Hemp mats, coconut coir mats, different thicknesses, and binding agents – which growing medium is best suited for microgreens?
Anyone who grows microgreens knows that choosing the right growing medium can make a significant difference. Water absorption, moisture distribution, root development, and interactions with nutrient solutions all influence the growing process.
In professional or automated microgreens production, it is particularly important that growing materials have consistent and reproducible properties.
That is why we are currently taking a closer look at different growing mats made from hemp and coconut fibres. In cooperation with the manufacturer ProFlora, we are preparing a comparative testing series to investigate different material thicknesses, fibre structures, and manufacturing methods.
Why Is Choosing the Right Growing Mat So Important?
Microgreens have a relatively short growing cycle. Within just a few days, seeds must germinate, develop roots, and absorb sufficient water.
The growing medium provides the foundation for uniform plant development.
A suitable growing mat should meet several important requirements:
- Uniform water absorption: Water should spread as evenly as possible throughout the mat.
- Good water retention: The fibres should retain sufficient moisture without remaining excessively saturated.
- Adequate oxygen availability: Roots need oxygen as well as water.
- Structural stability: The mat should maintain its shape throughout cultivation and harvesting.
- Low soluble salt content: Unwanted soluble salts should have minimal influence on nutrient availability.
- Consistent material quality: Thickness, density, and fibre structure should remain as uniform as possible between production batches.
Reproducibility is especially important in automated irrigation systems. If different mats behave differently, precise control of water delivery becomes significantly more difficult.
Hemp Growing Mats for Microgreens – Natural and Versatile
Hemp is an interesting raw material for producing growing mats.
Its natural fibres can be processed into mats with different thicknesses and structural properties.
For our planned experiments, we are particularly interested in hemp mats with thicknesses of 5 mm, 8 mm, and 10 mm.
How Does Mat Thickness Affect Growing Performance?
The thickness of a growing mat can influence several characteristics.
Thinner mats require less material and may be particularly suitable for short growing cycles with frequent irrigation.
Thicker mats potentially provide more space for water storage and root development. However, actual water retention depends not only on thickness but also on fibre density, pore structure, and manufacturing processes.
Therefore, it is not possible to conclude that a 10 mm mat is necessarily better than a 5 mm mat.
What matters is how each material performs under real growing conditions.
Coconut Coir Mats – An Interesting Alternative
Alongside hemp, coconut fibres are another plant-based material that can be used for microgreens cultivation.
Coconut coir is obtained from the outer husk of coconuts. Its properties vary depending on fibre content, processing methods, and pretreatment.
Two different versions are particularly interesting for our experiments.
1. Coconut coir mats without binders
These mats are manufactured without an additional binding layer.
This is especially interesting when the goal is to introduce as few additional substances as possible into the growing system.
2. Coconut coir mats with a one-sided binder
In this version, one side of the mat is reinforced with a binding layer.
This could provide advantages in handling, transportation, and mechanical processing.
Whether the binding layer also affects water absorption, root penetration, or drying behaviour will be investigated during practical testing.
Electrical Conductivity (EC) and Salt Content – An Often Overlooked Factor
One particularly important characteristic of coconut-based growing media is their content of water-soluble salts.
Depending on their origin and processing, coconut materials may contain varying amounts of potassium, sodium, chloride, and other soluble ions.
These substances influence the electrical conductivity (EC) of a water extract.
Why Is EC Important?
Electrical conductivity provides an indication of the total concentration of dissolved, electrically conductive substances in a solution.
If a growing mat already contains soluble salts, these may be released into the irrigation or nutrient solution during watering.
This becomes especially relevant when using precisely formulated nutrient solutions.
However, a high EC value does not automatically mean that a substrate is unsuitable. The actual ionic composition, crop species, and nutrient solution must also be considered.
What Does the Manufacturer Say?
During our discussions with ProFlora, the manufacturer explained that particular attention is paid to salt content during the production of its coconut fibre mats.
According to the manufacturer, elevated EC levels in coconut materials are often associated with the finer components of coconut husks, particularly cocopeat.
Coarser coconut fibres are expected to behave more favourably in this respect.
This is an interesting observation. Nevertheless, coconut fibres themselves may also contain soluble salts or participate in ion exchange.
For this reason, we intend to evaluate the actual properties of the materials through our own measurements.
OEKO-TEX STANDARD 100 – What Does the Certification Mean?
Another interesting aspect is material testing and quality control.
According to ProFlora, its coconut fibre mats are certified according to OEKO-TEX STANDARD 100.
This standard includes testing for various potentially harmful substances in textiles and textile-related materials.
For the evaluation of growing media, such certification can represent an additional quality consideration.
However, an important distinction must be made.
OEKO-TEX STANDARD 100 certification does not automatically mean that a material is approved for direct food contact or specifically certified for use as a horticultural growing substrate.
For professional applications, the specific certificate, its scope, and any additional relevant material documentation should therefore be reviewed.
Our Planned Practical Comparison: Hemp vs. Coconut Coir
To compare the different materials objectively, we are planning a series of tests involving several growing mat variants.
| Growing medium | Variant | Main testing focus |
|---|---|---|
| Hemp fibre mat | 5 mm | Water absorption and root penetration |
| Hemp fibre mat | 8 mm | Moisture distribution and stability |
| Hemp fibre mat | 10 mm | Water retention and root space |
| Coconut coir mat | Binder-free | Fibre structure and water behaviour |
| Coconut coir mat | One-sided binder | Stability and influence of the binding layer |
The hemp thicknesses listed above are the requested test variants; their final availability has not yet been confirmed.
Which Properties Will Be Investigated?
Water absorption and water retention
First, we want to determine how much water the dry mats absorb and how much moisture remains after a defined drainage period.
EC and pH measurements
Using standardised water extracts, we aim to investigate whether the materials release measurable amounts of soluble substances and how they influence the pH of the extract.
Water distribution
We want to understand whether moisture spreads evenly throughout each mat or whether certain areas dry out more quickly than others.
Root development
Practical cultivation trials will help us observe how different microgreens species develop on the various materials.
Mechanical stability
We will also examine whether the mats maintain their structure after repeated irrigation, lifting, handling, and harvesting.
Why Comparable Testing Conditions Matter
A meaningful comparison requires testing conditions that are as consistent as possible.
These include:
- The same seed batch and sowing density
- Identical growing trays
- Consistent irrigation volumes
- Comparable lighting and temperature conditions
- The same growing period
- Standardised EC and pH measurement procedures
The measurement method is particularly important when determining EC.
The ratio of material to water, extraction time, and quality of the water used can significantly influence the results.
Only when these parameters are documented can the measurements be compared meaningfully.
Which Growing Mat Is Better – Hemp or Coconut Coir?
There is currently no universal answer.
Both materials have interesting characteristics that may perform differently depending on the cultivation method.
Hemp mats may offer advantages through their fibre structure and the availability of different material thicknesses.
Coconut coir mats also have promising properties, although processing methods, salt content, and potential binding agents deserve closer investigation.
Ultimately, the best choice depends on several factors: the microgreens species being grown, the irrigation system, the desired growing period, and practical handling requirements.
Conclusion: The Best Growing Mat Must Prove Itself in Practice
Choosing the right growing medium should not be based solely on the raw material or product description.
For reliable microgreens production, measurable properties and practical growing experience are essential.
Our exchange with ProFlora provides an opportunity to explore different hemp and coconut fibre mats and compare their performance systematically.
We are particularly interested in understanding how material thickness, fibre structure, and binding agents influence water absorption, EC, and root development.
Our goal is not simply to discover which growing mat works well, but to understand why it works.
What’s Next?
Once the material samples arrive, we will begin our first comparative measurements and cultivation trials.
We will publish the results here on microgreen-matten.de, including measurement data, photographs, and practical observations.
Step by step, this will help build a more evidence-based foundation for selecting suitable growing mats for microgreens production.
Note: This article describes the preparation of an independent material evaluation. The products mentioned have not yet undergone final testing. Statements provided by the manufacturer are identified accordingly.