Every single cactus flowers, and thus of course blooms. While this is not all that unusual to discover, what might be a bit perplexing learning there’s a sub-section of cacti that actually only bloom at night.
These night-blooming cacti collectively have come to be known colloquially as “Night Blooming Cereus,” which as Wikipedia defines it, “is the common name referring to a large number of flowering ceroid cacti that bloom at night.”
Certainly not all cacti have night-time blooms. Most cacti – actually the vast majority – have flowers that bloom during the day. But daytime bloomers don’t seem quite as strange, and feel a lot less confusing since they don’t appear to us very different from the everyday flowering plant.
Night-blooming cacti? They feel unique because opening up a flower at night exclusively seems pretty darn odd and – to an extent – counterproductive.
Flowers exist to help a plant reproduce. Most of us get this on a certain level, though maybe not in-depth.
Flowers can help plants reproduce in a few different ways. The most common: flowers contain pollen, which contains the male sperm cells of the plant within it.
Flowers attract pollinators – animals or insects which transfer pollen from one plant to the next. As the pollinators move from plant to plant, pollen attaches itself to their body parts – feet, bellies, mouths, etc., then the sperm cells hitch a ride to every other plant they visit, thus helping them spread.
Ideally, of course, and as frequently happens if there are multiple plants of the same kind in the vicinity, the sperm-containing pollen that’s hitched a ride helps all the plants-of-the-same kind in the area become fertilized.
The reason fertilization is important? Again, Wikipedia to the rescue: “After fertilization, the ovary of the flower develops into fruit containing seeds.”
So to develop seeds, many of the plants in need not only to flower, but to attract pollinators to their flowers so those pollinators can transfer the male sperm cells contained within one plant’s pollen to other plants of the same kind, and receive those sperm cells contained in other plants’ pollen as well.
Again, this likely makes sense to you already, as even if you couldn’t explain the role of flowers in the reproduction of a plant, you likely already had an inkling or a general gist of how it worked without having the full picture in mind.
Now back to those night-blooming cacti – because they seem pretty darn strange flowering at night when everything else on the planet seems to do extremely well attracting pollinators in the morning.
You’ve seen the bees. You’ve seen the lady bugs and butterflies, as well as the birds munching away in the best and brightest hours of the morning. Why the heck would cacti be wasting their time blooming at night?
I’m going to be honest, I did some digging and I couldn’t find reputable sources like I wanted talking about night-time blooming cacti specifically enough to have a concrete answer on the topic. But there are a couple reasonable explanations individuals have brought up and I think they might be right in how they explain why some cacti bloom at night.
I’m not saying either is correct. It might turn out neither theory is true – or that both are, or even that just one is the true answer. But they seem reasonable so here the explanations are. Starting with the most likely (in my opinion)…
2 Possible Explanations for Why Some Types of Cactus Bloom at Night
Theory 1: Night-Blooming Cactus Pollinators Are Nocturnal
Pollinators across the globe come in many different shapes and sizes:
Insect pollinators include bees, (honey bees, solitary species, bumblebees); pollen wasps (Masarinae); ants; flies including bee flies, hoverflies and mosquitoes; lepidopterans, both butterflies and moths; and flower beetles. Vertebrates, mainly bats and birds, but also some non-bat mammals (monkeys, lemurs, possums, rodents) and some lizards pollinate certain plants. Among the pollinating birds are hummingbirds, honeyeaters and sunbirds with long beaks; they pollinate a number of deep-throated flowers. Humans may also carry out artificial pollination.
While the majority of flowers on the planet earth are pollinated during the day, there are insects and other animals on that list that are nocturnal. These include bats and most moths. Some ants are nocturnal, as well as some lizards – sound like the type of insects and animals you can find in deserts? It does to me.
The best guess I’ve found as to why some cacti only bloom at night is due to the fact that there are nocturnal pollinators out there – so maybe these night-blooming cactus plants are blooming specifically at night because their pollinators happen to be awake and active, getting busy and doing their feeding at night rather than during the day.
Sure, bees are out during the day, but in the desert, you’ll get more moths than bees hands down. And moths are usually nocturnal, though there are moths that aren’t.
Some sources actually go so far as to list moths as the Night Blooming Cereus Peruvianus major pollinator: “The bloom will only open at night and is pollinated by a moth.”
Another source lists moths and bats as common pollinators of Night Blooming Cereus:
All these flowers have a large, white bloom that only opens at night, so they cannot be pollinated by the usual daytime pollinators, like bees. Because these flowers open at night, nocturnal creatures, such as moths and bats, are responsible for pollinating night blooming cereus.
That seems like a good enough explanation to me, though there’s one other that I think explains well why these cacti don’t bother to bloom all day long, and may be a factor in why they bloom at night instead of in the day.
Theory 2: Flowering Requires Water & Less Water Loss Happens at Night
In deserts where cacti grow, water is scarce and the weather is quite hot.
The flowering process requires water – a lot of a resource that cacti are already typically very low on due to their environment.
As a result, it may be that night-blooming cacti have evolved to bloom at night – at least in part – in order to conserve water.
In arid and dry environments, flowers may dry out faster if they’re exposed to the hot sun than if they open and bloom at night. This may have led some cacti to evolve to bloom only at night in order to reduce the amount of evaporation that happens, and thus reduce the overall water reserves necessary to deplete in order for them to have their flowers bloom.
This is one theory at least. Another? Blooming requires a lot of water, and since the pollinators of Night Blooming Cereus may be out only, or in majority, at night, these cacti have evolved to bloom only during the hours they’re most likely to be pollinated, thus saving water in not blooming during all hours of the day and night.
That’s how the theory goes at least! Whether it’s right is up to scientists to discover.
Your Thoughts on Why Some Cacti Bloom at Night?
Why do you think some cacti bloom at night? Do you think the explanation is one of the theories I’ve mentioned? Both in combination? Neither?
Do you have any thoughts or information that could help expand on the theories I’ve listed above? Any extra theories you’ve heard of or thought up on your own?
Would love to hear your thoughts on the topic in the comments down below!