Can You Grow Mushrooms in the Tropics?

Growing your own edible and medicinal mushrooms is something that can boggle the minds of even experienced horticulturalists. In the tropics, it may seem like an even more unlikely feat. Like growing apples in the jungle.

While there are challenges for mushroom cultivation in tropical climates, it’s not as hard as you might think. In fact, with proper techniques and some simple precautions, it can be just like growing mushrooms anywhere.

Mushrooms In Tropical Climates

If you have doubts about growing mushrooms in tropical climates, there’s good reasoning for that – especially in lowland tropical climates where there are high temperatures all year long.

While there are tons of fungal activity in tropical ecosystems, nutrient cycling sways in favor of other decomposers in the hot tropics. Bacteria and insect detritivores thrive here.

Mushroom forming fungi in the tropics take a sidestep. Their niche focuses mostly on the decomposition of large woody materials like tree trunks and thick branches. Polypores and other wood-rotters are capable of thriving here, albeit that their host trees break down at accelerated rates. Since leaf litter and soil organic matter are largely consumed by other organisms, you’ll rarely see mushrooms fruiting directly from the ground in tropical climates.

Thankfully, there are varieties of fungi that are well adapted to the tropics. Many cultivated fungi, edible and medicinal, are well suited to handle the climate and grow vigorously. With proper care and some precautions, it can actually be quite easy to grow mushrooms in the tropics.

Mushroom Cultivation 101

Mushrooms are the reproductive structures of filamentous fungi. These fungi are largely composed of white cobweb networking filaments called mycelium. Mycelium grows within organic substrates with the main function to decompose cellulose and lignin as an energy source.

Growing mushrooms can be done in different ways. The general process involves the following steps:

1. As a ‘seed’ you need mushroom mycelium of your choice in the form of spawn.
2. A suitable organic substrate (such as pasteurized straw) is inoculated with spawn.
3. An incubation period allows the mycelium to grow within the substrate.
4. Mushrooms begin to form primordia and fruit from the substrate.
5. After several flushes, the mycelium will weaken and begin to decompose.

While there are various ways to grow mushrooms, I’m going to give you two great options for beginners:

• The Bucket Method: This method resembles the most popular commercial production method. It involves growing your mushrooms in a five-gallon bucket full of pasteurized substrate.
• Inoculated Logs: Mushrooms can be directly grown on cut tree trunks and branches. This process is a bit slower but is more passive and natural than other methods. This technique can yield great results but needs to be done on suitable woods.

The Two Crucial Ingredients

The two most important materials used in mushroom cultivation are the mushroom spawn and the substrate.

• Spawn: Spawn is living mushroom mycelium that is used to inoculate a substrate. Spawn is usually grown on grains, like wheat or millet, but may also be grown on sawdust. Spawn should be sourced from qualified producers to ensure it’s vigorous and clean. Signs of contamination, like red or green growths, may result in an unsuccessful cultivation effort. While DIY production of spawn is possible, it is a much more difficult and involved process.

  

  

• Substrate: Substrate is organic material in which the fungal mycelium grows and nourishes itself. It is a food source but also a habitat for mycelium. This means it should have adequate nutrients and physical properties like moisture and pH. Substrates most often undergo a pasteurization or sterilization process. In the case of logs, they must be from a proper tree species 3-4 weeks after cutting.

  

Common Substrate Types:

• Straw
• Saw Dust
• Wood-Burning Pellets
• Manure
• Wood Chips
• Agricultural Waste
• Grains (for spawn)
• Logs

Other Common Substrates in Tropical Regions:

• Sugar Cane Bagasse
• Corn Stalks and Cob
• Lemon Grass
• Vetiver
• Dried King Grass
• Dried Cow Grass
• Cotton Seed Hull
• Cacao Peels
• Rice Straw
• Peanut Shells

Tropical Trees Suitable for Mushroom Cultivation:

Not all tropical tree species are going to be suitable for mushroom cultivation. Certain species in particular work better than others. One of the easiest ways to find this out is by identifying local trees that already produce large fleshy mushrooms, like native oyster mushrooms. Certain tropical trees in plant families like Fabaceae or genera like Ficustend to have suitable woods for mushroom cultivation. Trees most often used for mushroom cultivation in the tropics are:

• Gunpowder tree (Trema orientalis)
• Koa (Acacia Koa)
• Albizia (Falcataria moluccana)
• Ironwood (Casuarina equisetifolia)
• Eucalyptus (Eucalyptus grandis)
• Tropical Oaks (Quercus sp.)
• Tropical Figs (Ficus sp.)
• Guava and relatives (Psidium sp.)
• Mango (Mangifera indica)
• American Mahogany (Swietenia mahagoni)

Warm Weather Mushroom Species Suitable for Tropical Climates

The following species do well in hot weather. In some cases, there are specific ‘warm weather’ strains of specific species.

• Pink Oyster
• Golden Oyster
• Reishi
• Florida Oyster
• Blue Oyster
• Elm Oyster
• Wood Ear

The Bucket Method

This method is simple and efficient for small-scale cultivation. It involves cultivating the mushrooms within 5 gallon (20 liters) buckets which act as the recipient for the inoculated substrate. This method could be applied with other recipients such as plastic grow bags or recycled plastic bags. I like it because the buckets are completely recyclable.

Materials Needed:

• 1 bucket for pasteurization with no holes
• 1 bucket with holes for cultivation
• Substrate sufficient for filling bucket
• Micropore tape
• Large pot and stove for heating water
• 1-2 liters of spawn

1. Making your Bucket

Before anything else, you need to make the bucket that you will grow your mushrooms in. I recommend using a food-grade bucket with a nice fitting lid. You will need a drill to make 1/4” holes. You can use a sharpie or pen to mark where you will drill.

Drill six holes in a line along the top, middle, and bottom of the bucket for a total of 18 holes. Try to space them out as evenly as possible. Some growers choose to make holes at the bottom to permit draining, but as long as you make sure your substrate isn’t excessively wet, you will be fine.

2. Preparing and Pasteurizing your Substrate

Make sure your substrate is finely chopped and easy to handle. For straw, I chop it into 5 inch pieces using a machete and a large log as a chopping block. Alternatively, you can do it with a weedwhacker. If you are using grass or plant material make sure it has been completely dried in the sun and lost its green color almost completely.

Once your substrate is prepared you will need to pasteurize it. This removes harmful microorganisms and makes it a suitable habitat for your mushroom. I do this using hot water and a 5-gallon bucket.

I place my substrate within a mesh bag like the one oranges are sold in.  This is placed within the bucket and compacted as much as possible. Afterwards, I fill the bucket with freshly boiled water and place the lid on top. If your pot isn’t big enough you can do it in 2-3 successive boils.

Then I let the bucket sit for 2-3 hours. You can place blankets or a jacket on the bucket to help insulate the heat.

3. Drain your Substrate

Take your mesh bag filled with substrate out of the bucket and hang it to drain. It will have to drain for 3-4 hours until it is no longer dripping. When tightly squeezed your substrate should only drip a couple of drops of water. Have patience with this step and don’t jump the gun.

4. Prepare for Inoculation

While your substrate is draining there’s a couple of things you can do to prepare. First, make sure the bucket with holes is clean. Wash it with soap if necessary and disinfect it with 70% alcohol.

You will want to inoculate in a clean space with an easily cleaned surface. The most comfortable is a table with a smooth surface. For wooden tables, I place a clean plastic tablecloth or tarp over it. Disinfect this surface with alcohol. This procedure is best done outside in a clean, dirt-free, space.

5. Inoculation

Make sure to wash your hands and arms thoroughly with soap and water. Afterwards, disinfect your hands with alcohol. Have your bucket, substrate, and spawn ready.

If your spawn is grown in jars you will need to break them by hitting the jars against a surface. A folded piece of cardboard on a hard surface will do. Hit the jar against the cardboard until it breaks into small pieces.

Here comes the fun part. Take your bucket and place a small two-inch layer of substrate on the bottom. Afterwards, sprinkle some of the mushroom spawn evenly across the layer. Use your hands if necessary. Add another four to five inches of the substrate followed by more spawn. Compact the substrate/spawn as much as possible within your bucket. Your goal is to make layers of the substrate with spawn in between.

Remember you only need around 5-10% spawn. 100 grams of spawn is plenty for 1kg of substrate.

After your bucket is full you can place the lid on it and close the holes with micropore tape. Just put a small piece on each hole. With a marker, you should write the date and type of mushroom somewhere on the bucket.

6. Incubation

After the inoculation, your bucket will have to grow for around 3-4 weeks. Place it in a cool, moist, and relatively dark area. Finding the right microclimate is key for the mushrooms to grow vigorously. If you have issues with rodents and you are using bags, make sure your bags are safe. Mosquito nets, camping tents, and other semi-permeable materials can work great to keep out insect pests like fungus gnats.

7. Fruiting

After about four weeks your bucket should be ready to fruit. If you don’t see small mushrooms forming naturally you can remove a piece of micropore tape and mist the hole with water. Increased air and water will stimulate fruiting. You can fruit it into the same space, just make sure the space is the coolest temperature you can achieve, with humidity and heavy shade. In a dry tropical climate, you may need to make a modified fruiting environment to increase the humidity.

Growing Mushrooms on Logs

This method is straightforward and one of the oldest techniques for cultivating mushrooms. While it’s a much slower process it is less energy-intensive. If properly undertaken it requires no input after the initial inoculation.

Materials

• Sawdust spawn or dowels
• Logs from suitable tree species (around 6-10” in diameter, 2-4 ft long, and 3-6 weeks after cutting)
• Drill with 9mm bit
• Candle wax
• Pot and stove
• Brush

1. Prepare Log

Clean log of moss, lichens, or other epiphytes that may be living on the log.

2. Drill Holes

Drill 9mm holes every 5 inches across the entirety of the log.

3. Fill with Spawn

Take your sawdust spawn and begin filling the holes. You can do this by hand or you can use a log inoculation tool. This is a tube you can fill with spawn and use to easily dispense it into the holes.

4. Cover with Wax

Melt the wax with a double boiler or whatever method you prefer. You will then use your brush to paint a layer of wax above the inoculation points. This will protect the spawn from insects and other critters.

5. Incubate and Fruit

Keep your log in an as cool and moist microclimate as you can. This method usually takes six months before producing fruiting bodies. With softer woods and more inoculation points, the process may be quicker. Fruiting should occur naturally when conditions are right but you can also stimulate it by soaking the log in cold water overnight.

Common Problems Encountered in Tropical Climates

• Excessive Heat

High temperatures favor the growth of bacteria and other contaminants. It’s crucial to have your fungi growing in as cool conditions as you can create. This could simply be a cool and moist microclimate or a specially constructed area. Fruiting spaces not only require moisture and temperature control but also plenty of fresh air exchange.

• Insect and Animal Pests

Insects and animals can cause havoc on mushroom growth. Rodents will go after grain spawn while insects eat living mycelium. While you may not necessarily encounter issues, these can be avoided by using the proper netting. A simple mosquito net placed over a bucket will protect it from fungus gnats.

• Contamination
  

Tropical ecosystems are full of bacteria and fungi. Spores and propagules float in the air and cover surfaces. That’s why I recommend taking good precautions when conducting the inoculation process. Conduct it in a clean well-ventilated space away from molds or rotting woods.