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Why are all the colorful woods from the tropics?

3K views 27 replies 18 participants last post by  NoThanks 
#1 · (Edited by Moderator)
This is a question that has been eating at me for a year.

When I look through the Wood Database and my local lumber store I notice that the really colorful woods (e.g. bloodwood, purpleheart) all come from trees native to hot, southern regions. Principally, it seems, South America and Africa.

To my knowledge, wood native to North America is usually some variation on brown or white.

But there are many "exotic" woods that are potently red, yellow, orange, purple, and jet black.

Assuming my premise is correct, why is this? Is there something about hotter, tropical regions that causes trees to give up wood with interesting colors? Is it just coincidence?

I have researched this and haven't found an answer. My initial idea was that heat=colorful wood but I think that's way too simplistic and couldn't find any evidence to support it.

Opinions?
 
#2 ·
This is just a guess, but most wood color is somewhat created by the minerals the tree sucks up in the water it needs to live.

There could also be something to be said for a strange wood color ( and possibly accompanying smell), being a defensive device against wood boring insects, of which there are many in the tropics. So evolution over time would come into play.

That's it - I'm out of ideas!
 
#3 ·
What do you call a dear with no eyes? No eye dear… What do you call a dear with no eyes and no legs? Still no eye dear… I've no idea :)
 
#4 · (Edited by Moderator)
There are quite a few colorful woods from North American trees. Osage Orange and Mulberry have yellow heartwood, redwood and cedar have gorgeous red/orange tones, poplar and cottonwood can be very green (I think that's related to the minerals in the soil that Tennessee mentioned). I have some honey locust that has a lot of pink coloring mixed with the tan. I know there are a bunch of others I am missing or not familiar with.

I think the perception comes from a couple factors. Most species of tropical wood are brown, we just don't import as many of those. After all, we have plenty of native lumber that is brown tones, so the main species of interest are the ones that look dramatically different than what we have locally that is cheaper and easier to find. The other factor I can think of is that tropical trees tend to grow larger than most North American hardwood species, making them more viable for lumber. For instance, Osage Orange is beautiful wood, but the trees are generally smaller and very regional, so not a reliable source for yellow colored wood.

The more interesting thing to me is that I don't know of any colorful North American woods that will not eventually fade to some shade of brown without protection from exposure to UV, while there are quite a few tropical species that will maintain their intense colors such as yellowheart and bloodwood. Others, such as purpleheart, fade to brown just like native woods.
 
#5 ·
I would speculate that the tropics have more diversity of species. If you have 5,000 types of trees (just throwing out a number) instead of 500 you are bound to have some that are more unusual. We have discovered the unusual species and used them for their colors.
 
#6 ·
I think it's probably mostly what live edge said, but just guessing. What JayT said makes sense too though.

I've heard of a theory of why tropical plants and animals tend to be more brightly colored but I doubt it would relate to the color inside trees. I'm not even sure it was a well supported theory.
 
#7 · (Edited by Moderator)
Hi Purrmaster. Be careful, if this is something you really are interested in…. it is a rabbit hole if you use the right resources and searching skills, but over all that's a great question…

Trees from the warmer climates have a lot more stuff to grow in and absorb… chemicals of all sorts are in tropical trees because they need to be very competitive to survive other plants and far far more animals, insects, and microscopic plants and animals than the colder climates. Each tree develops something to be competitive based on where they grow best. Sometimes this is in colored clays and ketone rich soils… which can be different every few miles depending on the foliage, changes during rainy seasons and flooding river banks… not to mention the constant cycle of life and death (without a sleeping season we have up here in the cold) allows for one species to become dominant and specialize their traits and then change the soils for future generations, like Bloodwood does. The oils and hard saps in many tropical trees also help give color due to prismatic crystalline structures in the tylosis, phenols, and other metallic and mineral absorption and occlusions. Which most trees in the northerns climates also have to some amount, but are not as specialized because there is less to grow in and compete with …. and thus get to focus most of their time on propagating: shooting out saplings and seeding over long distances until they can form stable dominate forests out of grasslands through successional stages. A luxury tropical trees don't get. Think of it as similar to fish.. the more variety of fish there are in one small area the more colorful they become… where most fish here in Illinois are brown and grey with some small splash of color. There is more of each species of fish, making them easier to catch and eat, but not very pretty to collect in a fish tank.

Now I am no expert and I may have some things wrong, but I am truly interested in understanding how trees grow and why.. and how that relates to my woodworking. I highly recommend my favorite book: ""The Tree by Colin Tudge ... and researching the botanical tree names not the common nor the wood name (which can be very wrong and misleading). Hope I helped some. :)
 
#8 ·
It has to do natural selection. Woods in the tropics are constantly under attack from all manner of insects, 24/7, year round. Trees have adapted and evolved by producing resins and oils that deter insects. Those resins and oils give wood it's color and is also why some people develop allergies to tropical woods.
 
#9 ·
Closer to the equator = more sunlight. Sunlight is made up of colors. More sunlight = more colors. It's really quite obvious when you stop to think about it.
 
#10 ·
An excellent set of responses. Thank you!

I thought I had read somewhere that some trees do indeed take up minerals from the soil. If the minerals are the source of the color I wonder if we could "colorize" northern trees by planting them in certain soils or injecting minerals. Probably not. Do we know what minerals colorful woods like yellow heart soak up?

Your point about the diversity of species in the tropics is a good one. If you've got a zillion tree species you have more chance of coming across a tree or two with strange color. But still, we have many species of trees in the north but I don't see anything that looks like bloodwood.

I looked up osage orange. Isn't it from the more southern (hotter) part of the US?

I know trees put out saps and resins as protectives. Evolution selecting for that ability makes sense. But why red and purple and yellow? Is not pine sap either clear or light orange? And how often would a tree be showing it's colorful wood to the world? Especially if the color is in the inner heartwood. I'd think you'd have to bore in pretty deep to see that.

I don't know what the color spectrum of various tree eating critters are but I thought there were not many animals that could see the range of colors that humans can. I admit, once again, my premise could be faulty.

I'll look for that book at the library. Thank you. I like rabbit holes.

As for color fading… I think the color in woods like purpleeart comes from a natural dye that the tree produces. Dyes (both natural and artificial) fade when exposed to sunlight. I think the UV light breaks down the chemical composition of the dyes.
 
#11 ·
I'll be the devil's advocate on a few of the theories, just to poke holes (although they may still have validity).

If the color comes from the soil, why aren't our trees different in Georgia? Have you seen how red the soil can be in Georgia? (or other places)

If the color comes from the soil, why don't we see a variety of species growing in the same area have the same coloration?

If the color comes from insect defense why do we often see a difference between heartwood and sapwood? It would seem the defense would be most helpful in the sapwood, but many of the colorful trees are only colorful in the heartwood (purpleheart comes to mind).

I'm guessing the answer, actually, is more than one answer. Each tree species has color for different reasons.
 
#12 · (Edited by Moderator)
Well for Bloodwood ~ The trees grow the best in higher dry soils away from flood areas. They are most fond of soils that contain Carbon, Magnesium and Iron (Ferric Oxide)... when added to Aluminum Oxide, Manganese, and a strong acidy soil… the clay essentially turns red. Since Bloodwood is not a water dwelling tree, it does not produce oils or mucilage cells, instead to retain moisture it has tanniniferous (latex) cells, which easily takes on the red color of the soil… as does the budding leaves and fruit. Since the trees prefer to form dense groves in stable ground, most saplings grow from the decay of older trees and recycle the red over and over… farmed woods have been known to have a less pure red and more stripes of reddish tan.

Bloodwood has chalcone derivatives and a prenylcoumarin that can affect men's androgen health.

As for Yellowheart ~ it prefers to grow in red-yellow Podzolic soil… rich in Aluminum, Carbon, Iron, Nitrogen and Phosphorus, and Diphosphorus Hexoxide… and absorbs the Kaolinite clay mineral (composition Al2Si2O5(OH)4)... it is a layered silicate mineral produced by the chemical weathering of aluminium silicate minerals like feldspar. It is colored pink-orange-red by iron oxide, but Lighter concentrations yield white, yellow or light orange colors. The Iron is also why it tends to darken after a time, so the richer the yellow, the more it will darken.

YellowHeart as alkaloid that can affect a woman's reproductive health.

I know nothing about Purpleheart… Yet!!
 
#14 · (Edited by Moderator)
Let me see if I have this right. The trees that are colorful suck up minerals in the soil. But only certain trees will grow in soil with those minerals. Presumably that's an adaptation so they can utilize areas other trees cannot tolerate.

So the trees that prefer or can tolerate soils with high loads of certain minerals happen to be the ones that are colorful? Other trees are not because they don't grow in those soils?

The mineral theory is actually the most compelling one I've heard so far. But that still leaves the question… why do these trees develop only in warmer areas? What is it about northern cold that doesn't produce mineral sucking trees? Once again, my premise could be wrong. As pointed out above: aromatic cedar's purple color kind of blows my a hole in my premise.

And I'm still curious about Live Edge's point about only the heartwood being brightly colored? Wouldn't it be uncommon for any critter to be able to bore so far into a tree as to hit the heartwood?
 
#17 ·
Another possibility may be that during the glacial period(s) a lot of the trees that survived and flourished in warmer temperatures died off. Then when things warmed up a bit the 'tropical' trees were kept at bay by either geography or other tree species. I have no evidence of this. It's just a thought.
 
#18 ·
I question the premise of the OP that all, or even most, of the colorful woods come from the tropics. We have a pretty wide range of colorful woods in North America, ranging from pure white (holly), yellow (locust), green (poplar), orange (osage orange), pink (dogwood), red (aromatic cedar, cherry), and many others. Walnut can even have red and purple hues. South Africa and southern Australia are both at about the same latitude south as our mid Atlantic states are north, and they both produce some beautiful and colorful woods. Aside from bloodwood, purpleheart, and perhaps a handful of other species, what are all these tropical hardwoods that have such eye-popping color that so far exceeds those found in North America and other temperate regions? There is no question that species diversity is much greater in the tropics than in northern latitudes, so as others have mentioned, one would expect a somewhat broader range of colors, as well as other wood characteristics, in the tropics. I don't believe the soil mineral theory holds water at the species level. Individual trees can have areas within their wood that have mineral stains, but we have many tree species that range across vast areas and many different soil types, and yet their wood is basically the same color wherever they grow. We are blessed to have an abundance of fantastic wood species in North America. For beauty of color and grain, and for utility and workability, they are hard to match anywhere in the world. I think it may be a matter of we are so used to the woods we have here, that we tend to gravitate towards something different.
 
#19 ·
Please do question the premise :). I again looked at osage orange and it appears to prefer warmer areas like Texas. Dogwood grows all over. We used to have a dogwood tree and I'm in Oregon.

I guess what I mean is that the colors of wood from northern climates tend to be less intensely colored. Dogwood is a pinkish/creamish color. But bloodwood is deep red. Padauk is bright orange. So by colorful I guess I'm also referring to the potency/brightness of color. Even if there is color in northern woods the colors tend to be more muted. Walnut is dark brown/black but ebony is black as night.

Just to be clear: I'm not knocking American hardwoods. My favorite wood is walnut.
 
#20 ·
Not all ebony is black. Some is even cream colored. Blackwood from South Africa (not a tropical latitude), on the other hand, can be quite black. Granted bloodwood and padauk are brightly colored, but again I've only heard a few species mentioned that are brightly colored. Most trees growing in the tropics have wood that is no more colorful than many of our more northerly woods. I think you are taking a few examples and over-generalizing them.
 
#21 ·
Please do question the premise :). I again looked at osage orange and it appears to prefer warmer areas like Texas.
While Osage Orange's original range was mainly in Texas, it is now found over most of the US and even up into Canada.



Osage (hedge) fenceposts are shipped out of Kansas by the thousands and our climate is definitely not tropical.

But bloodwood is deep red. Padauk is bright orange. So by colorful I guess I m also referring to the potency/brightness of color.
A lot of that is because the only wood imported and sold is that which has the better coloring. I've had a few pieces of bloodwood that were more reddish brown than deep red and I'm sure a lot gets cut that is more brown and thus not nearly as valuable for sale, so doesn't get exported. There is a good video about Taylor guitars and the use of ebony here where Bob Taylor talks about how the people harvesting ebony trees were leaving all the ones that weren't deep black to lay and rot because they didn't have enough value to haul out. (the whole video is good, but that part starts about 6:30 in) No different for other species.
 
#22 ·
I would back what LiveEdge says as a guess. South American mountains run north to south and probably allowed for lots of species to survive the ice ages and whatnot. Our mountains do, too, and we enjoy a much richer diversity fo species than say, Europe, which grew its mountains the wrong way-East to West.

But ya, I wish that purpleheart grew around me in New York!
 
#23 ·
Another thing to consider is the seasons. Close to the equator there are two rainy seasons and two warm dry seasons a year. But never cold. They dont get a dormant winter like the northern hemisphere does. So that alone will make the characteristics of the wood very different. Very different growth rings.
 
#25 ·
It would appear I've been hoisted on my own petard as far as osange orange goes. (I've never seen any locally, unfortunately).

You're right that tropical/southern areas have no real cold season. That was my initial hypothesis as to why the brightly colored woods come from warmer regions. But I have no idea why heat would cause that.

I'm thinking it is the minerals. Perhaps the minerals available for trees in northern climates aren't as colorful. Or perhaps northern trees don't need those minerals. If the minerals are being used by the tree as a sort of natural pesticide perhaps northern trees face less pests.

Of course the emerald ash borer is kind of shooting down that theory.
 
#26 ·
Of course the emerald ash borer is kind of shooting down that theory.

- Purrmaster
Not really. The emerald ash borer is not native to North America. It came over from China, probably in shipping crates or pallets that weren't treated for pests, so our native ash trees have no natural defenses. The ash borer will lay eggs in other species of trees, but hasn't had the disastrous effects seen in the ash population. Something in those other species is holding back the borer larvae.

Tropical vs northern definitely affects grain patterns. Tropical woods tend to have interlocked grain with consistent patterning, while our native trees have the early & late wood patterns that can vary widely depending on that severity of seasons, water availability, etc.
 
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