Tropical Agriculture: Vegeculture

For this blog, I wanted to do something a little different. The way that agriculture "works" in different countries around the world is very different from what we, as North Americans, are used to. When I first found out that you could grow more than one crop in a field at the same time I was baffled. I had grown up driving up and down the 401/402/403 corridor where you see nothing but endless fields of corn (or wheat or soybean or whatever it is that the farmer is growing in the rotation that year). Or, if the farm had been subdivided into smaller plots, each plot would still be its own crop. I've even driven repeatedly by a sod farm and was amazed that people actually farm grass (but I guess sod does have to come from somewhere, doesn't it?!).

In warmer climates in Central and South America, as well as almost all of Asia, some of Australia and almost all of Africa, agriculture is very different. Instead of relying on one crop for a field, a whole bunch of crops are all planted at the same time in a small area. The idea is that if one crop fails, you still have other sources of food to rely on. Very few of these crops would interfere with each other, and some might even act synergistically to increase yield. A very exciting prospect, especially as we are struggling to produce enough food for the world's ever growing population. So how does this work? It's not just a haphazard mess of plants in a dense thicket and you get what you get. There is still a significant amount of order in a tropical food plantation, and there's a lot of planning that needs to go into making sure that taller plants that will grow into trees or large shrubs won't be planted near plants that cannot tolerate shade. Plants with vast root systems should be planted near the bottoms of trees that are already established so they can't compete for resources (the tree would almost always win that battle!). This type of agriculture is sometimes referred to as "vegeculture" (monoculture planting in cooler climates is called "seed planting" agriculture), and since I was lucky enough to be able to visit a small farm in Dominican Republic I figured it was worth exploring a bit.

I present to you...vegeculture!

These first two are photos of what a typical farm plantation might look like. You can see that there's still a semblance of rows that are planted, but the rows also each have more than one plant species. There is no effort put into weeding or spraying against weed volunteers (a "volunteer" is either a plant seed from the previous year's crop that pops up during the current growing season, or an adventitious weed that grows much faster than the crop you're trying to grow). Weeds are typically short-lived plants, and if you plant creeping vines as has been done in the upper photo then this is less of a problem (or is very quickly eliminated as a problem). So what do we have here? How many crops can you actually see in the photo? Well, when I was on the farm I counted at least 8 different crops in a very small space but now (of course...I didn't write them all down) I can only see six. So let's look at each one of these using the top photo, zooming in on some that can be distinguished easily (at the very least, picked out with the help of coloured boxes...).

Red box: This plant is very, very hard to see but it's certainly worth a short discussion. Between rows, cassava (Manhiot esculenta) is planted. Cassava, sometimes called yuca (NOT yucca!) or tapioca, is planted. The crop harvested from this plant are the very deep-growing storage roots that are used in a manner similar to a potato. The downside of cassavas is that they contain cyanogenic alkaloids (aka cyanide) and must be prepared very carefully. Once prepared properly, they can be sliced and fried or mashed and are often consumed in a stew-like preparation as a side dish for chicken.

Blue box: These are pineapples (Ananas comosus)! Immature pineapple plants just look like spiky plants you don't want to come across in a dark alley, eventually growing into the plant that can be easily recognized as a pineapple plant from my last blog post (which you can read HERE).

Yellow box: This is a low, creeping vine that is often propped up (either on stakes or in a more natural form as a corn stalk or sunflower stalk) off the ground. These are sweet potatoes (which might be called yams but are NOT true yams; Ipomoea batatas), grown for their sweet, potato-like fleshy root. Sweet potatoes, unfortunately, aren't always sweet. There are definitely the sweet sweet potatoes that we are used to in North America and that Europeans are used to, but there is also another variety (some call it species) that is much less sweet-tasting. There are also very lightly coloured sweet potatoes (not the bright orange-yellow sweet potatoes we're used to) which may or may not be correlated with sweetness (up for debate).

Pink box: This very tall, grass-like crop is sugarcane. There are actually two different types of sugarcane present, one called black sugarcane (the one that's outlined in the box with the black-purple stem) and regular sugarcane (the tall grass in the purple box; both the species Saccharum officinarum). Black sugarcane, while loaded with sugar, is not used to extract sugar from. Instead, in the Dominican Republic, it is used to cook some of their traditional foods and is eaten whole when young. The regular sugar cane is what is grown for sugar extraction.

Purple box: Bananas, relatively short-lived as far as "trees" go, are often planted as a staple crop in tropical countries. Sometimes these banana trees are true bananas (Musa acuminata x balbisiana; read all about bananas HERE), while the rest will be plantains (the same species, but a different hybrid cross). They are much starchier than dessert bananas, and are much more versatile in cooking. The dessert bananas, part of the ABB subgroup, mean that they have two times the number of Musa balbisiana chromosomes in their genome than plantains, which are in the AAB subgroup (twice the Musa acuminata genes). It seems as if the back-cross, what gives that second either B or A genotype, is what determines the sweetness versus the starchiness of a banana.

Brown box: This is a coconut palm tree (Cocos nucifera which you can read all about HERE). Interestingly, there are more coconut trees in the Dominican Republic than there are people and all of them are owned by the government. If you want to buy coconuts they are delivered by the thousand (yes, that's right. The smallest number of coconuts you can buy at a time if you are a Dominican citizen is 1,000 coconuts) in a truck, and you're set for quite a while. Coconuts are one of the most versatile foods in tropical countries because they're not just used for food! If you carefully cut out the flesh you can use the leftover hull as a drinking vessel, the juice on the inside (the coconut water) can be used instead of saline solution in hospitals or cooked with, the flesh can be turned into coco butter or coconut oil for cooking (or eaten cooked or raw), and the hulls can be burned for fuel. The hulls also contain very strong fibres that can be woven into mats or cordage. You can see why they're so popular! The wood of the tree can also be used as either firewood or as a building material, depending on the age of the tree (the older the tree the less structurally sound it is, and the less likely it can be used, or would be used, to build a house).

This is just a small sampling of the number of species this one farm was growing; they also had breadfruit, mango, papaya, cotton, peppers, sage, basil, coriander/cilantro, thyme, allspice, coffee, cacao, tamarind, and annatto (to name a few...)! A pretty productive farm, and nowhere near the size of a multi-crop fruit and vegetable farm in Canada or the United States!

Unfortunately, more and more "traditional" cropping systems are popping up in Central and South America, due mostly to the influence of North American principles on traditional practices of South Americans. Sugarcane, banana and tobacco plantations are becoming more and more prominent, and are leading to serious problems with crop losses because of multi-chemical resistant pathogens that are attacking the fields. This is also leading to increased spraying, and since there aren't as strict regulations in these areas with chemicals that can and cannot be used on edible food this is being passed down to consumers in countries that import these crops. Many of these chemicals are highly carcinogenic, meaning they can cause cancer in very small quantities. Others are highly allergenic, and may explain at least part of the reason why some children are developing multiple food allergies. For example, there is a very high prevalence now of children being diagnosed as being allergic (or "intolerant") to gluten. Strangely enough, these same kids have no problem if they're eating homemade bread. It's just the bread in the bag from the mass-producer that causes them problems. Obviously this isn't a case of gluten intolerance; gluten is in all wheats, regardless of where it is acquired or how it is processed or who bakes the bread. The difference is in the number of chemicals on the wheat itself: if you bake your own bread you have the choice of where you obtain your wheat flour and if it's "organic" (however the farm or governing body defines that word) or not. A very interesting theory, and time will tell if there's any weight behind the idea!

The lemur-faced traveller's palm

Species name: Ravenala madagascariensis

Common name: traveller's palm, traveller's tree

Location: Dominican Republic (the last two photos are from Wikipedia)

The traveller's palm is native to, as you should be able to deduce by the name, Madagascar. It is still planted there as an ornamental species, and is also planted in tropical and subtropical locations worldwide for the same purpose. That being said, this species is rarely found growing in wild, undisturbed areas in Madagascar (which now are very few and far between) and so is at risk of extinction in the wild. This seems to be the case for almost every species native to Madagascar; the expanding cities due to a growing population as well as suitable lands for agriculture are putting all of their native flora and fauna at risk. It's not as short a trip as it seems to get to mainland Africa!

The traveller's palm, often confused for a member of the banana genus (Musa) because of their very similar leaf morphologies, is actually more closely related to ginger than it is to banana. It is the only species in the genus, and there are two other genera that are closely related: the African Birds of Paradise (Strelitzia), and the South American fan palm (Phenakospermum; not even remotely related to the true fan palm which I will profile in a later blog). The South American species, while very popular in Brazil, is rarely used as an ornamental species because of how easily it is destroyed in hurricanes and rain storms with high winds (the stem, while appearing very strong, can actually be cut with a single blow by a machete!).

Why the traveller's palm, you ask? Well, there are two stories for how this common name arose. First, we'll start with the biological reason: the plants almost exclusively grow in an east-west direction. Why is this the case? I don't think anyone has actually looked into why but it probably has something to do with maximizing absorption of light by the leaves. Regardless of why this occurs, it can be used as a crude compass if lost. The other reason it has this common name is because of the fact that the petioles of the leaves catch rainwater where it is stored at the base of the leaves. Rumour has it that you can drink it if you are in desperate need. But you know what else is stored at the base of the petioles? Bugs, scorpions, mud, fungal spores, and bacteria. There is NEVER a time when you should drink the water found at the base of the leaves of a traveller's palm! Even after being purified, it will still have a pretty raunchy smell.

This plant is a very cool example of coevolution between a plant and an animal. The only known pollinators of the flowers of this plant (flowers I didn't actually get a chance to photograph during my trip but Wikipedia has some lovely photos of them) is the ruffled lemur, a primate also native to, and only found on the island of, Madagascar. The long noses of the ruffled lemur almost perfectly coincide with the very long bracts of the inflorescences of the flowers, and the nectaries are actually found under the flowers in the bracts. The lemur climbs up the plant in search of a quick source of sugar, only to have their face covered in pollen of the flower. The next flower they visit has all of the pollen deposited on it, and fertilization occurs. Since they are the only animal that can pollinate the flowers, you will never see the fruit or the seeds being produced anywhere other than in Madagascar, which is a shame; they are a brilliant colour of blue!

The ruffled lemur, the pollinator of the traveller's palm. Isn't it cute?! (Photo source: Wikipedia)

Swim little fishies!

Species name: Nemanthus wettsteinii

Common name: goldfish plant

Location: UWO Greenhouse

This is one of the few tropical species of plants that grow well indoors that I'm disappointed no one has told me about before a couple of weeks ago. To me, these flowers are just plain awesome. Not just awesome for the fact that they literally look like goldfish (unlike other plants named after animals like the Shrimp Plant; sorry shrimp plant!), but because of their unique adaptations to target their preferred pollinators. The goldfish plant is native to the Amazon and surrounding areas, with the native range stretching from Brazil up to Mexico. This plant, while a very popular indoor plant in the southern United States, is still very common in the wild. It also grows incredibly easily indoors, so the need to return to the wild to collect more plants is rare.

The reproduction of this plant is fascinating. In fact, it hardly ever happens, and never happens sexually in this species. Hard to believe? I agree! But the biology has been well documented, and so here's what happens. The flowers are just an offering to species that need nectar in the wild, which is practically unheard of in the wild. This species of Nemanthus is asexual, meaning the flowers are not produced for the purpose of reproduction. Close relatives of the goldfish plant, who have redder flowers that are less shaped like goldfish and more like tubes, do reproduce via seeds (which requires sexual reproduction) so it appears as if this plant has lost the ability somewhere down the line. Instead, it reproduces asexually by severing its young branches, having them fall off the plant, ideally roll down a hill and root in a new location. In the wild these plants are often epiphytes, meaning they'll grow on just about any surface that they can grab onto (and rarely obtain nutrients from this surface; they get those from the humid air). The goldfish are just swollen sacs of nectar available for any insect or bird to exploit at their will. Hummingbirds, despite the flowers of this species being orange and not red, are still attracted to the flowers and will use it as a preferred nectar source when the flowers are in full bloom. Some insects with biting mouthparts will chew tiny holes in the bottom of the goldfish stomach to allow the nectar to freely flow out of the flower, and drink all they can get before returning to their nest. Other birds will use this same strategy, poking holes in the flowers and drinking the nectar that flows out. Every so often the goldfish plant will make something that looks like seeds when the flowers are spent, but they are sterile and not worth collecting since they will not produce a new individual (bananas are like this also; we call this not being "true to seed").

Like many succulent plants with fleshy leaves, the goldfish plant produces chemicals in the leaves that are mildly irritating to the skin. If you have sensitive skin and are planning on propagating this plant by snapping off leaves and putting them in water to root (it really is that easy to make a new plant!), make sure you wear gloves and you'll be fine. Cats and dogs (and other indoor pets) usually stay away from this plant despite having flowers that look like they would be fun to play with. There must be some kind of scent emitted from the leaves or flowers that lets them know it shouldn't be messed with. Goldfish plants are quite drought tolerant, so ignoring them won't bother them too much. They are also frost-tolerant (reportedly surviving brief exposures of -5 degrees Celsius or about 23-25 degrees Fahrenheit) so forgetting them outside on a cold night isn't a big deal.

A word of warning, however, if you like using these plants as ornamental garden plants in baskets during the summer and have a backyard garden: they carry viroids. A viroid is like a virus, being able to be transmitted from plant to plant when they come in contact (or when the sap of one plant is on the leaf surface of another, where it can enter the leaf breathing pores or stomata). Viroids are present in many plants, and it is believed that some are just the result of a virus that had infected the plant but had mutated to no longer be able to reproduce so gets stuck in the plant as a sort of virus fossil or relic. Some viroids, however, are still able to cause disease in plants, especially crop species. The viroid that the goldfish plant carries causes no symptoms in the plant so you would never even know it had it...until it comes in contact with either potatoes or tomatoes. Then it wreaks havoc. The symptoms in potatoes and tomatoes are quite severe, reducing the yield of crops of these two plants quite drastically. Best to keep these plants away from each other! Viroids cannot be spread through the air, and this particular viroid doesn't last very long outside of the plant, so having them in the same garden is no problem as long as there's a distance between them.

The palm with the pony's tail

Species name: Beaucarnea recurvata

Common name: ponytail palm

Location: UWO Greenhouse

The ponytail palm is not a true palm, and its closest relative might surprise you. It is native to Mexico, but is used as an ornamental plant throughout much of the southern United States (it is cold-hardy to 6 degrees Celsius and is incredibly drought tolerant), South America, tropical southeast Asia, and Australia. This "tree", like true palms (one of which you can read all about HERE), is not actually a tree at all. It has no tissue called the vascular cambium, which is responsible for producing secondary xylem which is what we refer to colloquially as wood. If you don't produce true wood because you don't have secondary xylem, you can't be a tree! There are many monocots that masquerade themselves around town as being woody; bamboo, lucky bamboo (a completely different group of plants), palms, tree ferns and bananas all lack the ability to produce true wood (you can read all about bananas HERE). This doesn't mean that we can't use them as building material! All of these species produce a tissue type called sclerenchyma in great volumes which contributes to their stem stability (except banana; they produce collenchyma which is a tissue very similar to sclerenchyma. They also don't have a true above-ground stem!).

The ponytail palm, as mentioned, isn't a palm at all. It's actually a close relative of the asparagus family, and if I had of caught this plant while it was flowering it would have been much more obvious. The flowers produced by this species are almost identical to the flowers you would see if you let the asparagus in your garden go to seed. It's amazing the kinds of morphological variation you can get within a family!

The swollen base of the stem of this plant is designed for prolonged periods of drought. It almost acts as a water canteen, which can allow the plant to go for months without a significant source of water. If the plant went long enough, the base of the stem would start to shrink as the tissue and the water it contains starts to be reabsorbed by the plant. During the next major rainfall, the plant would reabsorb its water again and regrow the swollen stem base.

What's the name of this plant again?

Species name: Ginkgo biloba

Common name: ginkgo, maidenhair tree

Location: Ontario

Up until relatively recently (late 1700s to early 1800s), this species of tree was well known from the fossil record (along with the approximately 8 other species in the genus) but believed to be extinct in the wild. There were a few living specimens known at the time in China, Korea and Japan that had been cultivated and tended by monks for thousands of years, and so they were considered to be, quite literally, living fossils. Two stands of trees were discovered in China and from those two remaining small populations, all of the rest of the trees in cultivation around the world were derived. Unfortunately, it was discovered recently that the two remaining natural populations show an incredibly high level of genetic uniformity (suggesting they might, in fact, be two "families" of trees and therefore very closely related to each other) which puts them at great risk should a pathogen develop that targets ginkgo trees. This probably isn't an "if" and more a "when"! Like bananas, all of the ginkgo trees would be wiped out if we couldn't come up with a solution in time. Similarly to the Dawn redwood, the ginkgo tree is monotypic, meaning that it is the only remaining species in the genus, and all of the rest of the close relatives to this species are known only from fossils. You can read all about the Dawn redwood HERE. Interestingly enough, the Dawn redwood, like the ginkgo, is also critically endangered in the wild.

There are two characteristics about the ginkgo that are worth noting. The first is that these trees are dioecious, meaning that there are separate male and female trees. If you're planting a ginkgo tree on your property for purely ornamental purposes, make sure you choose a male tree! The female trees are the ones that bear the fruits, and the fruits have a hideous smell (think of the smell of rotting, rancid butter and that will begin to describe it...) that lingers throughout the winter with every temporary melt of snow. If you would like to plant the tree to consume the seeds for their reported medicinal values, make sure you plant both a male and a female tree to ensure large amounts of seed production. The second interesting characteristic about this tree is that they don't actually produce fruit, because fruit can only be produced by Angiosperm trees and this is a Gymnosperm. This means that the ginkgo, despite looking like it has broad leaves (similar to something like a maple or aspen or oak) it actually has modified needles (like pine or spruce or a cycad)! The "fruits" are actually just seeds with a swollen outer surface called a sarcotesta, and is developmentally very different than the fleshy part of a fruit. Once that layer is removed (should you attempt this insane, smelly feat, WEAR GLOVES! The smell, once on your skin, has to be leeched out, not washed out!), the remaining seed "shell", the sclerotesta is revealed and it looks a whole lot like an unopened pistachio (but a lot bigger).

The ginkgo seeds are culinary delicacies in many locations around the world, not the least of which being in China where it is used in large amounts around Chinese New Year in a dish called Buddha's Delight (if you've never tried it, you must! It's delicious). The Japanese and Koreans also make dishes that feature the ginkgo seed, and they are served year-round (but more so on special occasions since they are expensive). The other main use of this plant aside from its culinary and ornamental uses is the medicinal use. This is actually one of the suggested reasons for the decline of the population of ginkgo trees throughout its native range. Other theories state that massive ecological changes caused drastic declines in population and the ongoing medicinal value of the plant was the straw that broke the camel's back, so to speak. Regardless, there are now plantations in China for the dedicated medicinal use of this plant.

Medicinally, the main claims to fame with ginkgo and human health revolve around memory and dementia. First, it is claimed that ginkgo supplements help with memory retention in the aging process. It is suggested that if you consume 240 mg of ginkgo extract per day it will improve your long-term memory and help prevent the onset of Alzheimer's disease. In a very large study in 2008 done by the Journal of the American Medical Association, there was no effect of ginkgo extract consumption and memory, or a correlation between ginkgo consumption in any form and the onset of Alzheimer's. People who consumed ginkgo were just as likely to get it as those that didn't. A much smaller study in 2010 by the American Geriatric Society published in the Journal of Geriatric Psychiatry showed that it had a significant effect over a placebo in people already suffering from Alzheimer's (or other diseases that are Alzheimer's-like) on memory retention. A third study showed that for up to 2.5 hours after consumption, ginkgo extract and ginkgo seeds had a significant effect on memory retention in memory-recall experiments in healthy people. So far there are no studies that show that ginkgo is harmful to your health, so if you choose to take it to improve your memory at the very least it will do nothing. But until more large-scale scientific studies start agreeing with each other, take all reported effects with a grain of salt.

Ginkgo extract does act as an anti-coagulant, so as with all medications (herbal or not), make sure you consult a doctor before taking them to make sure it won't interfere with anything you're already taking. This especially applies to those at high-risk of stroke who are already on blood-thinners like warfarin (yes, the rat poison warfarin is now a medication for humans!) or coumadin, since even a minor injury could lead to massive blood loss.

Look at all those hands!

Species name: Musa acuminata x balbisiana

Common name: Banana

Location: Panama

The genetic origin of bananas has only recently been discovered through DNA sequencing. Traditional views of the banana parentage say that there are about four distinct species of banana that we use in cultivation today, each species having been genetically modified through traditional breeding methods to arrive at roughly the same banana shape, colour, taste, and growth pattern. Each species would have referred to a different size banana, either a "traditional" banana, a finger banana, plantain, etc. Now we know that the banana we can buy in grocery stores in Canada is all one species, and its a hybrid of two wild ancestors. I should also mention that technically a "bunch" of bananas isn't really a bunch. If you want to sound all technical and fancy when you refer to your bundle of bananas, call them a "hand" as those "in the know" do.

To say that the banana we eat today is all one species isn't quite going far enough. Banana plants everywhere are actually all CLONES of each other, meaning that they are all genetically identical. The specific strain or variety of banana that we grow today is called the Cavendish banana. For those of you not in Biology or with a Biology background you might be thinking "so what? We got what we wanted out of the plant, and now we want it to stay how we like it. No big deal". Well, this is actually a huge deal. The banana plants that we grow today have no resistance to a recently discovered fungal strain called Fusarium TR4 (Tropical Race 4) which attacks the roots of banana plants. This has the potential to completely destroy the entire population of banana plants and so a lot of people recently have been saying that the common banana is at risk of going extinct. Then what? Well, then we have no more bananas. In the 1820s something similar happened to a variety of banana called Gros Michel, which was the most widely consumed variety of the time. This concept of complete devastation of an agricultural crop due to disease isn't new; we've been suffering with this problem as humans since we made the switch to an agricultural life almost 14,000 years ago.

What's special about bananas? Well, for one they don't have sex. This is incredibly unusual in the plant kingdom for a plant to not only reproduce parthenocarpally (in other words, each banana is produced from one female flower without the input of pollen from a male flower), but also to produce a large, fleshy fruit from this as a result. A second unusual trait about bananas is that they're not actually trees, despite how big they get. In order for a plant to have the potential to be a tree, it must produce a structure in its stem called a vascular cambium, which bananas cannot do. They might be tree-like, but they're not trees. Now you can correct everyone when you're visiting a banana plantation in a tropical country!