the color Purple

As I look around at flower gardens in my backyard and in my neighborhood, I see a lot of purple.  Where the first flowers of spring seemed to be largely pink in color, the first flowers of summer seem to be mostly purple, a color that is not all that common in plants.  Why so much purple, and why now?

The intensely violet color of spiderwort flowers is on one end of the purple spectrum.

False Indigo flowers are another example of intensely dark purple color.

Purple is for the bees, and especially the solitary bees which are the most abundant and hearty pollinators we see in cool spring and early summer weather, before honeybees and butterflies have become active.  Bee eyes can detect light wavelengths in the ultraviolet part of the spectrum, and it seems that plants have adapted their floral displays to guide the bees right to the places on the flower where their search for nectar or pollen will do the flower the most good (i.e., pollination).

Streaks on the landing platform petal of the iris are probably visible to bees in the ultra-violet range.

One study with bumblebees in Germany showed that naive bees were highly attracted to flowers in the ultra-violet to blue range of wavelengths, and those flowers tended to produce more nectar or nectar with higher sugar concentrations than flowers of other colors.  Purple flowers that attract solitary bees tend to have the highest sugar concentration in their nectar (20-50% sugar), compared to yellow and red hummingbird and butterfly flowers that average around 20-22% sugar in the nectar.

The bell flower petals look homogeneously lilac to our eyes, but what do they look like to bees?

The variation in “purple-ness” of early summer flowers is due to the proportion of anthocyanin pigment in the flower in response to the pH of the soil environment.  In the presence of acid (or hydrogen ion), the pigment is red (or pink), whereas in the presence of nitrogen base the pigment is blue, and in the presence of aluminum, it is violet.   So, you can change the colors of your hydrangea or forget-me-nots by what you put in their soil.

Magenta-colored clematis flowers are the result of a redder expression of anthocyanin in a more acid cellular environment.

Flowers of this penstemon are pink-purple, based on the reaction of the anthocyanin in a more acid pH.

Bachelor’s Buttons, native of Europe, grows best in basic soils, which accounts for its deep blue color, and the bees seem to love it.

Purple is a coveted color in the garden, because of its rarity, and the ephemeral nature of purple flowers.  Looking back in our own history, we find that limited resources and the labor-intensive process used to create the color purple made it an expensive luxury, indulged in only by the most wealthy or by royalty.  Regardless of expense, its calming (blue overtones), yet energizing (red hues) make purple a favorite color.

the nectar thief

Each year, the Ohio Buckeye tree outside my porch window puts out a prodigious number of flower spikes, which reliably attract a few pollinators and one clever nectar thief.

Pollination of these flowers is sufficient for the tree to produce copious quantities of nuts, which are harvested by the squirrels in the fall.

Hummingbirds, bumblebees, and orioles visit the Buckeye tree in the spring, along with a horde of Tennessee warblers.

Tennessee Warblers arrive just as the Buckeye tree is in full flower. How do they manage to time it just right?

Tennessee Warblers really have nothing to do with the state of Tennessee, but do migrate through there, where they were first seen and named way back in 1811.  Like many small insectivores they spend the winter in the tropics, eating insects and nectar, and breed in the Canadian spruce forests where they specialize on spruce budworm and are critical to controlling outbreaks of the moth there.

Though they do visit flowers to consume nectar, they do not perform much of a pollination service for the plants, because they use their sharp beaks to pierce the flower at its base to get at the nectar at the bottom of the flower tube, thus avoiding the pollen on the anthers sticking far out of the flower.

Note where the beak is positioned to the side of the flower at its base. Pollen might inadvertently stick to the bird’s head or breast as it bumps into the anthers, but it might be hit or miss in depositing the pollen on the stigma of another flower.

Their beak is slightly open as if they are biting the flower to open a small hole in its base.

They only visit for a few days each spring, so I guess this must be the peak of their migration through MN this year.  You can see a light dusting of pollen on this bird’s neck and breast.

The sugars in the nectar will be metabolized and stored as fat and should provide these tiny little birds (about 2/3 the size of a chickadee) with the fuel they need to get to the Canadian spruce forest to breed.

(these photos shot with the Sony RX10 iii bridge camera through my porch window — what an amazing little camera!)

Bees and blossoms

Spring is in full swing here in northern California, and I was glad to see so many honeybees out performing their pollinating service.  In fact, there were many more honeybees here than I typically see on the flowers in streetside gardens at home. Hmmmm…wonder what that means?

Honeybees swarmed the tinybflowers of California lilac (Ceanothus species)

They were probably collecting pollen from this plant (rather than nectar).  Look at those full pollen baskets on the rear appendages.

Twin flowers of this mint species offer nectar at the bottom of a deep floral tube, causing the bee to pick up pollen on its back as they brush by the anthers.

Better view of the plant-pollinator geometry that ensures the bee does its job for the flower while getting its reward. Bees typically spent several seconds on each flower, so either the nectar was hard to get to, or there was a lot of it (probably the former).

Bright purple modified leaves at the top of the flower stem attract bees to this fragrant mint. The tiny, purple-black flowers stud the sides of a thick floral stem.

I think this might be Spanish Lavender, which looks nothing like MN lavender.  It’s highly aromatic, like other lavenders, though.

California is experiencing a mega-bloom after all the recent winter rain, so I hope I will see a lot more of these plant-pollinator interactions in the next few days.

the beginning of the end…of summer

It’s down to the asters and goldenrods, among the last of the blooms for pollinators to visit before it’s too cold to visit anything.

A couple of very cold bumblebees must have spent the night in these asters. They were pretty comatose on this chilly morning.

The yellow jacket mimicry of these very large hoverflies was so good, I almost walked away from this Stiff Goldenrod plant to avoid them.

Later in the day, a hoard of bumblebees attacked the few remaining flowering stems of Showy Goldenrod. It’s a last chance to harvest nectar and pollen to store away for the winter.

All this work, and then what happens to these insects?

The bumblebee queen who founded her colony in the spring (the old queen) and all of the workers she produced will likely die in the first freezing weather of the winter.  All their work over the summer and fall was to ensure that new queens would be born and survive the winter to found new colonies the following spring.  New queens hatched during the summer feed voraciously on nectar and pollen in the fall to lay down fat stores that will carry them through the winter in their underground nest.

Dahlias keep producing their glorious blooms well into the fall until the first hard frost, another good source of nutrition for young queens.

Hoverflies (depending on the species) might overwinter as adults or as late-stage, fully grown larvae, by taking shelter in protected nooks and crannies of  tree roots or bark.  In Minnesota, they will have to withstand freezing solid, as temperatures drop well below zero.  Individuals that overwinter as adults (probably females) are the ones we see flying around in the spring looking for aphid-infested plants on which to lay their eggs before they die.  When the larvae hatch, they have a food source waiting for them. A second wave of hoverflies join the party after warmer temperatures have spurred them through the pupal stage to emerge as adults.

Hoverflies slurp up nectar from fall flowers to build up their fat reserves. Some of the fat will be used to produce a glycerol anti-freeze compound so that their cells can tolerate freezing without damage from ice crystal formation.

Pollinators, large and small

The purple flowers are blooming in my garden: spiderwort, weedy creeping charley, iris, bellflower, mountain cornflower, and lovely blue wild indigo. And there are a few bees around, doing their best on the limited amount of nectar and pollen available so early in the summer.

This queen(?) common eastern bumblebee approaching a flower of the false wild indigo is faced with the task of getting to the nectar at the base of the flower through what appears to be closed “doors” (lateral petals) of the flower.  She is really too big to fit.

Her weight is sufficient to separate the wings (lateral petals) of the flower, so she can poke her head (and tongue) deep into the base of the flower where there is nectar.

The two halves of the keel petals at the bottom of the flower also separate under her weight, exposing the anther pollen and the bright, orange-yellow, three-pronged stigma (female receptive surface). Pollen she carries on her legs and body from another flower will stick to the stigma and travel down its tube to fertile ovules in the flower ovary to make seeds.

Pulling away from the flower before flying to the next one, you can see the contact between bee and pollen.

Lady Bumble made the rounds of the newer flowers at the top of the raceme, working her way from oldest at the bottom to newest opened at the top, and then on to a different spike of flowers.  But the small solitary bee working these flowers had an entirely different strategy.

You can see how tiny this little bee is in comparison to the flower.  It preferred visiting the older flowers, whose petals were drooping and not fitting as closely together as in the younger flowers. 

Now, how to get inside the flower to reach the pollen? Squeeze through the tiny crack between petals.

Crawling inside finally, the bee disappears for a few minutes before crawling out and making its way to another, older flower.

Older flowers may not produce much nectar, But smaller bees don’t require as much as large bumblebees anyway. And perhaps pollen collection was of more interest to this tiny bee.

a rare beauty

Lady’s Slipper Orchid may be one of the slowest growing plants in the world, taking 6 to 11 years to reach the size when it first flowers.  But when it does, we rarely fail to notice, and marvel at its color and structure.  All this from a minuscule seed the size of a speck of dust!

I was quite excited when my neighbor showed me the Lady’s Slipper Orchids growing in his back yard.

The name, of course, comes from its shape, the swollen labellum appearing to be a dainty shoe for a pixie-sized lady.

Like many showy flowers, orchids are dependent on pollinators to transfer pollen from one plant to another.  But Lady’s Slippers and another 40 percent of the 20-30,000 orchid species of the world attract their pollinators with color, fragrance, or even by mimicking the shape of a female pollinator of the same species, and offer no nectar reward.  How do they get away with “cheating” their pollinators and still ensuring pollination success?

By “inviting” them in, trapping them momentarily, and then providing a narrow escape route that forces the pollinator to squirm by sticky pollen sacs on the anther as they exit.  Here’s how it works.

It’s a one way route through the flower, in through the enticing, colorful and fragrant labellum, and out through the slit in the back, top of the flower.  When they visit the next Lady’s Slipper flower, they rub the acquired pollen onto that flower’s stigma.  Voila, Pollination!

Bumblebees are too large to fit through the narrow slit at the top of the flower, so they exit the way they came in.  Smaller bees land on the hairy pad at the back of the inside surface of the labellum, crawl toward the light showing at the top, and squeeze themselves through the slit, as shown on the video below.

Practicing this deception seems risky, especially since bees are less prevalent today than they once were.  This rare beauty, once found throughout North America, Europe, and Asia is in decline world-wide.  It suffers from being over-collected, loss of habitat, and now —perhaps, a decline in the numbers of its pollinators.

Mug shots – take 1

It’s great when you can get really close to the wildlife, i.e., right in their “faces”, to grab a “mug shot”.  I didn’t get many this year, but there were a few opportunities, assisted either by my extremely long (600 mm) telephoto lens or my trusty macro, to get up close and personal with the local wildlife on our travels and in my backyard.

Hoverfly gleaning pollen and/or nectar from New England Asters.

American-painted-lady-on fall-blooming Sedum; they came through by the dozens to congregate on late-blooming flowers

Honeybees foraged on New England Aster; I saw more of them this year than in the last 5 years combined.

A tiny carpenter bee feasting on pollen from newly opened anthers on a coneflower.

We found a Bullfrog calling in a desert oasis in Arizona. Kind of ugly, but beautiful eyes…that might be a mosquito on his upper lip trying to get a meal.

A Chuckwalla was sunning itself at the Sonora desert museum in Tucson. Dark pigmented scales on its underside help it soak up heat from rocks. Chuckwallas love to hide in rock crevices and resist being pulled out from their hiding place by puffing up their body with air, expanding into any empty space in the crevice.

Snapping Turtles have large jaws and long necks, but this one was protecting itself by withdrawing into its carapace.  My what beady little eyes you have, Mr. Turtle.

Eye to eye with a Great Blue Heron

Male Mallard Duck before molting a new set of showy feathers

Chickadee with an attitude…

very busy bees

The number of bees in the backyard has quadrupled (or more) since New England Asters and Yellow Oxeye Daisy have begun blooming. On warm days the bumblebees and honeybees swarm over the flowers, probing quickly and moving on.

But on closer inspection, I saw a number of smaller bees that were sharing the pollen and nectar resources as well.

The Common Eastern Bumblebee dwarfs the tiny metallic Green Sweat Bee, but there are so many flowers blooming now, there is little interference from competitors.

With the help of my trusty macro lens, I tried to zoom in on what these tiny bees were doing.

Miniscule Small Carpenter Bees were the perfect size to get their head and tongue into the tiny crevices in the disc flowers of Rudbeckia flowers.

Small Carpenter Bees, like their larger cousins, are good at chewing their way into plant stems, constructing nesting chambers in the central pith for their larvae.

A Dark Sweat Bee and an unidentified, slightly out of focus bee with very long antennae and a very fuzzy thorax shared one flower head.

Sweat Bees were supposedly named for their attraction to moist, salty sweat on exposed skin of humans.  Species in this very large bee family are typically small, often less than an inch in length, may be eusocial (with a queen and worker castes), and are one of the most important pollinators of commercial crops, like squash, legumes, sunflowers, watermelons, apples, cranberries, blueberries, strawberries, tomatoes and peppers, as well as native flora appearing in all seasons in in woodlands and fields.

I followed one of the metallic Green Sweat Bees (an Agopostemon species) around the patch of New England Aster as it inserted its incredibly long tongue deep into the aster flowers.  Males have a yellow and black striped abdomen (mimicking a wasp?), while the female is a glossy green all over.

They are a challenge to photograph because their head is usually buried in the flower, and they pause only very briefly on a flower, dipping deeply into it, before moving on.

It looks like this sweat bee has a leg coming out of its mouth, but that is its long, flexible tongue being pulled out of one floret.  When it is not feeding, the tongue folds down on its ventral surface. Notice that this male’s body and legs are relatively pollen free, unlike the female in the next shots.

I don’t know if this female Green Sweat Bee is the same species as the male in the previous photo, but this shows how different the two sexes are in coloration.  And unlike the case of sexual dimorphism in bird or mammal species, the female Green Sweat Bee is hardly drab or well camouflaged.

Her hind legs and head are covered with pollen, unlike the male in the photo above.  She buried her head deeply into each flower as she foraged, transferring pollen as she went.

It’s possible someone that lives near me has some honeybee hives, because their numbers are way up this year. But there are still far fewer of them present on these early fall blooms than the Eastern Bumblebees and the small Sweat and Carpenter bees that swarm over these flowers.

Guardians of the desert

South of Tucson, Arizona, Saguaro cactus dominate the landscape with their giant trunks and arms reaching up, like those wacky, inflatable tube men you see along the highways, advertising a big sale of some sort.

Giant stems of Saguaro rise way above the rest of the vegetation, like giant sentinels.

Life stages of the Saguaro shown here–from an early (25 yr old) barrel shaped youngster, to 75 year old cactus just growing its first arm, to a mature many-armed giant 200 or more years old, to the woody remains of a dead Saguaro.

Saguaro are not only a dominant plant form in the Sonoran desert, but an integral part of the life cycle of this community.  It’s flowers provide nectar and pollen to insects, birds, and mammals, and its fruits are sought after by humans as well as many other desert animals.

Flowers appear on the tops of the cacti in April, remain open for less than 24 hours, but provide huge amounts of nectar and pollen to attract pollinators.

The Saguaro flowers are loaded with pollen from the hundreds of stamen projecting out the floral tube. Bats and birds reach the nectaries at the base of the flower with their long tongues.

After Gila Woodpeckers have drilled out nest cavities in the dense wood of the Saguaro, a variety of other bird species may use the nest holes as protection from the sun’s heat and for their own nests.

A pair of Gila Woodpeckers nesting in Saguaro. Cactus Wrens and  Elf Owls might get a chance to use this nest hole once the Woodpeckers are finished with it.

And of course, they make wonderful subjects for aspiring photographers…

Stocking up for the winter

We wait all summer for New England Aster to show off its beautiful lilac-purple to bright pinkish flowers, and it never disappoints.

Dense clusters of flowers attract a variety of pollinators in the fall with bright-colored flowers, lots of pollen, and nectar.

Besides being a very attractive addition to the garden, New England Aster is an important late-season resource for pollinators, especially Monarch butterflies as they fatten up before fall migration.  Flower nectar and pollen are energetically harvested by lots of bee species, as they top off their hive or overwinter nest supplies.

Honeybees, which I rarely see in my backyard, were numerous on this patch of New England Aster and were collecting both nectar and pollen.  This bee already has good-sized pollen baskets on its rear legs.

Common eastern bumblebees (center) were probably the most common bee on these flowers, but shared the resources with at least five other species of bees and a couple of species of Syrphid flies (hoverflies), seen in top left.

Both a large bodied (about as big as a honeybee) and a smaller bodied hoverfly worked the flowers. These are bee mimics, presumably avoiding predation by pretending to be fearsome stingers.  However, they have no weapon defense except their coloration, and have only one pair of wings (unlike bees and wasps which have two pair) with which they hover over and between flowers.

A smaller green sweat bee is unperturbed by the far larger bumblebee foraging next to it. There isn’t really much competition when there are so many flowers in this patch of aster.

I assume bees can smell or taste the presence of nectar in a particular flower, so some of the flowers got worked over very intensively by some bees that probed their tongues into every recess in the collection of disk florets in the orange center of the flower.

Honeybees and bumblebees are particularly good dispersers of flower pollen, as it easily attaches to the spines on their legs or hairs on their heads and bodies, as seen in the photo above.  The smooth exoskeletons of the body and legs of the hoverflies and sweat bees make them far less effective in transferring pollen from one plant to another.

If you live east of the Rocky Mountains where New England Aster grows, you might have noticed the profusion of aster flowers that has suddenly occurred over the past couple of weeks.  I assume synchronous blooming like this over widespread areas is probably triggered by the changing daylength, and is advantageous in pulling in large number of pollinators to maximize pollination and seedset in these asters.