Ever seen blue balls on a bee? Possibly not what you think, but they do get them.
Bee blue-balls is more accurately bee blue-baskets (on their legs as you can see) and quite the happy condition from a rare forage date. I mean, those baskets are full of sperm. But still...um, let's explain from the beginning.
You surely know pollen is yellow because each spring your car is possibly dusted in yellow by the trees just crop-dusting every surface in their male-junk. Naughty trees… as I’ve heard it put- “they like to go next-door and ‘meet the neighbors’.” I meet my neighbors at the mailbox or while in my garden, so not sure about some of this neighborliness out there. Point is- wind pollinated plants cover the landscape in their pollen and it’s yellow. Or lacking those naughty conifer trees, maybe you recall tucking your sniffer into a flower and seeing the yellow bits maybe even gotten a dusting of gold on your snout. So, pollen is yellow, according to that data collection.
Pollen color is similar to flower color
And yet, there are all sorts of colors that pollen can be. A spectral analysis of 67 flowering plant species’ pollen (kinda small but a start) showed that 75% are either yellow or white as visible to humans. So the majority of their studied pollen is indeed yellow or whiteish to our eyes. But there are plenty of exceptions. With the huge variety of flowers out there, there are many reasons for different colors of their pollen. Some plants actually evolved to sort of hide their pollen, probably because visiting & hungry pollinators or just floral-robbers (not even bothering to help pollinate a bit) will take too much pollen just to eat; not every bee or beetle or fly visiting a flower is actually pollinating them and that certainly is not their actual goal. "Pollination just happens", as a side effect of insect activity, not conscious effort. Pollinators pollinate (and floral-robbers rob) for food, from both pollen and the nectar deeper in the flower. Sometimes the flower/plant has to sneak the pollen onto its desirable pollinator, not feed all the babies of slacker-pollinators or a pollen-stealer.
Pretend the pollen grains are cheese-puffs and you'll get the gist for the bees and such.
Pollen is an enclosed tiny 1/2 plant with only half the normal
number of plant genes (rather chromosomes) and they are meant to grow down into the female flower part- a pistil- to find its eggs to make a full new plant with all the needed genes. It's basically a tiny sperm-bearing half-plant (Scrabble word- "gametophyte"), a way to protect and move the sperm cells to the eggs. Yes, spermS, meaning 2. But let's not get too plant kinky or pollenographic; back to the blue bee balls.
Mostly they're yellow balls.
The sperm is clear.
Most flower pollen are what you probably know- shades of yellow, from basically white to deep oranges. But… like… why? Or in Biologist words- “how?” It is one hypothesis that most pollen is a yellow hue due to flavonoids that serve as a sort of UV protection for the delicate sperm inside. Can’t have the harsh sun’s UV radiation mutating the sperm’s DNA and getting weirdo plant-babies with ears instead of leaves, or something more plausible.
Pollen color is similar to flower color in that wind-pollinated flowers also have yellow pollen and non-colorful flowers because they still need sunscreen for their sperm that flies free in the breeze, but they don’t attract any pollinators to move it around so no flashy petals.
Adding to the theory, SOME night-blooming flowers have white pollen, lacking any flavonoids, not needing sunscreen in moonlight, ya know.
But some are also yellow and there are also a lot of flowers with white pollen that bloom in the bright light of day, so… more study needed! Who needs a PhD project? Perhaps the while pollen is on stamen that stay deeper in the flower, more protected. Who wants to fund a very pretty fun new research project for me?!? Did some species with yellow pollen that bloom at night now become nocturnal after already gaining the sunscreen for their pollen in an ancestor and just haven’t lost that trait? I so would like to build this pollen color phylogeny.
Speaking of plant relations, several species among the Polemoniaceae family across a few genera have blue pollen as well as Geranium genus (including Geranium pratense, G. sanguineum, & G. maculatum), Phacelia tanacetafolia, chicory (Cichorium intybus), Caryopteris clandonensis, Siberian squill (Scilla siberica), Flanders/common poppy (Papaver rhoeas) though very dark pollen, bridges brodiaea (Triteleia bridgesii), and more. Several of these flowers are themselves blue in the petals with matching blue pollen but some have other color petals. Cilantro aka coriander (Coriandrum sativum) is another pollen-provider of unusual color with pink pollen. Pink bee-balls, too cute.
The bees I've seen with the blue pollen baskets were visiting gilia flowers (Gilia capitata, blue thimble-flower). If you spot them in other areas it could be from any blue-pollen producing flower that creates a large load of flowers at that time.
So why/how blue? Pollen color is also effected by the usual plant color pigments despite yellows coming from some times from flavonoids, they can also have carotenoids (the orange of carrots) as seen in sunflower's yellow pollen. And also as usual, blue is coming from anthocyanin (see Blue Thou Art, rare flower color post). At least one paper of a New Zealand fuchsia tree (Fuchsia excortica) with dark bluish-purple pollen found 4 anthocyanins (which are a type of flavonoid) plus several flavonol glycosides (we won’t try to spell those here). Interestingly, among the chemistry jargon, one of the anthocyanins found in this pollen was also identified from grapes (purple ones, I would guess)- p-coumaroyl anthocyanin.
Anyway, with two sperm cells inside, a pollen grain is rich in proteins aka amino-acids, providing the meat row of a bee’s food pyramid. A highly pixelated pyramid, of 2 rows. The other row is their needed carbohydrates from that sweet sweet sugary nectar seeped out of the inside base of the flower to encourage pollinators to get their pollen-transporting little faces or bodies all the way in there. Pollen snack on the way to a sugary reward, and hopefully moving some pollen around from flower to flower but collecting a bunch to bring home for the baby brood as well. That is how a pollinator do. And how, from visiting anthycyanin-tinted blue-pollen'ed flowers, they can get those pretty little blue balls on their way home.