Monday, February 4, 2008

Bad Influence (Coffea arabica)

This is in fact the same plant as the one that gives us commercial coffee. As the botanical name suggests, it's from the general Horn of Africa area, though the specifics are still being argued about, particularly the question of whether it was first farmed on the African or Arabian side of the Red Sea.

The general area where Coffea arabica is native; Ethiopia, Somalia and Yemen in particular. (I couldn't find an actual range map: consensus seems to be that it all started in Ethiopia somewhere.)

We also, of course, have no real idea who first cultivated it, either. There is a cute and almost certainly false story involving an Ethiopian goatherder: the story says he noticed that goats eating the berries became more playful and energetic (for some reason almost every account uses the word "frisky"), tried them himself, and then went on to farm the plants purposefully for the beans. This story almost has to be leaving out a few important developments, like for example whether the berries or the beans were the initial justification for early coffee farmers: the flesh of the berries is edible, and apparently tastes good, though it doesn't contain caffeine as far as I can tell. But in any case, we can glean at least this much from the tale: 1) it was a long time ago, 2) Starbucks didn't invent coffee, and 3) people like caffeine.

(A more thorough and interesting story, including an explanation of why we associate the word "mocha" with coffee, the theft that led to the first European coffee production, and the highly caffeinated political radicalism that started in the first coffeehouses, can be found here, at the website of the International Coffee Organization.)

Coffee growing is now an international business, and almost 80% of the coffee produced is from Coffea arabica. Most of the world's crop is from Brazil (about a third of the total), but there are other coffee growers in Central America (Mexico, Guatemala, Honduras), Southeast Asia (Vietnam, India, Indonesia), tropical South America (Peru, Columbia), and its native Africa (Ethiopia), as well as smaller growers scattered elsewhere around the world. In the year 2000, U.S. consumption of coffee was 22.1 gallons per capita; in that same year, my own personal consumption was probably about 500 gallons in a year.1

The remaining 20% of coffee that is not Coffea arabica is from Coffea canephora, a related species with higher caffeine content but a harsher taste. C. arabica is the more delicate plant, and are more susceptible to burn (especially at low altitude) and certain diseases, but it produces the superior beverage.

There are a few varieties and cultivars of Coffea arabica, including some crosses with C. canephora, but none of them are exactly household words, and aren't especially relevant to houseplants. There is one variety, referred to here as "purpurascens," which supposedly has purple leaves, but I couldn't track down any pictures, and in any case it's not something you see in stores. Maybe someday?

C. arabica is in the family Rubiaceae, which is also home to Gardenia jasminoides. If you tilt your head and squint a little bit, you can kind of see the family resemblance: both have very glossy, dark green leaves, with white, fragrant flowers.

Coffea isn't as difficult a plant indoors as Gardenia, but it's still pretty demanding. My own big issue, and at least for the moment, the biggest issue for the plants at work, is temperature: although the greenhouse is warm, there are cold spots, or spots where roof condensation causes persistent cold drips (previously mentioned in Ficus maclellandii). The largest of the Coffea arabica at work (which has since sold, but is pictured below) has been dropping yellow leaves every now and again, and my much smaller plant at home is doing the same thing. I would be more worried about this if not for the fact that I've had a customer ask me about the very same behavior on her Coffea at home, and I recently saw a large plant with berries and everything in another retail greenhouse that was also dropping leaves. I figure this more or less clinches it: yellowing leaves during winter has to mean either that the plant is too cold (which is plausible for all four of my examples) or that this is a normal reaction to shorter day length. In either case, it's a winter thing, and there's not a whole lot I can do about it.

The biggest of the work Coffea arabica plants, since sold, which very sneakily started branching and going all treelike while still in its original four-inch pot. By the time I noticed that it was shading out neighboring plants, it had developed to this point and had to be moved up to a six-inch pot.

Come summer, the big issue will be water: C. arabica transpires enormously when it's in full growth mode, and consequently it needs to be watered a lot, even inside in an air-conditioned living room. In the greenhouse at the end of last summer, we were needing to water the Coffea and Codiaeum variegatum two or three times a day. (Meanwhile, many of the other plants were scorching, or notching,2 or otherwise falling to pieces.) Both over- and underwatering can be problems: with mine I water when the pot feels noticeably light, and that's worked okay so far.

Other than those two things, you're basically aiming for a tropical, really tropical, rainforesty kind of situation: high humidity (too little will get you brown leaf margins) and high light (pretty much the more, the better, though this has to be eased into gradually or the plant will burn). Some sites say east or west exposure, with the implication being that south is too much: I think south is the only reasonable place to put them, so we have ourselves a controversy. I wouldn't put a Coffea in full sun outdoors, though, just so we're clear: though they do eventually get to be tree-sized, I'm told they need shade when they're younger.

None of the Coffea arabicas I know personally have been especially prone to pests, and they're not likely to need any more grooming than just the usual removal of dead leaves. They are supposed to be pretty heavy feeders, though, and every site I've seen that addresses soil at all is very insistent that they need soil with really, really awesome drainage. No particular kind of food is necessary, as far as I can tell, so long as there is some: 20-20-20 should work just fine, mixed according to the label directions and given once a month or so.

But what you're really interested in is, can I grow my own coffee beans at home, right?

Well, it's not likely to be practical. But.

Plants are mature enough to flower at around three or four years old, and will, if given good enough conditions, flower every year thereafter. Flowers are white, fragrant, and star-shaped, and are produced along the leaf axils.

Coffea canephora is dependent on cross-pollination, but C. arabica, with twice as many chromosomes (44, compared to canephora's 22), is self-fertile and will fruit without any intervention on your part.3 Berries (sometimes called coffee "cherries") will form, but they take roughly nine months to ripen. Ripening is signified by a change in color (they turn red, hence "cherry"), and doesn't happen all at once: berries that are right next to one another don't necessarily ripen at the same time. The flesh of the "cherry" is edible, though most of the weight and volume is taken up by a pit, which usually contains two seeds (the coffee "beans" you're familiar with). Once in a while, three seeds are found in the same pit; slightly more often than that, there will be only one seed. These solo beans are referred to as "peaberries" and have a different flavor than the regular beans. Peaberries are often separated out from the batch and sold separately, at a higher price.

Beans intended for beverage use must be roasted before they can be ground: roasted beans have a better flavor, apparently. I'm not going to go into the specifics of how you roast your own coffee beans, but you can find a description of the process here and another one here, if you're really that interested.


Beans for propagation also go through some changes: in the wild, they're usually passed through the digestive tract of a bird, because, um . . . well, who among us doesn't want to be passed through the digestive tract of a bird?4 If you're germinating your own seeds at home, this is probably not going to be practical, but that's okay, 'cause it's not entirely necessary either. Seeds which have been removed from their pits and allowed to quietly dry somewhere can be planted; this site says that the best germination rate is observed for seeds which are about eight weeks old. I'd assume bottom heat would be helpful for germination, and probably also a humidity tent, but I didn't find any specific instructions for how to do this, so your guess is as good as mine, I suppose.5

Propagation from cuttings is also said to be possible, but apparently it's not done often, and when it is done it doesn't succeed that often. I haven't tried it myself, but I would guess that bottom heat and a humidity tent would be useful here too.

Coffea arabica will get to be a tree, in time, if not routinely pruned back. 40 feet (13 meters) is not unheard of. On coffee plantations, plants are pruned to keep them at a convenient height for harvesting, usually around 6 feet (2 meters). Individual plants can be very long-lived, as well: they begin to produce fruit at about 3 or 4 years old, reaches its full yield at about 6 years old, and can live to be 60-100 years old, given good conditions.

My personal plant, late October 2007

In keeping with the vague quality of drug-pusherness surrounding the plant, it's also somewhat noteworthy that Coffea arabica has become invasive in the Australian rainforest. (hat-tip to the Invasive Species Weblog for the link) The article doesn't say, but I'm guessing that the relatively quick growth and abundant, animal-spread seed, probably have a lot to do with its success. I was unable to find evidence of invasive Coffea plants elsewhere, though that doesn't mean it hasn't happened.


Photo credits:

map: public domain from a site I can't remember
work plant, my personal plant: me
flowering plant, "cherries:" Marcelo CorrĂȘa at the Wikipedia entry for Coffea arabica


1 You'll be happy to know that this is down to the much more reasonable 180 gal/yr. I was working, for most of the year 2000, as night auditor in a motel, and the actual paperwork I had to do only took me a couple hours: I had nothing to do between about 1 AM and 5 AM except smoke and drink coffee, and consequently developed a bit of a dependency on both. "Bad influence" indeed, though I do loves me some coffee, so I don't feel especially guilty about this. (The math: 12 cups before work and about 10 cups while at work = 22 cups/day. 22 cups/d times 365 d/yr times 1 gal/16 cups = 501.8 gallons / yr. Now it's more like eight cups a day, which I think we can all agree is quite moderate by comparison.)
2 "Notching" is a quirky little thing that Dracaena deremensis (especially 'Warneckei') does when it's too hot: incoming new leaves develop what look like cuts, at the base of the leaf. The growers' guide says that light foliar sprays of boron will make it stop happening, but any damaged leaves will remain damaged. For indoor growers, the more sensible approach to notching would be to move the plant out of the heat and light that's causing the notching in the first place. I don't think it's very likely to happen indoors anyway. D. deremensis also get a mosaic-type pattern where the veins stay green but everything else yellows (this is called chlorosis, or netting), and although they will return to green when temperatures go back to normal, getting back to normal takes months.
3 One of the weirder things about being a plant is that every once in a while, a plant inherits a whole extra set of chromosomes from a parent, or spontaneously doubles its own, and still functions perfectly well as a plant. Often, there is also an increase in the number for some part of the plant: ten petals on the flower instead of five, bigger fruit, more seeds. This situation is referred to by the technical name "polyploidy," and it's fascinating stuff, if that's the kind of stuff you find fascinating. Polyploid animals also happen, with some species being entirely polyploid. In most cases, of course, having a whole extra set of chromosomes will just fuck you up: double your chromosomes at your own risk.
4 (Hey. Don’t judge.)
5 (No it's not. My guess is totally better.)


Anonymous said...

Plants that are very similar to the coffee plant (and that have edible fruit) and grow wild are eaten (the fruit, that is) across a large area of Africa. That should be taken into account when thinking of scenarios for domestication of coffee.

Tracy said...

I have always wondered if a person could get their own coffee beans from this plant, thanks for the answer, I might have to try. I've got the 400W to cheat So is there a way to judge the age of the plant by the size? I would get one from a nursery, but obviously to speed the process, I want an older tree. Awesome post!!

mr_subjunctive said...

I suppose in an approximate kind of way, you could judge age from size, but I'm not sure where you'd have to draw the lines exactly. The only plant I've ever seen in person that had berries on it was roughly four feet tall: one doesn't see many of those for sale. My guess is that the plant in the second picture of this post, the work plant, was probably about one or two years old, and it was two feet tall (give or take).

Tracy said...

Thanks, that at least gives me at least something to go on.....bigger plant, possibly 2 years. I just want to make sure I don't get some newly planted seedling or Are the ones in nurseries grown from seed too?

mr_subjunctive said...

Not sure, but I'm guessing probably they're mostly seeds. Cuttings don't seem to work all that well, and unroasted coffee beans, at least in theory, should be cheap, abundant, and easy to transport. So I would be really surprised if most of them weren't produced from seed.

waterroots said...

Great post. Lots of interesting info...

I've grown this plant in the past and although they are not the toughest to master, they are a little demanding. I haven't seen them around for awhile at the local stores; they seem to come and go. After reading this post, I'm tempted to try my hand at this plant one more time...just one.

Karen said...

Is there a trick to pruning? I'm always excited when the new leaves sprout at the tips of the branches and would hate to cut off the new growth.

cruz4him said...

We got lucky at our office last year. Nature Valley (granola bars) had a promotion in my building and they gave away small c.a. plants along with the bars! Pretty much everyone in my office has one or two. However, I can say with all smugness that mine are definitely the best of the lot, due to a lot of attention to watering (usually twice a week) and a large south window that gives it a lot of indirect light thanks to a huge building in front of me that blocks off the harsher rays.

I'm interested in the pruning question, too, though. I love how bushy this gets at the top of those super skinny legs so I wouldn't want to do anything that might ruin that aesthetic. Any tips?

Anonymous said...

I have been growing mine in my apartment in college for about a year now. I am so glad I found this blog because every time something happens to mine I panic like a new mother and her baby. I love this blog and I hope you keep us updated. Thanks

Anonymous said...

Mr. S -- can you please post an updated pic of your coffea arabica? I'm interested in seeing how it's grown since 2007 and want to compare it to mine.

mr_subjunctive said...


Tomorrow's (28 Feb 09's) post will have a new pic for you.

Anonymous said...

I've read coffee plants (both species) are moderately invasive in India, but it is only really a problem where a plantation directly abuts a vulnerable habitat, which kinda indicates the coffee isn't the biggest problem.
Also, polyploidal plants are fascinating. My favorite example is Sequoia.

kestrel said...

I bought a 3 inch pot at the grocery store with a whole bouquet of coffee seedlings. I just kept one and put it in a larger pot... Part sun, plenty of fertilizer. It bloomed after a year an a half, and berries didn't ripen until about a year later.

AnnadlC from Toronto, Canada said...

Hey Mr S! Do you still have this plant hanging around? Have you been able to make any coffee from the beans? I'd love to see a new pic of what it looks like now!

mr_subjunctive said...

AnnadlC from Toronto, Canada:

Yes and no; the biggest of the seedlings in the original plant's pot died of unknown causes a couple years ago, but at least one of the other ones is still around. I'll put getting a photo of it on my to-do list, and I'll probably get that done relatively soon, but don't hold your breath to see it on PATSP, 'cause it'll take a while.

Haven't tried to made coffee from the beans: instead, I (foolishly?) tried to germinate all of them. So now I have 27 plants in 6-inch pots, scattered all over the house, because there was nowhere to put them where they would all fit.