In the regions of the world with icy, cold winters, the only way many people encounter pineapples is in the produce display at the grocery store. This exotic fruit from the tropics is so different from anything you’ll see growing in temperate zones, it can seem a mystery what kind of plant this fruit grows on. I’ve even heard debates over whether pineapple fruits grow on a tree, or underground like a turnip. (Actually, it’s neither.) Here’s the real story on how pineapples grow.
The pineapple plant is in the bromeliad family, along with Spanish Moss, and many of the “air plants” sometimes sold as house plants. Like many of the plants in that family, it grows as a crown of long, straight leaves, all emerging from one central point, similar to the way an aloe or yucca plant grows. The height of a pineapple plant is usually about knee high.
When a pineapple plant is ready to produce a fruit, it sends up a flower stalk from that central point. The flower cluster looks like a little baby pineapple fruit, with a tuft of leaves on top, and the actual pineapple flowers are tiny purple tubes that stick out from the sides of the baby pineapple.
Over a period of months, the stalk grows taller, rising above the leaves, the purple flowers drop off, and the structure swells into a green pineapple. About five months after first emerging as a flower cluster, the fruit then turns from green to yellow/orange, signaling that it’s ripening and ready to harvest and eat.
Commercial growers who ship fruit to markets thousands of miles away usually harvest pineapples while the fruits are still solidly green, to enable time for shipping and sitting on the store shelves. These green-harvested fruits do ripen, but they don’t develop the full sweetness and flavor they’d reach if left on the plant until they start to ripen. So if you really want to experience what a pineapple can taste like, you need to grow your own and let it ripen on the plant, or find a direct to consumer supplier who can harvest already-ripening pineapples and send them to you.
In my area, growing pineapples outdoors, I find it’s best to harvest a pineapple as soon as I see the first bit of yellow color appear at the base of the a fruit, then I let the ripening process continue on my kitchen counter. The reason for this is once the color shift happens, the fruit starts to release that wonderful fruity aroma, and the fragrance attracts wild critters who enjoy eating pineapple as much as we do. If you leave a fruit on the plant until it’s completely colored, very often you’ll come out in the morning to discover big holes have been chewed in your precious fruit. But once a pineapple starts to change color even a little bit from green to yellow/orange, the fruit is within a few days of becoming completely ripe, so you can pick and you’re only losing a few days on the plant, as opposed to many weeks of time on the plant like the commercially grown pineapples that are harvested green.
Some of the most common questions people ask about this plant are: Does a pineapple plant produce fruit just once? What happens to the plant after it produces a fruit? These are questions I wondered myself, and I wasn’t able to find a really clear answer online. But now that I’ve spent a few years observing how pineapple plants grow, I can explain what happens after fruiting.
When a pineapple plant sends up that central stalk with a fruit on top, it also usually makes some side-shoots growing out of that stalk. These can form at any point on the stalk, from just underneath the fruit, down to the very base of the stalk, and anywhere in between. The lower down a side-shoot forms, the bigger it tends to be. Growers have different names for side-shoots, depending on where they form: the big ones that form low down on the stalk are called “suckers”, and the smaller ones that develop higher up are “slips”.
If you leave a pineapple plant in place after harvesting its fruit, the highest side-shoots, the slips, will eventually drop off, and if not planted in the ground, they’ll probably dry up and die. Side shoots that form mid-way up the stalk will usually stay attached, and they can sometimes flower and produce a smaller fruit than the original pineapple which grew at the top of the central stalk. But if any side-shoots form very low down on the stalk, near soil level, those side shoots can grow their own set of roots into the soil, and if that happens that shoot can then grow as big as the original plant was, and can produce another full-size pineapple fruit.
So for a pineapple plant to be able to regenerate itself, it needs to produce side-shoots (suckers) low enough that they can put their own roots into the ground. For the commercial varieties of pineapples I’ve worked with, only a percentage of plants actually do this. In a patch of pineapples, after fruiting, more than half of the plants only produce side-shoots that emerge too high to send their own roots into the ground. And for the plants which do regenerate themselves by making a low side-shoot that roots itself, that often leads to only a single new cycle of growth – once that new crown has fruited, it often fails to produce any low-growing side-shoots.
The result of this growth pattern is that after planting a bed of pineapples, in my observations the best production happens in about the second to third year (Some of the plants produce fruit the second year, some fruit the third year). But after the third year, pretty much every initially planted crown has already fruited, so you’re into fruit produced from side-shoots. (This is called a “ratoon” crop of fruit.) Overall production from the patch declines, and many of the fruits are smaller, because they grew on side-shoots that emerged too low to root themselves into the ground. After a few years, many of the plants have multiple tiers, with side-shoots growing out of side-shoots growing out side-shoots, each new crop a bit smaller than the last.
So commercial growers regularly start new plantings by breaking off suckers from already-fruited plants, and sticking those suckers into fresh soil, where they can grow into full-sized plants, resulting in full-sized fruits a year or two later.
You might be wondering: what about seeds? Before humans came along, nobody was breaking the side-shoots off from spent pineapple plants and sticking them into fresh soil, so how did these plants reproduce? The answer is: ancestral pineapple plants did produce seeds – and modern varieties still can. Unlike bananas, where humans took an original seedy fruit and selected seedless variants, modern commercial pineapple varieties are still capable of producing seed-filled pineapples. And those seeds can grow into new pineapple plants.
For this seed production to happen, a pineapple plant’s flowers must be pollinated by a hummingbird with pollen from a different variety of pineapple flowering at the same time. Without this pollination, pineapples make seedless fruits, which is what happens about 99.9% of the time. When people plant out a bed of pineapples, they usually plant out the whole bed with all the same variety, so even though a bunch of the plants might flower at the same time, genetically they’re all a single clone. But if you plant out different varieties in close proximity, and if those varieties bloom at the same time, and if a hummingbird visits and transfers pollen between varieties, you’ll get pineapples with tiny seeds scattered through the flesh. The seeds are so small you would barely notice them in your mouth when eating the fruit, but they do make the fruits look less appealing (to some eyes at least). For this reason, the US state of Hawaii bans the importation of hummingbirds into the state, so the commercial crops of pineapples there don’t ever end up full of seeds.
Since pineapple plants grow for more than one year, but not indefinitely, I’d classify this species as a short-lived perennial. Many other bromeliad species are better than pineapples at renewing themselves, producing their “suckers” right at ground level, so those new crowns can easily grow their own roots and the plant can continue to grow indefinitely. I wonder if that characteristic was originally present in pineapples, but has been bred out of commercial varieties of this crop. Or maybe the trait never was present in Ananas comosus. If it could be (re)introduced into this species, we could have true perennial pineapples. If you have any knowledge about this, or if you know of pineapple varieties which do have a more perennial growth habit, please leave a comment.