Sticky Pollen

Arrowwood (Viburnum dentatum) in bloom. © Beatriz Moisset

 Some kinds of pollen are stickier than others. I marvel at that of arrowwood, Viburnum dentatum. These flowers attract numerous insects. The pollen coating can be impressive. It is hard to identify some of the bees when their features are hidden by abundant white dust.

Can you tell which kind of bee? © Beatriz Moisset

Probably the same bee. Hard to tell. © Beatriz Moisset

A closeup of another bee. © Beatriz Moisset

And one more. Take a look at those anthers. © Beatriz Moisset

Flower longhorn beetle taking a break. © Beatriz Moisset

Even the lady beetle larva gets coated with pollen. © Beatriz Moisset

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Beginners Guide to Pollinators and Other Flower Visitors

© Beatriz Moisset. 2014

Sneezeweed or Helenium

Halictid male bee on Helenium. © Beatriz Moisset

It is September, the days are getting shorter, the weather cooler. Plants put up a display that rivals or even surpasses that of spring. Asters, goldenrods, coneflowers and a number of other similar flowers create a golden explosion in gardens and meadows. Pollinators seem busier than ever, taking advantage of this bounty. Insect flower visitors love yellow and flowers seem to know it. They dress up in colors that attract their favorite visitors in the hope that they carry pollen to other flowers of the same kind. Pollinators, in turn, know that abundant resources await them in the bright yellow flowers.

Fig. 1. Three Helenium blossoms of different ages. © Beatriz Moisset

Let us look at one of these flowers in closer detail. Helenium, also called sneezeweed, has the same structure as sunflowers and asters, a crown of petals and a center made of little knobby structures called florets. Each one of those knobs is an entire flower which produces pollen and seeds. Each one needs to be pollinated in order to produce a seed. The dead heads you see later in the fall are little packages of these nutritious mature seeds that bring joy to passing hungry birds.

Fig. 2. Several Helenium or sneezeweed flowers. © Beatriz Moisset

The florets do not mature all at once. They proceed in an organized fashion from the outer ring to the center, row by row; they open and expose the pollen-carrying anthers and the pistils ready to receive pollen. They also fill up with nectar. Only one row or two at a time are ready to welcome visitors and to be pollinated. Bees know that. Even syrphid flies know that. You can see them moving from floret to floret until they complete the circle. Then they fly to the next blossom. They know enough not to waste time on the unopened flowers or the ones past their prime.

Bumble bee collecting pollen and nectar from open florets. © Beatriz Moisset

 Take a look at figure 1. The sneezeweed blossom near the center is quite fresh; most florets are still closed; only one is almost ready for pollination. The one in the upper right is halfway through; there are still some rows of unopened florets to go. The one below it is approaching old age, almost all done. Now, you can look at Helenium flowers and determine their approximate age just by looking at them. What do you think about the flowers in figure 2?

Another bumble bee. © Beatriz Moisset

 Smart pollinators, not only know where the food is in each flower, but also know that they will continue to find supplies in the following days. Bumble bees are known to faithfully come back to their favorite flower patches.

Sunflowers and asters do the same. See the following examples:

Agapostemon female on sunflower. © Beatriz Moisset

Halictid bee on coneflower. © Beatriz Moisset

Syrphid fly, Toxomerus on daisy. © Beatriz Moisset

 

Skipper on sunflower. © Beatriz Moisset

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Beginners Guide to Pollinators and Other Flower Visitors

© Beatriz Moisset. 2014

Buzz Pollination of Fabaceae Flowers

Flower of Senna. Observe the pores at the tip of the anthers

© Beatriz Moisset

It is interesting how several families of plants have evolved anthers that require buzz pollination, also called sonication, independently of each other. The organ that contains the pollen or anther of most flowers splits open when the pollen is ripe, making it available to the flower visitor. Buzz pollinated flowers do it differently. The anther remains closed, except for a pore at its tip. The only way to extract the pollen is by shaking the anther with just the right kind of vibration. Bumble bees are pros at doing this. Honey bees never developed the technique.

Close-up of the anthers © Beatriz Moisset

We are most familiar with the members of the tomato and potato family, Solanaceae. So much so, that some gardeners resort to a tuning fork or just an electric toothbrush to ensure pollination of the tomato flowers. Seeing pollen fly from the anthers during this process is a sight worth seeing. Another family with members that require buzz pollination is the Ericaceae; Blueberries, cranberries, azaleas and rhododendrons use this process.

Senna plant. © Beatriz Moisset

Perhaps, it is less known that some members of the pea family, Fabaceae, in the Caesalpinioideae subfamily also resort to this process. The genera Senna and Cassia, belong to this group. Recently I observed a bumble bee visiting the bright yellow flowers of a Cassia and was able to record the buzzing. The sound is unmistakable, quite different from the buzzing of flying. Watch the video of bumble bee on Senna and pay attention to the sound. You can compare it to that of a bumble bee pollinating an azalea.

Bumble bee, probably the common bumble bee. © Beatriz Moisset

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Beginners Guide to Pollinators and Other Flower Visitor

© Beatriz Moisset. 2013

Floral Emissaries

The raising sun turns the meadow into multicolored blankets of sparkling dewdrops. One flower stretches its petals lazily; it is still too early. She sets the table with a scented tablecloth, arranges bowls brimming with nectar; the anthers full of pollen have burst open exposing their golden dusty treasure and she wonders: Will the visitors come? Sadly, the weather turns bitter and windy and the sun finally refuses altogether to come from behind the clouds; wrong weather for winged visitors.

The next morning the wind is gone; the sun begins to warm the land and melt the dew drops so our flower feels her hopes rise. She is not alone; many others show their charms letting their aroma float in the breeze with the same hope of attracting guests. Better this way, so the callers can carry love messages between them.

The sun keeps climbing and finally a buzzing sound announces the arrival of one of the anxiously awaited visitors. A shiny metallic green bee stops briefly at a nearby blossom and then comes to her. Wisely, she has painted darker lines that point the way to the hidden nectar; thus the guest has no trouble finding it and drinks it avidly and briefly. The cunning flower has prepared just enough nectar to attract a visitor, but not so much that the bee would become satiated and return home without further visits. The guest brushes accidentally against the anthers and some pollen sticks to its hairy body. This is no accident; the flower has placed things just right where she wants them; now her pollen will travel to other flowers.

A parade of winged travelers follows on the next few days. Not all of them are shiny bees, there are others: fuzzy bumblebees, flower flies, a few flashy butterflies and moths and even a beetle.

Finally the pollen is all gone and the anthers begin to wilt. But the flower isn’t done yet because deep inside the ovary, at the very heart of the blossom, sit the future seeds. Now the ovary begins to bulge and its tip at the end of a little tube, the stigma, glistens with a sticky substance meant to receive the pollen from other flowers, the love messages brought unwittingly by the visitors. So the flower keeps inviting guests with its nectar and hoping that they come loaded with other pollens and ready to leave some of their cargo behind. Pretty soon the grains that were left on the stigma will begin to make their way toward the carefully sheltered future seeds. Only now is the flower satisfied of a mission accomplished and only now she allows the colors to fade and the scent to disappear; the petals shrivel and will soon fall to the ground.

Only the ovary remains with its seeds and with all the promises of generations to come. Later on it will become a juicy berry that will attract another kind of visitors, hungry birds and other small animals; they will carry the seeds, adventurous explorers, to farther meadows, to a new life away from the mother plant. But, that is another story.



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© Beatriz Moisset. 2012

For the Love of Flowers

Andrena, the bee, was sleeping her long slumber, comfortably inside her underground refuge, when something began to arouse her. She had been born the previous spring inside this cozy underground cell and she had grown well nourished by the mixture of flower’s nectar and pollen that her provident mother had stored. Later on, like the sleeping beauty, she had fallen into a deep trance for many months. But now it was spring and the soil was beginning to warm up. Did the warmth wake her up? Or was it some mysterious internal calendar? Suddenly that cozy cell that had been her nursery, her castle, her realm, her whole universe through the hot months of summer and cold ones of winter had become an intolerable prison. She had to get out.


Moved by this urge she began digging her way out. Her legs, never used before, were powerful enough to start loosening the earth that blocked her way to the outside world. With an unerring sense she moved toward the surface, perhaps following some ancestral memory of that world.

The task was arduous but she was young and strong and determined to find her way. It took her several hours and when her head finally emerged at the surface all her senses were bombarded by an accumulation of new sensations: light, colors, smells . . . She tried her wings for the first time and suddenly she found herself airborne. She marveled at her capacity for flying, zigzagging, rising and falling, making sudden turns. The surrounding world, immense and full of sunshine and strange sights, and her just discovered faculties were intoxicating. She kept coming and going taking notice of this unfamiliar land of her birth and its landmarks. She didn’t seem to get tired; there was so much to see. A hungry bird tried to catch her and missed, not because of her skill, but by sheer luck. She would learn to be cautious later on.

That morning she learned that she belonged to a small village of bees that, like her, were emerging from their prolonged sleep and getting drunk on light and air and new experiences. Their wings reflected the rays of the sun. Sometimes, if you walk on a meadow at the right time, you can see them against the sky like constantly moving dots of light.

A dogwood blossom makes a convenient waiting room for a group of boy bees spending the night together in wait for the girls

There were some males among them; some had emerged the previous day and now, past their first exhilaration they were moved by another urge that kept getting stronger by the minute. The scent of the females acted like a magnet and several, full of eagerness, approached and surrounded our little bee. She resisted their advances, not for lack of desire, which she was beginning to discover, but because she wanted only the best suitor. That would be her legacy to her children: the best father that she could find. One male prevailed over the others and joined with her. Now, in delirious ecstasy, both of them, linked by love, rose in the air and flew to a nearby branch where they could enjoy their time together in seclusion.

After their romance and carrying inside herself the sperm of the male, Andrena became all mother. Only one motivation would dictate her actions from now on: to ensure the best for her future children. She was passing on her mother’s heritage even though she would never know neither her mother nor her children.

She started the search for a nest site. What better place than the one her mother had chosen the previous year? It was a patch of soil, warm and with plenty of sunshine, safe from floods and not chocked by vegetation. She landed and started walking in circles looking for the best spot, but somebody else, perhaps her own sister, had already started setting housekeeping there. An angry buzz let her known that she was not welcome nearby. No problem, there were several similar spots not far from this one and she had no trouble finding a good one.

Andrena began digging the hard soil, just like her mother had done a year ago. It was harder than digging up from her cell; the soil was compacted and she had to use all the energy of her young jaws and legs. She kept working full of determination until she realized that she was getting hungry and thirsty.

She flew away from her nest searching for food. A delicious aroma told her that she had found what she was looking for. There were many flowers in the meadow, she landed on an open blossom, found its nectar guided by the scent and drank it thirstily. Andrena went from flower to flower until satiated, then returned to her task.

Back to work she went digging deeper and deeper. Evening came and she needed to rest. What better place than the tunnel she had dug? It was safe there and protected from the night chill. Andrena slept comfortably. The next morning, when her muscles were warm enough, Andrena resumed her work until something told her that she had arrived at the right place; then she started digging a side cavity, this one was a chamber like the one that had sheltered her through her infancy and long sleep.

A mother Andrena gathering food for her babies; her feathery legs make good baskets for the pollen

Now she needed to prepare the chamber for her offspring. That meant many trips to the meadow full of flowers. There she loaded rich pollen in the baskets on her legs and nectar, which she carried in her crop. It took her many trips to have enough for her purpose and another day passed by. She kneaded the pollen and nectar into a thick paste and made it into a tidy ball that nearly filled the whole cell. Satisfied, Andrena laid an egg on top of this loaf and sealed the chamber with some soil

Once again she kept digging another branch of the tunnel, making a new chamber, gathering food, laying a new egg and so on. The days flew by. Sometimes she couldn’t go to work because the weather was foul so she hunkered down, feeling safe in the darkness of her tunnel. One day our little bee escaped a sudden death without knowing it. When she approached a blossom she noticed something different but didn’t give it much importance. Fortunately for her, another bee beat her to this flower. Somewhat annoyed Andrena flew to another one without noticing that a crab spider had caught the other bee in her clutches and paralyzed her with her poison.

All that coming and going wore out her thin wings. They began to fray at the edges and so the day came when, after gathering her usual load of supplies in the meadow, she tried to take off but the extra weight and her aging body and worn out wings prevented her from doing so. She tried again and again but the wind kept slamming her against the ground. So finally, with a sigh and without regrets she surrendered to her fate, knowing that her mission was complete, the new generation was well provided and would repeat the story next spring.

Thus ended one little life made of flowers and sunshine, of dark tunnels and security.

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© Beatriz Moisset. 2010

The pure magnificent green bee

A female Augochlora pura gathering pollen on her leg baskets

Among the many metallic green bees that you see in the summer there is a particularly beautiful one, Augochlora pura. It doesn't have a common name but its scientific one means "pure magnificent green" and it is a very fitting one.

You may have seen this little jewel diligently visiting flowers to gather food for her family. You would be surprised to find out where she takes her load of pollen and nectar. If you could follow her, which isn't easy, you would see her arrive at an old fallen log and disappear inside a crack of the loose bark. That is where she has started building a home for her babies, in the space between the bark and the log. She builds chambers using her own saliva, some wax from her abdominal glands and loose debris, abundant in such places. Later on, she kneads the cargo that she brings from flowers into tiny loaves that look like golden tiles with which she paves the inside walls of the chamber. When there is enough food to feed one baby all the way to adulthood she deposits just one egg and seals the cell; afterward she starts building another one and so on.

A dead log, home to a few metallic green bees

An unhappy mother whose nest has been disturbed when I lifted a chunk of bark. You can see the ripped open cell, where the larva lays surrounded by a nice supply of "bee loaves" made of pollen and nectar

The babies grow on such rich food and emerge in the fall. By then the mother is approaching the end, her wings are torn and frazzled. The bees of the new generation, on the other hand, have a youthful look, with glossy wings and nicely coated by delicate hairs; these are the ones you are likely to see in October and November.

Young females getting ready to hibernate in late fall, November

The young bees mate promptly. This is the end of it for the males who die shortly afterward. But the recently mated females visit some of the abundant fall flowers stocking up on food to see them through the long winter and get busy finding cracks under wood to spend the cold month in safety. By the end of November you are not likely to see any more activity from these handsome bees; but rest assured that they will emerge from their seclusion next spring when the sun warms up the land and when blooms are ready and waiting for them.


 
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© Beatriz Moisset. 2010

Bees in the Garden

A bee house for mason bees. These bees are solitary, meaning that each one tends to her own brood, about six to eight babies, and all each one needs is a hole the size of a pencil in a block of wood. They do not live in large hives with thousands of workers like honey bees. You can get fancy and create a handsome bee house like the one my son in law did for me.


Watching the comings and goings of your little tenants can be almost as much fun as watching birds at your bird house, and there is no reason to fear their stings. Unlike honey bees they are very gentle; I have let them climb on my hand without problems. They emerge in early spring and are busy through April and May and, perhaps early June. You won't see more activity until next year. You can see the video.


This one emerged from its long winter sleep shortly before Easter, so I call it my Easter bunny bee.



Let us provide a habitat for some of the numerous helpers to our gardens, pollinators, a few tips provided by:
Urban Bee Gardens
Selecting Plants for Pollinators

You may also want to build nest boxes for those bees that make their homes in cavities.
There are instructions in several websites:
National Wildlife Federation
Audubon. Bring on the Bees.

Or you may choose to buy a bee house from one of the several companies that make them, such as:
Northwest Nature Shop
Mason Bee Homes
Knox Cellars
(I am not endorsing any one, just saving you some leg work or mouse work).

Beginners Guide to Pollinators and Other Flower Visitors

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A Busy Pollinator and a Relaxed One

An industrious little bee gathering food for her babies and pollinating flowers along the way. It methodically collects pollen without missing any and then promptly flies to the next flower.



The bee is very industrious and visits many flowers in a very short time. The flower fly, on the other hand, takes its precious time gobbling up pollen, so it visits fewer flowers overall.

The Life of a Flower

© Beatriz Moisset

Let us take a simple flower, the simplest you can think of, the one you drew when in Kindergarten. A yellow circle surrounded by petals. It looks like a daisy or a sunflower or an aster or a number of flowers with petals arranged like sun rays and a circle or disk at the center. Well, there is a surprise here; such a flower is far from simple. It has a very complex structure, in fact it isn't just a flower but a whole bunch of tiny flowers. Look at the little parts that comprise that yellow center. What a surprise! Each one looks like a tiny flower all by itself: five petals and a center with little things inside that resemble the center of many other flowers that you have observed at various times. Well, that is exactly what they are. Each one is a flower, called a floret; they are all clustered together.

Each floret contains all flower parts: petals, anthers, stigma

© Beatriz Moisset

You may wonder about the petals that surround this cluster of flowers. Here is the answer: there are two kinds of flowers in this interesting bouquet; only the ones that make the outside rim have petals, the large petals that we see. They are called ray flowers while the ones in the center are called disk flowers. It would be nice if all technical jargon were as obvious as this.
In a newly opened sunflower or helenium, the disk flowers are just like little knobs. The next day the outer line of disk flowers has opened and you can see the sex parts, the pollen and seed producing parts, sticking out. Afterward, each day or so a new row of flowers open. The old ones begin to wilt; they look open and a little dry. Eventually one smaller circle after another opens and passes its prime.
Now let us observe the pollinators that come and visit the flower. They go directly to the freshly opened florets. They have nothing to do with the unopened ones, nor with the wilted ones. They find pollen and nectar only there and they know it. All this goes according to the plans of the flower; this works just right to ensure pollination.

© Beatriz Moisset

One interesting thing is to look at the older flowers that have completed their cycle. The ray petals stay fresh and bright for a few days longer although that flower is no good to pollinators any more and it doesn't need visitors either; right now it is busy growing the seeds that will mature later on.
You may wonder why it continues to look attractive to pollinators. The reason is that a large clump of flowers is more likely to attract pollinators that are passing by than a smaller clump, with many dry blossoms in between. It is like you going shopping; a mall where many stores are closed or vacant is likely to drive you away rather than attract you. Once there, you aim for the store that interests you. Pollinators do the same; they notice the larger displays of flowers than the smaller ones, with the certainty that they will find some food there.

Helenium. The flower on the left is young, only a few florets opened

The one at right is older, most florets are past their prime

© Beatriz Moisset

Such flowers are skilled engineers, and good marketers. They know their clients and how to satisfy their demands, and they get good returns. Other flowers are arranged differently; they use different attractants; their timing varies; but they all know how to maintain a successful partnership with their pollinators.
The clients, on the other hand, know how to use this resource. You can see a bee visiting methodically all the florets and probing them with its long articulated tongue in this video

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© Beatriz Moisset. 2010

Metallic green bee, a good pollinator

The pure golden green bee, Augochlora pura, is a singular bee, smaller than a honey bee and looking like a shiny metallic little robot bee. There are several other metallic green bees related to this, they compete in beauty and they are all good pollinators of many wild flowers.

In the spring she builds her nest under the bark of rotten logs. If you thought that dead trees or large dead branches had no use you were wrong. To this very nice pollinator they are prized real estate, just the right place to raise her family safely and well protected. She searches for the right dead tree diligently and, if your garden is one of those perfectly manicure ones, you will not have the pleasure of her and her family's company.

She builds a small chamber in the space between the loose bark and the solid wood using her own saliva and secretions. She packs it with a storage of pollen and nectar very carefully kneaded and shaped as tiny loaves. She encrusts the inner walls of the chamber with these loaves arranged like tiles. When she has enough to feed one baby from birth to maturity she lays a small egg and shuts the chamber. She surrounds it with loose debris which abounds in such places and starts the construction of other chambers. You may find a couple of rows of four or five of these cells. The mother bee dies at the end of the summer and the new generation spends the rest of the year comfortable and safe until the next spring.