Table of Contents
The General Principle - How to Think About Plant Care.
On Replicating the Light - Envision the Rainforest Canopy.
On Replicating the Rain - Weighing the Effects of the Hydrologic Cycle.
On Replicating the Soils - Structure, Fertility, and Microorganisms.
The Quick Reference
The General Principle - How to Think About Plant Care.
The best way to learn about a new tropical plant’s care needs is to first understand the plant’s native habitat. Wherever on earth that plant comes from… to understand the conditions in which your tropical plant naturally thrives is to take a huge step forward in providing it the best care possible, whether you’re familiar with the plant or not.
The Alocasia above (or at least its lineage) grows naturally in the rainforests of southeast Asia and northeastern Australia.
The Tradescantia below is native to Central and I believe South America but has been introduced into the same south Asian rainforests that the Alocasia calls home. Introduced. Hold on to that for a minute.
The question, of course, is: How do I know where my plant came from?
Here’s where it gets easy. Whether the plant is an Alocasia from Borneo, a Monstera from Panama, or a Philodendron from southern Florida, the fundamentals of the environment are the same country to country and continent to continent. The tropics are the tropics. And a rainforest is a rainforest is a rainforest.
How do I take care of my tropical plant? Replicate the basic properties of the plant’s native habitat.
Q - And if I don’t know where it comes from?
A - Doesn’t much matter. Replicate the properties of a rainforest.
The reason the Tradescantia now thrives in rainforests which aren’t its native home; the reason its introduction to foreign forests was successful is due to the fundamental properties of the tropical rainforests of Central America and those of southeast Asia being essentially the same. A rainforest is a rainforest is a rainforest.
The best way to take care of your plant is to replicate the properties of its native habitat.
On Replicating the Light - Envision the Rainforest Canopy.
The big statement from my last post about the care of tropical plants was this: the best way to care for a plant is to replicate the basic properties of the plant’s native habitat. And then the transition into today’s topic: Whether the plant is an Alocasia from Borneo, a Monstera from Panama, or a Philodendron from southern Florida, the fundamental properties of the rainforest environment are the same country to country and continent to continent. The tropics are the tropics. And a rainforest is a rainforest is a rainforest.
It's not necessary to know anything about Borneo, or Brazil, or Malaysia or whichever specific geographical location your plant calls home. The rainforested areas of the tropics offer the same basic environmental properties regardless of the country.
So, what are these properties?
Today, we’ll consider the sunlight that a tropical plant would typically receive in its native habitat.
Picture the rainforest. Begin with the canopy of the trees. Above the canopy, for much of the year, you see rainclouds, so the sun isn’t often as bright as you might expect. In the higher layers of the canopy, itself, you see varying degrees of direct and indirect light as the branches and foliage shade and reflect. As we descend lower into the canopy, the light is filtered by 60-70%. And by the time the sunlight hits the forest floor it is reduced by about 98% (this is why so many tropical plants are either epiphytic (grow in the branches of other trees) or climbing/vining – they are trying to get more light than the 2% available on the forest floor).
Since the vast majority of the tropical plants that you and I may grow in our homes are still considered understory plants – found growing beneath the canopy of larger trees – we know that the light they’d receive in nature is heavily filtered and mostly indirect.
So, how do we replicate this property in our homes? It’s really just a matter of knowing the amount of light that our windows receive.
A south-facing window is usually going to provide the most intense, direct light for the most hours throughout the day. While this might be best for desert plants, without significant filtering (maybe a tree shades that window to some degree?) a south-facing window will usually provide too much light for tropical plants.
A west-facing window is often the same as the south – too much light. If these are the only options you have, however, it’s just a matter of observing which areas of the room do not get that direct light from the window and placing the plant in that area.
A north-facing window will receive the least amount of light but may receive enough indirect
light to offer a good placement, particularly if the plant can be situated fairly close to the window.
In most cases, an east-facing window is going to provide the best light for tropical plants. The morning sun is less intense and the duration of light is shorter.
Beyond all of the thoughts of which window faces which direction, however, the focus should be on achieving a lighting plan which best replicates the light that a tropical plant would receive in its native habitat – heavily filtered and primarily indirect.
In our tropical house in Bonne Terre, we have a couple of different strategies for achieving the right amount of light. Throughout the cooler seasons, when the days are shorter and the sun is lower in the sky, we cover the greenhouse roof with 40% shadecloth. This allows 60% of the sunlight in, but it’s obviously quite filtered. There is also significant indirect light available which bounces off the white sidewalls.
When the sun is higher in the sky through the warmer months, we add a floating shadecloth to a portion of the greenhouse which filters about 70-80% of the sunlight . So, through the summer months, for example, our tropical plants will receive a few hours of slightly filtered morning sun before the sun is high enough for our shadecloths to be effective, followed by several hours of mostly indirect light.
What I hope to communicate through these posts, in general, is that the complexity of growing various plant species is often overblown. In most cases, success comes simply by knowing the general properties of the plant’s native habitat – a rainforest, in this case – and then replicating those properties in our homes.
More specifically, I want to communicate that to grow one tropical plant is akin to growing them all. This is not to say that there are no variables to consider when growing one tropical plant versus another, but that the variables are so insignificant – a tiny bit less light or a tiny bit more humidity, for example – that as long as replicating the basic growing conditions of a tropical rainforest is the focus, the process of growing the plant will be much simpler.
On Replicating the Rain - Weighing the Effects of the Hydrologic Cycle.
The general theme I’m working with through this tropical plant care series is this: The best way to learn how to care for any plant is to learn about that plant’s native habitat and then replicate those conditions at home.
But what if I have no idea where my plant comes from?
The sub theme of this series is essentially this: It’s not necessary to know anything about Borneo, or Brazil, or Malaysia or whichever specific geographical location your plant calls home. The rainforested areas of the tropics offer the same basic environmental properties regardless of the country. A tropical rainforest is a tropical rainforest, and the basic environmental properties of rainforests are the same throughout that entire central global belt that we call the tropics. Now you're caught up.
Learn the properties of the rainforest and you’ve essentially learned to care for tropical plants. Any of them.
One of the most obvious properties of the rainforest is… wait for it… the rain. But though I’ve titled this post Replicating the Rain (the title just sounds cool), to better understand our plants we have to broaden the scope to touch on the hydrologic cycle, in general: evaporation, transpiration, condensation, precipitation, runoff – but we’ll begin with the rain. It is, without a doubt, the elephant in the room.
Some annual rainfall stats to set the stage:
In Missouri, we receive about 45 inches of rainfall per year. Compare this to the rainforested regions of Panama, in Central America, which receive closer to 480 inches. Missouri, about 4 feet of rain. Panama, about 40 feet. Granted, this is on the extreme side of precipitation falling on the world’s rainforests but Panama is not alone. Parts of India – Mawsynram, for example, receive an averagre 472 inches per year. Cameroon, in Central Africa, gets about 400 inches.
Columbia – 140 inches.
Malaysia – 78 inches per year.
Borneo – 157 inches.
North Queensland Australia – 312 inches.
The general picture of precipitation in the rainforests of the world shows a level of moisture that is far beyond that which we’re accustomed to in Missouri. 4 feet versus 40 feet is hard to even comprehend but there are a few variables that should be kept in mind as we think about replicating the rain – terrain, competition, and all that remains.
The terrain of the world’s rainforests: Panama: mountains. Malaysia: mountains. Cameroon:
mountains. Borneo: mountains. 40 feet of water falling on mountainous terrain is going to disperse much more quickly than it would if it fell on a cornfield in Missouri. This is important to keep in mind because though there is so much rainfall in these areas, it rarely results in situations where tropical plants remain in soggy conditions. This is one of the key environmental properties that we need to replicate as we grow these plants at home.
Another factor to keep in mind involves the competition for resources – water, in this case – that is ever-present in the world’s rainforests. If you go back to picturing the flora of the rainforest, you’ll see endless and dense canopy and a few levels of understory plants beneath it – life so dense that sunlight barely gets through. Then, understanding that a single, mature tree can drink ten thousand or so gallons of water per year, multiplied by the plant density described, assures us that standing water in a rainforest is a resource that does not stand for long. There are bogs and wetlands, of course, but most of the tropical plants thet you’ll find in trade are not from these areas.
The last factor that should inform our tropical plant growing practices in relation to water involves all that remains of the hydrologic cycle. There is rainfall, there is run-off, there is plant uptake, and there is all the rest: evaporation, condensation, and transpiration. These last three, in sum, keep the bark and the leaves of trees moist. They keep soils moist. They keep mosses and debris damp. And they keep the air heavy. Whether it’s raining or not, the volume of water that cycles in tropical rainforests lends itself to very humid and damp conditions throughout the year.
So how, precisely, does all of this inform our growing practices at home?
Whether the plant is terrestrial (growing in the ground) or epiphytic (growing in trees) the roots of the plant have near constant access to moisture. Orchids, for example, growing epiphytically in the branches of trees, are sustained by the moisture that is held in the crevices of the tree bark, in the mosses that also grow in the trees, and by the continual evaporation of water from below. There is consistent moisture, but the plant is never in soggy conditions. And it’s the same with terrestrial plants. The terrain drains much of the water and competition drinks endless thousands of gallons, but the volume of water in the forests is always plenty for the philodendron to have constant access to moisture without remaining in soggy conditions.
When it comes to watering tropical plants, then, we replicate the properties of the plant’s native habitat by 1) assuring that the potting media we use drains well but doesn’t dry completely between waterings - keep the tips of their toes moist at all times (using an inexpensive moisture allows you to determine the moisture level at the bottom of the pot - nearly all tropicals should dry to a 2 or 3 on the meter before giving them a thorough drink), and 2) keeping the humidity level in their growing space high - the use of a pebble tray and occasional foliage misting and/or adding a small humidifier to the space can be very helpful in replicating the plant's experience with moisture in its native habitat.
A note on water quality: Tropical plants are more sensitive to the litany of chemicals and minerals found in the drinking water of most municipalities than very nearly any other grouping of plants. Filtered water may be a solution in some cases, but distilled or reverse-osmosis water is a better starting point. I’ll write more about this in the next post having to do with soils and fertility.
On Replicating the Soils - Structure, Fertility, and Microorganisms.
A good way to begin thinking about how the potting blend you choose for your tropical plant may affect the vigor of the plant is to first have a general understanding of the soil profile in which the plant would be growing in its native habitat.
But how on earth would one discover such a thing?
For those of you who have skipped to this section from the top, I'll just copy a line or two from above to catch you up.
"It’s not necessary to know anything about Borneo, or Brazil, or Malaysia or whichever specific geographical location your plant calls home. The rainforested areas of the tropics offer the same basic environmental properties regardless of the country. A tropical rainforest is a tropical rainforest, and the basic environmental properties of rainforests are the same throughout that entire central global belt that we call the tropics.
Learn the properties of the rainforest - any of them - and you’ve essentially learned to care for tropical plants. Any of them."
And this goes for the soil, as well.
The profile of the soil that tropical plants would naturally call home is interestingly close to the profile that we have on our property in Bonne Terre (pictured). From top to bottom, it consists of a few inches of topsoil with organic matter, followed by some number of feet of clay, followed by some number of feet of rock. The main difference between the soil profile in my back yard and that in a tropical rainforest, however, is the rhizosphere of a plant here versus one there.
The Rhizosphere. It's All About the Roots.
The rhizosphere of a plant is simply defined as everything found within the range of a plant's root system. Rhizo: root. The rhizosphere consists primarily of soil, of course, but implied in the word is an understanding of the components and properties of all that surrounds the roots: the sphere. So, understanding the rhizosphere of a plant has to do with understanding the structure of the soil, the fertility of the soil, and the microorganisms found in the soil. Microorganisms? Yes, the tiny gardeners. More about them in a minute.
Before any of this, it's important to recognize the influence that the above-ground environment has on the soils found in tropical rainforests. The rain, the shade, the temperature, and the debris on the forest floor. As mentioned in earlier sections of this post, the hydrologic cycle of a tropical rainforest keeps everything damp. And because we're talking about the tropics, we know that it's hot. And because we know the effects of the forest canopy, we know that it's shady. And because we know that all plants age and decay, we know that the debris on the forest floor would be added to daily. And because we know that there are a lot of plants in a rainforest, we know that that's a lot of debris. A lot of leaves falling, a lot of limbs, a lot of bark. And we haven't even considered the animal waste. Nor will we. The point to all of this is that the conditions that are typical in a rainforest are perfect for microorganism and other tiny gardeners to thrive and to multiply endlessly. They don't get baked by the sun, they don't dry out, and they have endless access to an endless food supply - the debris. Here's why this is important:
The fertility of any soil is determined by the microbes living in it. It is the microbes (and the ants, worms, and other small decomposers) which break the constantly falling debris into its basic elements - essentially, the microbes make the fertilizer that the forest plants need to continue thriving. A tree limb falls to the forest floor, for example. In fairly short order, a fungus begins decaying the limb. An ant colony chews and carries away the leaves, leaving debris. Earthworms begin processing the wood. Mushrooms pop up. And as these processes happen, the nutrients that were bound in the limb are made available once again to the tree from which it fell.
So how does all of this inform our tropical plant potting soil? What do we replicate?
The structure and the fertility.
The structure of a tropical rainforest soil consists of 60%-70% organic matter and the rest inorganic. The organic matter (decomposing plant debris) holds water, and the inorganic matter (pebbles, rock, sand) lets it drain. So, replicating the properties of a tropical plant's native soil is nearly as simple as following those percentages to make a soil that holds and drains water much as would happen in nature. I say nearly because the structure of the soil also includes the physical size of the ingredients. In nature, the debris on the forest floor varies in size. Some will be extremely fine particles, some will be larger, chunkier matter, and much of it will fall between those two. Making sure to have some of the bulkier matter in your potting blend adds pore space. And pore space assures that enough oxygen remains in the rhizosphere to avoid waterlogging.
Though there are many, many ingredients that can be used to achieve these properties, the tropical blend that we use and sell consists simply of 1-1-1 peat moss, perlite, and forest mulch. The peat holds water, the perlite allows it to drain, and the mulch adds pore space, holds a little water, and contributes to the diet of the micro-farmers which will chew it up and continually release its nutrients.
And the fertility? Because no potting blend that you may choose will have the same nutritious inputs (decomposing matter) that a rainforest floor will have, added nutrients will almost always be required. Everything eats, and tropical plants are no different. As with potting soil ingredients, there are endless options to consider for feeding your plants. But in keeping with the idea of replicating nature as closely as possible, we recommend a continuous feeding program.
In nature, tropical plants have constant access to low doses of nutrients. They do not receive twice annual feedings as some fertilizers are formulated for. The nutrients are always there. So, the tropical fertilizer that we use and sell is a low dose formula which is safe for use at each watering. In fact, it's a water replacement. It doesn't need to be used at each watering (though we do in our growing), but we recommend at least once per month to keep the nutrients constantly available to the plant.
The Quick Reference Version
Light - Low-Low/Medium. An eastern window is usually best for tropical plant placement - a few hours of the cooler morning sun followed by several hours of indirect light. Southern and western exposure may require positioning the plant such that it receives less direct light in the afternoon.
Soil - 70% organic (peat, bark) for water retention and 30% inorganic (sand, gravel, perlite) for drainage and pore space. 1-1-1 peat, perlite, and forest mulch is the blend we use and sell.
Water - Only once the top two-thirds (ish) of the soil has dried out. Then soak the plant and let it drain. There should always be a little dampness at the bottom of the pot, but tropical plants should not be waterlogged.
Feeding - Everything eats. In nature, tropical plants have constant access to low doses of nutrients, so this is what our Tropical Food provides. It's a water-replacement (used instead of water at least once per month, but safe to use at each watering) which provides this constant supply.