How to


How to Grow Cannabis in Mapito

“What is Mapito?” was my initial thought after reading the title of this assignment. While working and writing for the cannabis industry for several years, I have heard some unusual lingo surrounding the plant. However, I had never heard of mapito or its influence in the cannabis industry – until today.

A quick search revealed the elusive mapito as an alternative substrate for indoor hydroponic systems using a mix of rock wool and polyurethane (PU) materials. I could feel my head cock in a sideways ‘Huh?’ posture when I read the polyurethane insert.

Pondering an image of varnish for wood decking, I was trying to wrap my head around the polyurethane concept. How in the world did someone come up with a horticulture substrate using polyurethane to grow marijuana?

Further research divulged many different formulations of polyurethane composites, including the finishing sealant I envisioned for the deck. The PU forms used in mapito, on the other hand, are foams typically used for insulation purposes shaved down into absorbent flakes. This concept was much easier to visualize.

I then began looking deeper into how to grow cannabis in mapito. While mapito is similar to other hydroponic grow mediums, its composite structure requires a few different tactics to promote healthy plant growth.

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What are the Advantages of Growing in Mapito?

Good Absorption and Drainage

Mapito combines PU flakes mixed with rock wool or stone wool, creating an appealing environment for plant root development. Rock wool is renowned for its good absorption capabilities, making it a popular substrate in hydro gardening systems.

Polyurethane flakes mixed with rock wool in mapito create a light grow medium offering good porosity and drainage. The airy environment encourages abundant oxygen availability, increasing nutrient uptake and water flow through the marijuana plant’s system.

Abundant Oxygenation for Nutrient Uptake

One of the advantages of any hydroponic growing system provides cannabis growers complete control over nutrient inputs at different plant growth stages. Similarly, the mapito medium offers this same essential enhancer with the bonus of greater oxygenation for nutrient absorption through the roots.

Nutrient molecules transport readily in ample oxygenated environments. When cannabis plants take in water and CO2 through photosynthesis, a strong oxygen presence encourages molecular distribution. As the plant releases excess water vapour and oxygen through transpiration, the light mapito substrate provides a solid structure for the recirculating gaseous exchanges.

Savings on Input Costs 

Because of the flaky polyurethane inputs, mapito is a cost-saving reusable substrate. Similar to clay pebbles, mapito is a clean, conventional growing medium. The flakes can be cleaned and reused for subsequent grows, saving the cost of new substrate inputs with every flip in the grow tent.

Additionally, due to the abundant availability of oxygen in mapito flakes, molecular bonding of nutrient compounds occurs quickly within the root zone. As absorption rates increase, the amount of nutrient supplementation decreases. Marijuana growers will save on nutrient costs when growing in mapito. 

Potted Plants are Easy to Move 

Similar to coco coir, mapito flakes used in single pots provide flexibility for growers. Moving plants for pruning, defoliation, and low-stress training purposes helps cannabis growers tend their crops easier. Compared to growing in rock wool cubes or slabs, transporting plants is not an option due to the risk of root breakage or damage. Mapito offers more flexibility in a grow room design.  

Fewer Pest Problems 

Due to the inert nature of mapito, pests tend to stay away from this unnatural environment. Unlike root aphids and fungus gnats harbouring in moist conditions in other substrates, mapito’s porous conditions are not an appealing atmosphere for pest and pathogen infestations.

Mapito used for growing cannabis
Mapito as an alternative substrate for indoor hydroponic systems using a mix of rock wool and polyurethane (PU) materials

Disadvantages of Mapito Substrates

No Buffering Capacity

Due to the inert components in the medium, there is no buffering mechanism for stabilizing pH levels. As with all things cannabis, pH balancing is essential for optimal plant growth. Similarly, electric conductivity (EC) in a soluble solution may fluctuate without a buffer.

While all mediums must be monitored for pH and EC levels when growing cannabis in hydroponic systems, inert materials require strict attention to detail to keep parameters within range.

Soak Mapito Before Planting  

Mapito must be soaked in water before use to increase water retention capacity. If the medium is not thoroughly drenched, it is unable to retain moisture efficiently. This effect can result in improper water and nutrient uptake throughout plant development.

The soaking also cleans mapito of any impurities such as excess salts or other chemical imbalances. A minimal 24-hour soak is recommended to thoroughly cleanse the substrate of any contaminants.

Best Practices for Growing Cannabis in Mapito

Easy DIY Soaking Instructions for Mapito

Fill a large bucket with enough water to submerge the mapito. It will absorb water readily, so keep liquid levels above the substrate. Check the pH and EC levels of the water before adding the mapito. This data gives a good base for additive requirements after the mapito is introduced to the water.

The pH will fluctuate during the substrate soaking period. A good rule of thumb is to stabilize the pH around 6.0 in the beginning. As the rock wool and polyurethane components become saturated, pH levels will stabilize.

Unfortunately, the pH may not fall in the ideal hydroponic parameters of 5.5 – 6.0 after the 24-hour soak. pH Up (potassium carbonate or potassium hydroxide) or pH Down (phosphoric acid) products are added to the bath to adjust pH levels accordingly.

Adjust EC levels between 0.3 – 0.4 during mapito soaking. If EC levels are high initially from the water source, distilled water or a reverse osmosis set-up may be required. Check the EC every couple of hours and record changes. Unfortunately, if the EC is above 0.4 after 12 – 15 hours, drain all water from the substrate and re-soak with fresh water.

Filling the Plant Pots

After stabilization at the above-recommended pH and EC levels, fill plant pots to the rim with the soaked mapito. The saturated medium will begin draining, subsequently settling into the new environment. Due to its composition, the growing media will seem light and airy even when drenched.

The substrate will shrink as it dries out, leaving a large void at the top if not filled adequately.

Apply light pressure to squeeze excess water out, although a natural drying process ensures the substrate will perform optimally. Mapito is resistant to compaction, allowing for expansive root growth with ample oxygen availability in the porous substrate.

Capture run-off from one or two pots and measure pH and EC. These early recordings establish a base to grow on.

 Growing a Cannabis Plant in Mapito

Whether starting a favourite cultivar from a tiny cannabis seed or encouraging rapid root growth from a fresh clone cutting, mapito provides a stable environment for early marijuana plant development. Maintaining pH and EC levels during the start of vegetative growth encourages the young plant to perform well.

As with all indoor hydroponic set-ups, the grower controls the system. If you want to flip a vibrant marijuana plant into the flowering stage a few weeks into veg, simply change the grow light cycle to 12-12. Mapito easily adapts to pH and EC incremental changes as the cannabis plant matures in growth development.

Growing in mapito for the first time is similar to other hydroponic substrates. However, due to the rock wool – polyurethane structure, abundant oxygen is pumped through the root system. The highly oxygenated substrate encourages both photosynthesis and transpiration.

When expedited water and nutrient fortification is available for plant uptake, canna plant growth excels to new heights. Dutch growers who first began experimenting with mapito boasted a ten-fold yield increase with accented flavour and potency effects.

Planning for a Mapito Grow

The cool thing about growing cannabis is – just when you think you’ve got the process figured out, something new comes along. Who would have imagined cannabis grown in polyurethane back in the early days? It just goes to show – you never know it all, especially when it comes to this divine plant species.

Post author
Charle Thibodeau
Charle’ Thibodeau is a freelance writer with almost a decade´s experience, specializing in cannabis content for the past two years. A strong motivation to educate, inform, and promote the culture surrounding this miraculous plant is her earnest mission.
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