This simple botanical term has a very simple definition: a monocarpic plant is one that flowers once in its life, and after that, dies (the term semelparous means virtually the same thing except that this term is broader and applies to the animal kingdom as well). But when looking at the life of some of these monocarpic plants, or of some of the polycarpic plants (ones that flower multiple times during their lifespan and keep on growing before they die- the vast majority of flowering plants fit this definition) that have 'monocarpic tendencies', the idea of monocarpism becomes a whole lot more complicated.
There are a LOT of monocarpic plants, though my experiences lie mostly with the more unusual or tropical plants that fit this definition (mostly monocots), than of the much more common monocarpic plants most gardeners are familiar with. Just to run some of those more common plants by the reader to familiarize them with such plants: bananas, wheat, sunflowers, thistles, alyssum, asters, zinnias etc. Many of the plants I am more interested in are monocarpic as well- the Agaves and many of its relatives, many bromeliads, some palms, some succulents, bamboo etc.
Ensente ventricosum 'Maurelii' (false red banana) left, and Musa 'Ice Cream' bananas (right) are good examples of monocarpic fruiting plants... these grow for years, but when the flower, they die (always) right after
Above are typical monocarpic grains: upper left is Rye (Secale- photo by olmpiad); upper right Wheat (Triticum- photo by robos); lower left Corn (Zea mays- photo by Famerdill) and lower right Barley (Hordeum- photo by Xenomorf)
Some of the most well known and spectacular monocarpic plants are the Agaves (Agave bovicornuta on left, showing one at the end of its life and another still waiting to flower some year); right is another spectacular bloomer, Agave attenuata, familiar probably to most anyone who lives in southern California where they are planted all over the place
Sunflower (Helianthus annuus)- a very common monocarpic plant (left) photo by Xenomorf ; right is a Thistle in my garden (aka a weed), another very common monocarpic plant
left is a photo of a Zinnia elegans (photo by Kell), another common recognized monocarpic plant; right is an artichoke, another monocarpic plant
Alcantara imperialis left, really nice, large bromeliads that sadly die after flowering; right is a relatively commonly grown palm, Arenga engleri, which is considered monocarpic though since it is a suckering palm, only the flowering stem dies (so is this really a monocarpic plant?)
left is a very large bamboo (Dendrocalamus gigantea) which may live on for over 100 years, but eventually it will flower and die; right is a commonly grown succulent, Kalanchoe luciae, which also dies after flowering, though often lives on in the form of offsets (true monocarpic plant?)
Monocarpic plants are often divided up into life span groups: annuals, biennials and perenials. Most of my favorite plants fit the perenial category (hard for me to get super excited a plant that's only around a year or so). Some people may be tempted to confuse the terms annual and monocarpic, even though many plants are both. Annuals live and die based soley on time of year... some germinate in spring and die in the fall when it gets cold... others germinate in the fall, sort of 'meditate over winter, and then live to summer and die then. But many of these annuals grow their entire season whether they flower or not (most flower) and some flower repeatedly .... if that is the case, they are certainly not all monocarpic.
Two winter annuals (monocarpic or not?): Lamium sp (aka Deadnettle) left - photo Wikipedia; and right, Chickweek (Stellaria media)- photo by timmijo
The carrot is a biennial plant, and seems to be monocarpic as well (flowers once, then dies... eventually)- photo Wikipedia; Right is one of very favorite biennial monocarpic plants, Echium wildprettii (aka Tower of Jewels)... first year grows a nice fuzzy rosette of leaves, then its second year puts all its energy into this huge, incredible, colorful, tall flower... then sadly, after producing a gazillion seeds, dies.
According to the definition, a monocarpic plant flowers only once (mono), then makes fruit (carpic), and then dies... no more growth occurs after flowering. Biochemically, these plants produce some sort of hormonal like substance that makes the plant direct all its energies away from growing foliage and other non-reproductive plant material, all towards the reproduction phase- eg. a flower (or flowers). Once it flowers, and if pollinated (by itself if monoecious, or by another if dioecious), fruit will form and from the fruit come the seeds, taking up the last bit of energy the plant has to give. Evolutionarily this seems a bit of a risk, but it obviously works or these plants would go extinct quickly.
These Hesperoyuccas seen in flower are natives on my property, too (right photo), and they flower spectacularly, make a bunch of seeds, and then die... still they make suckers as well to ensure they do not die in vain.
Well, as it turns out many of these monocarpic plants have other strategies for passing on their genes aside from 'putting all their eggs in one basket' so to speak. Some produce bulbils, or small plantlets on their flower stalks. And some (many, actually) produce suckers or offsets from their root stock/rhizomes. Some even flower repeatedly, though often from root stock or from another location on the plant that is NOT the apical meristem. And still others produce branches that continue on growing leaving only the flowering branch to die. All of these instances put a slight wrinkle into the orginal definition of monocarpism.
These two Agaves in my yard flowered (left is Agave vilmoriniana and right is Agave gypsophila) and on their flower stalk they produced a load of bulbils, or basically baby plants... so this is how these sorts of agaves live on (though the latter species also makes suckers adding another level of insurance its genes will remain in the population)
This spectacular Frucraea macdougallii (left) has finally flowered after 15 years at this botanical garden, sending up a huge flower as its last gasp, but then all these bulbils (right) form (thousands of them) and litter the ground later on... hoping that at least one or two will root and pass on its genes.
Aechmea blanchetiana suckering so that when it flowers, it will still be able to pass on progeny should it be unsuccessful at germinating any seed (left); right is a desert-like bromeliad, Bromelia balansae, showing lots of ripening fruits... but it, too, is making a lot of offsets (seen around each plant) as a 'back up plan'... so once these bromeliads die... they still are not dead as the offsets from their roots live on. Still truly monocarpic?
From a distance it looks like this is the end for this Agave americana marginata (left) since once it flowers it dies... but up close you can see it has dozens of 'babies' already growing ensuring it will live on should a squirrel or bird eat all of its seeds.
These two large populations of monocarpic plants (Aeonium hybrids) are in full flower so one would expect to see must a bunch of dead plants in a month... yet if you come back in a month it looks as if nothing has died or is missing. that is because these plants make LOTs of offsets and sometimes only the main flowering branch dies... so if you clean up the corpses, it looks as if nothing died at all.... still truly monocarpic?
Caryotas, or Fishtail palms, are monocarpic... when they flower they die soon after. You can see from the plant on the left that its foliage is nearly gone but it at least is going out with a bang, producing literally thousands of seeds. This palm on the right is also a Caryota (mitis), but it is a suckering species, so only the flowering stems die, and the rest of the plant continues to live on, making new suckers as the older ones die off... truly monocarpic?
Yucca brevifolia (aka the Joshua Tree) the signiture plant of the Mojave Desert, is a long lived plant (hundreds of years) yet each time it flowers, that branch stops growing (best seen in photo on right with a new flower on one branch, and a dead flower on another, basically ending the growth progress of these two branches.. at least in the exact same direction), but a new branch forms, often growing in a different direction, and life goes on... the plant overall hardly skips a beat.
The bulbil producers can be excused in a way as their offspring are sort of 'pre-started seeds' and still the plant dies afterwards as its supposed to. But the suckering plants are a bit of a different case. Aren't these suckers part of the original plant? Admittedly, in most cases, one could remove the suckers without hurting the mother plant, so these offsets, it could be argued, are now their own plant and do not have to die for the definition to still fit. The mother plant still evenually dies (not right away sometimes...in fact, often not for years to come). These plants do not, however, grow anything more from that used up meristem or growth center that did the flowering- no more flowers certainly and not even any more leaves. But they do continue to grow in a way because their roots and rhizomes are part of the original plant yet continue to grow on and on. In some cases, these offsets are so closely associated with the mother plant that is very hard to tell them apart from it. One large clump forms and from this clump more flowers arise, often year after year, or even multiple times a year, with the clump not apparently changing much. Usually the mother plant dries up and dies and it is obvious that 'life' is over. But in many plants this death is very delayed and often goes unnoticed giving the impression that the plant as a whole is polycarpic. Indeed many of the genera belonging to the family Agavaceae and related family, Aspergaceae, are considered polycarpic even though their lives are a series of flowering events and deaths, with subsequent flowerings always from a different growth center or rosette of leaves, sometimes that is nearly impossible to tell from the original. Below are some examples of plants that have a monocarpic flowering event, but live on in the form of offsets/suckers.
And sometimes these orginal plants not only produce offsets, but a second or third sets of flowers, albeit from root stock rather than the original growth center... but obviously NOT from the offsets (as many do not have any.. or any yet)- so some of these monocarpic plants flower multiple times (sort of goes against the definition). A great example of this occured in my own yard, with my Agave mitis var NOVA. It was a beautiful plant I purchased only three years earlier, and was hoping it would go on living for many years... But alas, it flowered one year, to my dismay- such a short, uneventful life I thought (not a very long-lived agave sadly, despite its relatively large size and incredible beauty). So I was a bit surpised to see it still alive and basically intact the following year after flowering. It did not grow any more leaves, or change in any way that I could tell, but it certainly was not dead... yet. Then, to my surprise, it produced three more sets of flowers over the following 2 years that appeared out of the ground all around the plant. No offsets could be seen. These flowers, though much less impressive, were still on stalks a good four to five feet tall and had plenty of flowers (not noticed if any seed were produced). Eventually the plant started to look the worse for wear after three years, and numerous offsets could be seen, so I got tired of it and dug it up... no idea how much longer it would have survived, or if it would have kept on producing flower stalks from its roots.. but I felt this was indeed a bit of a stretch of the monocarpic definition... at least the above original definition. Perhaps there needs to be a more 'accurate' or inclusive definition of this term monocarpic?
Shots of my Agave mitis 'Nova' blooming in my garden
This is nearly three years later and plant is still alive, though not grown a single leaf from the original apical meristem... but as you can see, new flowers (this is the third set) arise from the ground around this plant... really 'testing' the definition of monocarpism to its limits.
Eventually I dug up the plant, as it was beginning to look weather beaten (still not dead), and discovered it had not only flowered 4 times in the last 3 years, but had (finally) produced a lot of offsets (good thing as I am not sure it ever made any viable seed) ... so this plant continues to live on to this day in the form of multiple suckers
Then there is the situation with the branching species that are 'polycarpic/monocarpic'... ? Some of the Agavaceae, Nolinacea, Asparagacea and Arecaceae (Palms) are tall, branching plants that flower year after year and continue on living many decades (if not centuries for some species). Some scientifically minded say all Agavaceae are monocarpic despite this apparent polycarpic lifestyle, and change the definition of what monocarpic actually means. Many plants that appear to be truly polycarpic have been moved out of Agavaceae and into other related families, such as Asparagaceae (which still has its share of monocarpic plants), such as the Dracaenas, Cordylines, Nolinas, Beaucarneas etc. The arguement, however, made by some, is that these plants are still growing in a 'monocarpic' fashion. 'Monocarpic fashion' is a phrase I sort of made up, but I dont' know how else to describe these plants.
Beaucarneas (like the old, majestic Beaucarnea strictas above) are considered by most biologists to be polycarpic, as they flower over and over again and live for many years... but being an Agave relative, other biologists still consider these plants monocarpic in the true sense that the apical meristem dies after flowering, and though the plant lives on, that growth center is done once it flowers (left); right are a group of Beschornerias, another Agave relative the flowers spectacularly yearly and keeps one going (hence polycarpic... right?)- but the argument is that these plants develop a new growth center after every flowering event, and the plants gradually widen with each new growth center... though the old 'plant' does not seem to die, it does probably stop growing... does that make it monocarpic?
Dracaena draco (aka Dragon Tree) is an Agave relative that seems to bloom and continue on growing uninteruptedly (left); Dracaena rockii, a Hawaiian native species, is seen blooming here as it has yearly for decades... polycarpic plants? ... growing in a monocarpic fashion?
As far as the original definition goes, these plants mentioned above are polycarpic- they flower multiple times. They do not die after flowering, and many do not even fall back on the offset/suckering way of getting out of truly dying as some other monocarpic plants do. But what is actually going on at these plant's growth centers does sort of fit the monocarpic principle: after flowering, the meristem or growth center of any section of these plants (eg. at the end of a branch) does indeed no longer grow once it makes a flower/fruits, even though the rest of the plant continues on growing for many years, making more flowers and fruits and acting like a polycarpic species. Even the Yuccas that appear to grow as one tall, uninterupted trunking species up to some thirty or forty feet in the air, flowering spectacularly year after year, some argue are still showing 'monocarpic growth'. What these people argue, and frankly I cannot say whether they are correct or not... but suspect they might be, is that when these yuccas flower, that growth center does indeed die and will produce nor more flowers or fruits or even leaf growth. But then a branch or new growth center takes over with a new meristem forming, and continues the life of the yucca. What appears to be one solid, straight, uninterupted trunk is actually a yearly continution of linear branching that one could identify microscopically as a series of new growth centers, even though macroscopically it appears to be one solid trunk or branch. Maybe this is the case. But I say that does not make the plant itself a monocarpic species as some of these 'nit pickers' say it does. I prefer to say these tree Yuccas are polycarpic but grow in such a way that fits a 'monocarpic growth pattern'. As I said before, I basically made that phrase up. No idea if any botanically trained biologist would agree with that statement.
Many consider the Bromeliads as a whole to be a monocarpic family. Yet the two genera above (Deuterocohnia represented by the plant on the left, D. brevifolia; and Dyckia shown growing in a large mass of plants in photo on right), are bromeliads that bloom year after year and never seem to show any death. I have not seen even the rosettes that flowered die... but I would not be surprised to learn each rosette only flowered once.
Mexican Grass Tree- Dasylirion quadrangulatum (left) flowering as it has for decades; and Australian Grass Tree- Xanthorrhoea resinosa (right) are both polycarpica plants that seem to be growing in a 'monocarpic fashion' though appear from looking at them as if they are growing as single stemmed plants in an uninterrupted way.
These monolithic Yuccas (Yucca filiferas) live on for what seems like well over a century, forming tall, single-stemmed plants that eventually branch, yet they flower yearly long before branching and keep right on growing... surely these are truly polycarpic plants...?
Some of my favorite plants, palms, also fit in this nebulous pseudo-monocarpic growth pattern. Arengas, Caryota mitis and Nannorhops are three relatively hardy and excellent landscape palms for southern California so we are quite familiar with this three genera of plants here. These plants are polycarpic in that they flower 'regularly' and contine to live on for years (some for many many decades) just like the yucca trees do. Each one of these is a branching or suckering palm and after a branch or sucker flowers, it dies in the typical monocarpic fashion... still leaving the remainder of the tree to continue life uninterrupted. So the argument could be made these palms are both polycarpic and monocarpic... sort of muddies the original definition a bit.
Nannorhops (left) and Arenga engleri (right) are both branching, offsetting and monocarpic palms that keep on living for years after flowering, just not flowering more than once from each branch (which actually does die after flowering). So are these monocarpic or polycarpic palms?
So what if you have a monocarpic plant that you do not want to die after it flowers? Can the cycle be stopped? Reportedly (at least I read this in one of the articles about monocarpic plant culture) one can chop off the flower as it's starting to form and this may prevent the whole hormonal change, involving the plant's inevitable suicide by putting all its energy into the flowering and fruiting process, thus saving its energy for continued living and growing. Whether this is actually true I do not know. Plants that I have chopped off their flowers as they appear do not seem to divert their energies as I would have hoped and still end up dying even without a flower... but maybe I just jumped in too late? If they survived, would they continue on to flower again continuing their suicidal attempts to throw their lives away just for some future spectacular flowering event and send a gazillion seeds into the world, hoping to pass on its genetics that way?
Anyway, my point, after all these photos and rambling ideas, is what exactly does it mean to mean to be monocarpic? Do we need a new definition, or just a new phrase as I have suggested?