Milled hurd is similar to peat in many characteristics (porosity and water-holding capacity) and can likely serve as a substitute in container media. The novel approach is to repurpose hemp hurd fiber as a substitute for peat moss in container growing media for the production of horticultural crops. Research is needed to ascertain the amount of hurd that may be substituted for peat, what crop groups may be grown using hurd, and the impact hurd will have on nutrient availability. Outdoor nursery and indoor greenhouse production studies will be conducted to evaluate if hemp hurd can be used to fully or partially (33% or 66%) replace peat in growing media for crops of woody plants (evergreen and deciduous), herbaceous perennials and ornamental grasses, bedding plants, and vegetables. The availability of nutrients in hurd substituted media compared to peat-based media will be evaluated. The horticultural industries recognize that regulation of peat is on the horizon and alternatives must be identified that make their crop production more sustainable. In a recent survey of southern New England growers, 100% responded that they were extremely or strongly interested in research evaluating sustainable alternatives to peat in growing media. All growers surveyed agreed that the use of hemp hurd, a renewable resource, for plant production would be viewed favorably by the public. As part of the process of fully evaluating hurd as an alternative to peat, a nursery producer will grow plants on farm using hurd substituted media. Growers will participate in annual on-site demonstration events where they will view the outdoor nursery and greenhouse trials, receive preliminary research results, and provide feedback on the project.  To reach a broader stakeholder audience, short educational videos that serve as “Reports from the Field” will be developed to highlight research activities and results and shared via UConn Extension, advisory committee member, and grower social media accounts.

Project Objective:

Evaluate hemp hurd as a substitute for sphagnum peat moss in growing media for container production of horticultural crops. Knowledge will be acquired about what crop groups may be grown using hurd, the amounts of hurd that may be combined with traditional media components, and the impact hurd substitution has on the availability of nutrients. If it can be shown that hurd may be successfully substituted for peat during production of horticultural crops, then growers will seek to use this byproduct of the hemp industries.


Peat is an important component of greenhouse and nursery plant potting media, but mining of the material is unsustainable due to its negative environmental impacts including emission of carbon dioxide, the major greenhouse gas driving climate change. The damage caused by peat mining has prompted several European nations including the United Kingdom, to enact bans on the sale of peat to gardening consumers beginning in 2024 (Carrington, 2021). Climate scientists and conservationists are calling on governments to place limitations on the use of peat by the horticulture industry. In discussions with representatives from horticultural product supply companies, it was shared that similar restrictions on the sale of peat will be enacted in Canada in the near future. Peat bans will significantly impact greenhouse and nursery container growing operations in the United States (US), since nearly all of the peat sold in the US comes from the peat bogs of Canada (Higgins, 2017). Hemp produces two types of stem fibers. The first is high quality long fibers (bast) that are used for textiles and the second is shorter more lignified fibers (hurd), which has few identified uses. Only 3.5% of the hemp stem consists of bast, which means that 96.5% of a hemp fiber crop is hurd byproduct. Hurd is a byproduct of all hemp growing operations (fiber, grain, medicinal) and is an untapped renewable material. Milled hurd is similar to peat in many characteristics (porosity, water-holding capacity, bulk density) and can be expected to serve as a substitute in container media. Hurd will likely resist breakdown and provide structure for longer than other components, which is desirable for container production. Greenhouse and Nursery Products are the number one agricultural commodity in five (Connecticut, Massachusetts, New Hampshire, New Jersey, and Rhode Island) of the 12 Northeast SARE states (Census of Horticultural Specialties, 2019). It is number two in Maryland and New York and number three in Maine, Pennsylvania, and Vermont. In Connecticut, Greenhouse and Nursery Products contribute 51% of the value of agricultural production, with Dairy a distant second at 14%. There are 2,452 wholesale operations in the 12 Northeast SARE states that produce bedding plants, herbaceous perennials and/or woody ornamentals. The majority are family or individual owned and range from 50 to 500 acres. A 500-acre outdoor container production nursery utilizes approximately 17,500 cubic yards of peat annually. The nursery industry recognizes that alternatives to peat must be developed and is interested in new products that make their crop production more sustainable (Jackson, 2022). The demand for alternative media components has never been higher and will only increase exponentially in the future. Many parts of the hemp industry are expanding rapidly and there will be significant amounts of hurd produced directly from fiber production or as a byproduct of grain and flower production. Developing end product and markets for the hurd material now will prove helpful to hemp farmers as well as greenhouse and nursery growers in the future.


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The research objective is to ascertain if hemp hurd fiber can be used to fully or partially (at 33% or 66%) replace sphagnum peat moss in container potting media and how broadly it can be applied to different crop groups including annual bedding plants, vegetables, herbaceous perennials and woody ornamentals. The degree to which the hemp substitute effects the availability of nutrients compared to peat will be determined.

Materials and methods:

2023 Greenhouse studies


The experiments conducted in 2023 were part of proposed study 3, which involved bedding plants. Experiments were conducted in the greenhouse at the UConn Floriculture Greenhouse Facility in Storrs, CT. Both experiments were conducted with petunia started from seed (Petunia Spreading, Shock Wave Series). There were four different treatment medias in both experiments: the control media consisted of 1:1 peat: vermiculite, which is representative of media typically used to grow greenhouse crops. The three other treatment media were as follows: 1:1 peat: vermiculite; 0.66:0.33:1 hurd: peat: vermiculite; 0.33:0.66:1 hurd; and 1:1 hurd: vermiculite. In experiment 1, the hurd product had a particle size of 8 to 10 mm (Biocomposites Inc.) and the vermiculite used was medium grade for texture. In experiment 2, the hurd product had a particle size of 2 mm (Hemp Trader Inc.) and the vermiculite used was fine grade for texture.


For each experiment, the experimental unit was an individual potted plant. Experimental units were arranged in a randomized complete block design with 10 replications. Three week old seedlings were potted into 6.5-inch azalea containers and top-dressed with 3 g (the manufacturer’s recommended low rate) of controlled release fertilizer (15-9-12 Osmocote Plus 3 to 4-month formulation). Plants were grown and evaluated for six weeks.

Data Collection

The porosity and water-holding capacity of each treatment media was determined. Pour thru (PT) testing was conducted weekly and the pH and electrical conductivity of the leachate was measured. Plant canopy width (the average of two perpendicular widths) was recorded weekly. Data was collected on the number of days until first open flower, the number of open flowers and flower buds at 21 days after potting and at harvest, and the above media fresh weight at harvest.

Data analysis and presentation of results

Data analysis is being conducted.

Research results and discussion:

2023 Greenhouse Studies

The hurd product from Biocomposites had a higher pH of 7.0 then was expected. The Biocomposites product required washing prior to mixing treatment medium to remove debris. The product was also contaminated with hemp seed that sprouted in the first 1 to 4 days after potting. Hemp seedlings were easily removed by hand. Based on visual observations of the first petunia experiment it was determined that the particle sizes of the Biocomposites hurd (8 to 10 mm) and the medium grade vermiculite were too large, making the treatment medium too porous. For the second petunia experiment we used fine grade vermiculite (with smalle rparticle size) and a different hurd product by Hemp Traders with particle size of 2 mm, that more closely resembled the particle size and texture of sphagnum peat moss. The Hemp Traders product had a lower pH of 5.0 and was free of debris and seed. Petunias in all hurd treatment mediums grew better in the second experiment than the first experiment based on visual observations. Future experiments will utilize the Hemp Traders hurd product at 2mm particle size.

Figure 1. Peat and hurd substrates.


The tables below provide the physical properties of the four treatment mediums in experiment 1 (Table 1) that used ~10 mm sized hurd and experiment 2 (Table 2) that used ~2 mm sized hurd.

Table 1.

Treatment Effective water holding capacity (% volume) Container capacity (% volume) Air-filled porosity at EWHC (% volume) Air-filled porosity at CCAP Bulk density (g/cm3)
Control 33.57 55.91 42.02 19.68 0.16
1H:1V 34.9 40.9 47.28 41.27 0.03
33H:66P:1V 38.65 54.09 41.66 26.21 0.02
66H:33P:1V 39.91 48.12 42.75 34.54 0.02

Table 2.

Treatment Effective water holding capacity (% volume) Container capacity (% volume) Air-filled porosity at EWHC (% volume) Air-filled porosity at CCAP (% volume) Bulk density Final, at EWHC (g/cm3)
1P:1V (Control) 48.93 65.98 28.2 11.14 0.65
1H:1V 48.38 60.05 35.37 14.7 0.63
33H:66P:1V 49.13 68.23 30.38 11.29 0.65
66H:33P:1V 50.76 68.29 28.46 10.92 0.65


The figures below shows petunia plants grown in 1:1 peat: vermiculite; 0.66:0.33:1 hurd: peat: vermiculite; 0.33:0.66:1 hurd; and 1:1 hurd: vermiculite (left to right) for experiment 1 using ~10 mm hurd (top) and experiment 2 using ~2 mm hurd (bottom).

Figure 2A

FIgure 2B

Participation Summary

Education & Outreach Activities and Participation Summary

Educational activities:

1 Webinars / talks / presentations
1 Other educational activities

Participation Summary:

10 Farmers participated
4 Number of agricultural educator or service providers reached through education and outreach activities
Outreach description:

1. Annual meeting about this NESARE project which included UConn extension educators and growers.

2. Presentation titled "Multipurpose Hemp: Cultivars and Breeding" at the UConn Extension event titled "Hemp Justice: Building a Circular Economy in CT".

3. Extension video "Report from the Field" about media mixing, pour thru testing, data collection and plant harvest of petunias.

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.