One of the fundamental problems long-lived plants have to solve is where to propagate themselves. When is not as much of a problem -- you live a long time; if you don't reproduce this year, well, there's always next -- and both why and how are pretty much decided for you already: it's going to be a seed,1 and you do it or else your whole species is going to go extinct. But where?
If you just let the seeds drop, your next generation is in a decent spot -- you know this because you have managed to live there for however long it's been. However, this also means that your children are going to be competing with you for water and minerals, and you're likely to shade them so much that they won't be able to get any light, and will struggle to get going at first, which will lead some of them to early deaths. Or maybe they'll outcompete you and lead to your early death. Either way, not terribly appealing.
You could set your seeds free to float on the wind, or drop them into a body of water, to float around until they hit a suitable spot: this ensures that at least some of them will wind up far enough away from you that they're not going to compete with you. However, most wind-borne seeds will land in places where they can't grow (too salty, too wet, too rocky, too dry, etc.), and water-borne seeds are mainly going to travel in a single direction -- either around the edge of the lake or downstream. Water travel is nice in that you know that there will be water waiting for the seeds when they get wherever they're going, but it's also very limiting, in terms of total land space: sooner or later, you're trying to drop seeds around the same lake shore that your relatives are already circling, or down the same stream that's nothing but root-to-root you up and down the banks already.
Two varieties of Persea americana fruit: the black one is I think a Hass; the green is a "Slimcado," a variety that's supposed to have 1/3 less fat than . . . something. I don't think the sticker actually said what it has 1/3 less fat than.
Finally, you can take advantage of something more mobile than yourself, which is what the avocado (
Persea americana) decided to do. The fruits are calorie-rich, so anything that can eat them
2 gets a good reward for doing so. They even fall off the tree before they're ripe and then ripen on the ground, which is more convenient if your seed distributor doesn't climb. And the seed is (relatively) huge, hard, and rounded, so it easily survives passage through a large animal's gastrointestinal tract, which as a bonus means that the seed starts its life in a moist, nutrient-rich pile of dung.
If you're an avocado, then, it would seem that you have life all figured out, and you can just lay back and enjoy the rewards of your cleverness while your partner distributes your seeds for you. Right?
Well, you
could, if only you hadn't picked this guy to be your seed-carrier:
That's a ground sloth,
3 and they went extinct in North and South America about 10,000 years ago, give or take.
4 But that's okay, 'cause you've got a back-up:
Photo by Leonard G., from Wikipedia.
Oh, shit.
That's a gomphothere, the New World answer to the elephant,
5 which also started to go extinct around 10,000 years ago,
6 though the gomphotheres stuck it out quite a while longer -- possibly lasting until as recently as 6000 years ago.
As far as I know, there is no hard evidence to show that either of these animals was
definitely the distributor of
Persea seeds, but there aren't a lot of candidates: whatever distributed avocados had to be a pretty big animal, because all indications are that they're supposed to be swallowed whole. There are only so many animals big enough to do that at the right spot in the fossil record. It's an educated guess.
Whatever it was, if not the sloths or the gomphotheres, went just as extinct as they did, so the central point remains unchanged. So the widow part of the "person" for this plant is because
Persea has lost an animal partner, so to speak. The reason why he's a widow
er, and not a widow, is because the Nahuatl people of Mexico, who stepped in to take the gomphotheres' and sloths' place,
7 chose the name for the plant that wound up sticking:
ahuacatl, which means, in the Nahuatl language, "testicle."
8
Fruits on a tree outdoors. Photo by B.navez, via Wikipedia.
No two sources agree on exactly where or when human domestication of the avocado first began, but Wikipedia says the first evidence of avocado use dates to 10,000 BC, and organized human domestication began roughly 8000-9000 years ago. There's also some confusion about the geographic origin of the species, with some sources putting the original range from Central America north to the Rio Grande River and south to Peru, and Wikipedia locating it specifically in the state of Puebla, Mexico. I'm not going to go into the history of avocado cultivation or the peculiarities of cross-pollinating avocados or any of that, nor am I going to talk about how wonderful and delicious they are,
9 or how nutritious, or how easy to grow outdoors, or any of that, because dammit, this is a houseplant blog and we have to get to the houseplant stuff.
I suspect that most indoor gardeners eventually wind up trying to grow an avocado from seed. Seeds are easy to get, and easy to sprout, so it's sort of a logical thing to try.
Nobody, as a result, tries to
sell them as houseplants, though I have my suspicions that a clever enough marketer could probably pull it off: the leaves are a nice, slightly metallic green, and they're not particularly difficult to grow. A new name, maybe a slightly dwarfed habit (either a small-statured variety or a regular variety that's been chemically dwarfed), some kind of made-up legend about them being lucky,
10 and I think a grower could have a hit. The only thing that keeps them from being grown more indoors, I think, is that indoor-grown plants tend not to look that great. But mass-production in Florida and proper pruning of the young plants would take care of that problem, too. I really do think there's money in this idea somewhere.
PROPAGATION: The usual way one starts an avocado is, one removes the seed from the center of a supermarket-bought fruit, washes it off in running water (no soap), suspends it pointed-end-up with toothpicks over a glass of water, puts the whole thing in a warm, sunny spot, and waits for it to split open and begin to sprout.
Seeds suspended in water with toothpicks. Photo by KVDP, from Wikipedia.
This method is fairly straightforward, though there are ways to do it wrong. You should change the water regularly, lest the seed start to rot. Opinions differ on exactly
how often to change the water: I'm inclined to say at least once a week, though some sources say once every few weeks. More often is better than less often. You should also maintain the water level more or less constant at about halfway up the seed: don't submerge it completely, and don't let all the water evaporate so the seed dries out.
But you don't have to do it like that. You can also start it directly in soil. If it's decent soil and you keep it moist (
not waterlogged: moist) for long enough, in a warm, sunny spot, just under the surface of the soil, that's supposed to work just as well. I've started one in soil before, but that sort of doesn't count: the seed had already sprouted while in the fruit. (I don't know why I didn't get a picture. Sorry.)
Either way, as long as the seeds never dry out, germination is usually pretty reliable. If I remember correctly, although the online advice is usually to wait 4-6 weeks before the sprout emerges, the one we started in water was much faster than that. And the second one didn't even wait on us to take it out of the fruit.
LIGHT: Well, the websites all say that you should give your plant as much light as you can, up to and including full sun, but the plant doesn't necessarily
have to have that much: my personal plants get some sun for a few weeks in the summer, but only bright indirect light the rest of the year, and they've done fine. They're not gorgeous, and they might grow faster if they were getting more light, but the point is that they're not that particular about how much direct sun they get, so long as the light they're getting is bright.
Plants grown under lights may grow fast enough to run into the lights, which can bleach and burn the developing younger leaves, causing them to fall off. Keep some distance between artificial light and the top of your plant.
The better of my two plants, at about 11 months old.
WATER: The usual on-line advice is to keep them from ever getting really
dry, but not so much that they get sopping wet either. My avocados dried out much more slowly than I was expecting when first potted up a year ago, but lately they're needing water every couple weeks. I don't feel like they're particularly fussy about when they get water, so long as I water thoroughly.
One site said that the leaves of plants which are too wet will curl under, while plants that are too dry will drop leaves. I've never seen either behavior on my plants, and it's not like I'm super-consistent with the watering, so I'm not sure I believe any of this. I have seen curled leaves on other people's plants, but I'm not convinced that this means they're too wet. (I guess if you suspect that the plant's too wet already, this might count as confirmation.)
HUMIDITY: The usual advice is to do something to boost the humidity near the plant as much as possible. I can't say my plants have ever complained about the humidity in here, but then, the humidity here is rarely all that low. If air is too dry, you may get tip burn or dropped lower leaves, though tip burn can also be caused by mineral build-up in the soil, and occasional leaf drop on an older plant is normal.
TEMPERATURE: There's a lot of debate on-line about whether or not established avocado trees, outdoors, can take a freeze or not, but I'm hoping that figuring out who's right isn't important if you're growing an avocado as a houseplant.
PESTS: Nothing in particular. I haven't had any spider mite problems on my plants, and spider mites are the pests I'd have if I were going to have pests.
11 Persea species are especially susceptible to a particular mite called the persea mite, but unless you live in an area where avocados are grown outdoors, persea mites aren't likely to be a problem on your plant.
The outdoor growers seem most concerned about beetles, caterpillars, and weevils, none of which are likely to be an issue inside either. Fungal diseases are more of a concern (especially if you're misting to keep humidity up, or if you water from overhead in a shower or something, like I do), and scale and mealybugs are always something to watch out for.
GROOMING: The recommendation for pruning young avocado plants is usually to wait until a stem gets about 6 inches (15 cm) long, then cut it back to 3 inches (8 cm), over and over, until the plant has branched out well. I have a hard time doing this to plants, even when I know they need it,
12 which is one problem, but the other problem is that the plants aren't always co-operative even when you do cut them back. This one, after getting cut back, grew one humongous leaf and one medium-sized leaf, didn't branch, and then stopped doing anything at all for several months:
My stubborn non-branching plant.
You'll also want to check your plant regularly to see whether it needs to be repotted:
Persea doesn't like to be cramped. There seems to be general consensus that you shouldn't repot an avocado in the winter; if you can, wait until spring instead.
You're also not likely to get fruit on a plant grown indoors, though it happens occasionally on older plants, especially if they get to summer outdoors. If you
do get fruit, it won't be the same kind of fruit you originally purchased.
FEEDING: Feed with a regular houseplant fertilizer at quarter-strength with every watering, or feed every three months at full-strength. The former method is more hassle for you, but probably better for the plant. Older, established plants may need more fertilizer than younger plants of the same size.
Persea is sensitive to mineral buildup and overfertilization; either can result in burnt leaf tips. (Tip burn is also a sign of low humidity, though.) Flushing the pot with a lot of distilled water or rainwater is one way to deal with this; you could also remove as much soil as possible from the roots and replace it with new soil, though that's more traumatic for the plant.
One of my references, the New World Encyclopedia, had this to say about the avocado:
There is an important interdependency between avocados and people. The plant lacks a seed dispersal technique outside of humans. It is hypothesized that it originally co-evolved with large mammals that are now extinct, such as the giant ground sloth, with these ecological partners vital to seed dispersal. New mechanisms have not evolved, but the effectiveness of human intervention has allowed the plant to prosper. Of course, in exchange for this benefit, the avocado provides a nutritional and desirable fruit for people.
This bugs me, because of course a new dispersal mechanism sure as hell
has evolved, and we're it. We don't eat the fruit whole and then pass them in our . . . er, "dung," true, but
Persea americana doesn't produce the same kind of fruit it used to, either. It's shuffled its genetics around and come up with a different fruit than what existed in the past, and if you don't believe me check this out:
"Criollo" avocados, the fruit of uncultivated Persea americana. Photo by Nick Saum, www.nicksaumphotography.com. Released under the GNU Free Documentation License (CC-BY-SA-3.0). Via Wikipedia.
Sure, we had a more direct and deliberate hand in the reshuffling than the sloths did, breeding them purposely to get the traits we wanted, but it's still evolution. We are part of the environment of the avocado plant, and it's changed to reproduce itself better in this new, slothless environment. Change in successive generations of an organism, over long periods of time, is what evolution
is.
This also means, to extend my earlier metaphor, that the once-widowed avocado has remarried, and we're the bride. I hope this works out better for
Persea than its previous marriages did.
References in no particular order:
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Photo credits: Mine unless otherwise identified in the text.
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