5 "Grow-Your-Own" Mulch Plants for the Tropics

Guest post by Scott Gallant

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The tropical forest is constantly self-mulching. After a walk in the woods I usually return with bits of leaves and twigs caught in my hair. Lying in bed at night, my partner and I often hear branches and even whole trees tumbling toward the great soil food web below. This self-mulching is one important piece in the self-renewing fertility cycle of the tropical forest. And of all the functions of the forest that we can seek to mimic, generating and applying our own mulch may be the most important.

Mulch has many familiar functions, like reducing soil temperature and maintaining higher moisture levels.  But all of these means really flow toward one perfect end: feeding and housing the microbial soil community. It is this community that runs the engine which results in a healthy, happy, and abundant permaculture farm.

Grow Your Own Mulch

With this in mind I've spent years seeking out the best means for mulching our food forest. In the early days this involved traveling to neighbors' farms and loading the truck with banana trunks and rice straw. Unfortunately in rural Costa Rica, unlike many parts of the temperate world, there are not huge quantities of organic material lying around as waste, ready to be re-appropriated. Organic material, my future mulch, doesn't sit around waiting for the right farmer to scoop it up--here, the tropical rain and sun break it down rapidly. And local farmers generally re-purpose most waste products before they become, well, waste.  We quickly found we had to find another solution for acquiring mulch.  We decided to grow our own.

We began planting thousands of nitrogen fixing trees (NFTs) that could be chopped and dropped in place for mulch. This has worked great in general, but I've found that other plants not in the legume family actually far out produce most of these trees when it comes to biomass. I've come to believe that there is an over-emphasis on NFTs in the tropical permaculture community, and instead we should focus more on the biomass quantity itself. While I wish all of my mulch was rich in nitrogen, what I'm now seeking is weed suppression and moisture retention. Both of which take a hard stab at eliminating my least favorite activities, weeding and watering; all while moving us closer to the no-work permaculture ideal.

Top 5 Mulch Plants

For our climate, the low land humid tropics, these five plants are what I recommend to clients for growing prodigious amounts of mulch.

Cuadrado/Guineo (Musa sp)

A species sharing the same genus as bananas and plantains, cuadrados are generally considered a less domesticated crop. They grow rapidly, spread aggressively, propagate easily, and produce a delicious fruit that can be used in nearly the same way as plantains. In our corner of the world, they are considered a poor person's food, likely because they produced when nothing else did.

The trunks can be cut back multiple times per year and they will keep sprouting out of the same base. The leaves are slow to decompose, like many plants on this list, and provide excellent weed suppression.

In addition they are a great pioneer species; creating a shady microclimate for your more delicate climax species.

Torch Ginger (Etlingera elatior)

This huge ornamental ginger is a fixture in tropical gardens around the globe for its beautiful flower, huge leaves, and the dense shade they produce. It takes two years for this plant to take off, but once it does you have a steady diet of 4 meter long herbaceous stems and leaves ready for chop and drop mulch.

Torch ginger propagates by root division. One plant can be scaled easily into many more. It works well as a privacy barrier between lots or between public and private spaces. Don't chop it completely to the ground but consistently remove older stems with a clean cut near the base of the plant.

Vetiver (Vetiveria zizaniodes)

Vetiver grass, already in the tropical permaculture lexicon for its use as an erosion control species, is also a great multi-functional mulch plant. It is a bunching grass, with a deep root system. It doesn't produce seeds and thrives in full sun on recently disturbed sites. Where it gets plenty of water and sun, the grass will grow to reach two meters in height.

It can be cut back to 30 cm two to three times per year. The mulch is dense and slow to break down. Use a nice set of hedge shears, a sharp machete, or a weed trimmer with a metal blade attachment for cutting vetiver. Use gloves as the grass can easily cut an exposed hand running along the edge.

It is propagated easily by root division. Keep young plants free of weed competition for two years and they will reward you with prolific growth and biomass.

Mexican Sunflower (Tithonia diversifolia)

This wild sunflower, also known as Boton de Oro, is a woody shrub reaching up to 4 meters in height. It is gaining traction in the tropical agroforestry community for its use in silvopastoral systems and as a green manure. It makes a great cut and carry fodder for cattle and goats throughout the dry season.

The Mexican sunflower easily propagates by cuttings and loves full sun, where it throws out a beautiful flower throughout the dry season that support a host of pollinators. It purportedly, like sunflowers, has the ability to accumulate phosphorous in its leaves and stems. This would be a nice addition to any mulch pile. Hack at the plant with a machete or clippers with little fear or taking too much off. It has a strong coppice response, providing a steady supply of woody mulch.

More research is needed on this support species, as it appears to be an important addition to our agroforestry plant matrix.

Bijagua (Calathea lutea/crotalifera)

This large herb reaches nearly 3 meters tall and has 1 meter long leaves. It loves wet, marshy sites, where it can quickly take over if not managed. It is common along the road side of the lowland tropics throughout Central America.

Bijagua produces a massive quantity of leaves throughout the year, which have a waxy coating that slows their decomposition, making them ideal for weed suppression. Their flowers are great for hummingbirds and other pollinators, and the leaves have historically been used for thatch roofs, to wrap tamales, and of course as quick umbrellas.

They do produce seeds, which are dispersed by birds, but are mostly propagated by root division. You can chop them down to the base completely and they will shoot back new leaves in record time.

Patterns for Mulch Species

There are a number of patterns worth recognizing that nearly all of these plants complete:

• They are propagated easily by division or cutting.
• They have large, slow to decompose leaves that keep the soil covered longer.
• They don't produce seed, so they have a very low invasive potential.
• They grow quickly, acting as pioneer species, and changing the microclimate around them.
• They are easy to chop because they are herbaceous.
• They hold their leaves throughout the dry season which help shade the soil during the hottest months of the year.

As you look for mulch and biomass plants in your own climate, look back at these patterns as guides. They might lead you to the next ah-ha moment and jump start the success on your site.

To see these plants in action come visit us at Rancho Mastatal Sustainability Education Center or reach out to the design team at http://ranchomastatal.com/ for advice on growing your own mulch.

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Scott Gallant is an agroforester and food system designer with nearly a decade of experience working in Central America. He is the co-founder of Porvenir Design, a landscape design firm specializing in building soil and growing food. As the farm manager at Rancho Mastatal Sustainability Education Center he works with an amazing team to cultivate 15 acres of an emerging tropical agroforest. He can be reached at scottgallant@porvenirdesign.com.