Thrifty flowers

Pollen is a valuable commodity. The less pollen needed, the more energy is left for other functions. Flowers resort to several strategies to economize on pollen. Some use a method called explosive pollination, others resort to buzz pollination. Both methods are well illustrated by official state flowers.

Mountain laurel in bloom. © Beatriz Moisset

Explosive Pollination of Mountain Laurels

Mountain laurel (Kalmia latifolia), Pennsylvania’s and Connecticut's state flower, has a singular way to ensure that its insect visitors carry pollen to other flowers of its species. The unopened blossoms present little knobs which give them a funny look. Their function becomes apparent when the flower opens. They are pockets that hold the anthers trapped. Anthers are the part of the flower that produces male cells, pollen.

Mountain laurel flower before an insect's visit.  © Beatriz Moisset

Flower tripped by an insect. © Beatriz Moisset

In most flowers the anthers are free and exposed to spread their pollen at the slightest touch of a flower visitor. The mountain laurel has a different strategy. The pollen is well protected against rain and wind; but, when a pollinator lands on the flower searching for nectar, the weight acts as a trigger, causing the taut stem of the anther to spring. The anther hits the pollinator gently on the back and gives it a dusting of pollen.

This method allows mountain laurel flowers to produce only a moderate amount of pollen because most of it ends up where it is intended, on the body of a pollinator, rather than being wasted in other ways.

Connecticut: Mountain laurel

Pennsylvania: Mountain laurel

Explosive Pollination of Pea-like Flowers

Texas Bluebonnet. Wikicommons © Jacopo Werther

Other flowers encase both the pollen-producing parts and the female parts, or stigma, into a sheath. Some members of the pea family, Fabaceae, have flowers that resemble a butterfly, this is why this subfamily is called Papilionoideae, papilio meaning butterfly. The top petal is large and shaped as the sail of a ship and is called the banner. Two side petals are called wings, and the bottom two petals are merged into one forming a sheath that encloses both the anthers and the stigma. This structure looks like the keel of a boat and it is so called.

Structure of a papilionoid flower. Wikicommons. © David Richfield

When a pollinator lands on a blossom, its weight triggers a mechanism causing the keel to spread open and the anthers and stigma jump up out of the enclosure. This is called tripping. The insect has to be heavy enough to cause such reaction. Some bumble bees are pros at this task; honey bees, on the other hand, dislike being pounced upon. After a few times, they learn to sneak around and steal the nectar through a small opening at the base of the keel. Only novices perform pollination. Once they learn this trick no more pollen is transferred to the stigmas. Nevertheless managed honey bees are widely used to pollinate alfalfa and clover. Bee hives provide a large labor force that makes up for this deficiency. Some bumble bees, especially the short-tongued species, are also inclined to a little larceny. However, they are generally considered highly competent pollinators of alfalfa and clover.

Clover, another papilionoid flower. © Beatriz Moisset

Texas’ bluebonnet (Lupinus) and Vermont’s red clover (Trifolium pratense) need to be tripped. Six species of lupines, all of them called bluebonnets because of their appearance, live in Texas. All six of them are considered the state flower. The red clover, Vermont’s state flower, on the other hand, is not a native plant. It is an important crop used to feed livestock.

Texas: Bluebonnet

Vermont: Red Clover

Buzz Pollination or the Salt Shaker Technique

Other flowers make the pollinators work for pollen in a different way. Interestingly enough, honey bees never learned how to do the job I will describe, but native bumble bees and numerous species of bees are real pros.

Azalea Andrena bee pollinating azalea. Observe the pores at the tips of the anthers. © Beatriz Moisset

In most flowers the pollen is made available to pollinators as soon as it is ripe. The anther splits open. We all have seen the golden dust many flowers have. If we touch it, it sticks to our fingers. Rhododendrons and azaleas do something else. They keep the pollen enclosed inside the anther. It can only come out through a small opening at the tip. Several other native flowers, like tomato and blueberry have a similar characteristic.

In order to extract it, the bee has to cling to the anther and give it a good shake. It accomplishes this by vibrating its flight muscles while keeping the wings still; it is like running the car engine in neutral. Pollen comes in clouds and clings to the body of the pollinator. Later, the bee proceeds to package its loot in the little baskets of the hind legs.

Buzz pollination of azalea. Video. © Beatriz Moisset

Two states have official flowers that exemplify this method of pollination, Washington has chosen the Coast Rhododendron (Rhododendron macrophyllum) and West Virginia has another species of Rhododendron (Rhododendron maximum). Georgia’s official wildflower, azalea (Rhododendron prunifolium), follows the same system of pollination; its official flower is the rose; but, fortunately, they decided to honor a native plant in addition to a non-native flower.

Georgia (official wildflower): Azalea

Washington: Coast Rhododendron

West Virginia: Rhododendron

Other plants select their pollinator clientele through other methods. Some hide the nectar rather than the pollen. A different set of skills are needed to deal with these flowers as we'll see in the next post.

References

Pollination of mountain laurel

Image illustrating the parts of a Papilionoid flower

Red clover pollination (also alfalfa)

Legume pollination

Bluebonnet pollination

List of articles
Beginners Guide to Pollinators and Other Flower Visitors

© Beatriz Moisset. 2015

Gardening for Honorary Butterflies (Mint Moths)

Not all moths fly at night and not all are drab. Some deserve the name of honorary butterflies. In fact sometimes they are mistaken for them. Sorry I tricked you by using the word butterflies in the title (not really); but I was afraid that most would ignore this article if they just saw the word moths. The fact is that there are ten times more species of moths than of butterflies; that they are very important components of ecosystems and worth welcoming in our gardens. Some are very beautiful and can give visual enjoyment to the gardener. To me, most if not all are beautiful each in its own way. But I know people who dislike, fear or hate moths in general. I hope that at least they take time to look and learn to love the pretty ones.

I will save some of the most striking ones, such as hummingbird, imperial and Luna moths for later. I will start with some that many people are unaware of and amazed when they first see them.

The crambid snout moths represent a family (Crambidae) with more than 850 species in North America. They get their common name from the appendage that sticks out on front of their heads. Some of them, the members of the genus Pyrausta feed on plants of the mint family, so I will be calling them mint moths, although they don't really have a common name. Most of them are brightly colored and are seen during the day.

Pyrausta orphisalis (Orange Mint Moth) on mountain mint
©Beatriz Moisset

The larvae of the orange mint moth (Pyrausta orphisalis) feed on a variety of mints and sometimes you cans see signs of their feeding, especially at the buds and newer leaves. But the damage is not known to reach serious proportions. It is good to remember that caterpillars are bird food. So it is a good idea to have a few well behaved caterpillars such as these ones to attract birds to the garden. It is also a pleasure to spot this very attractive moth resting on a plant of mint.

Pyrausta signatalis (Raspberry Pyrausta) on mint
©Beatriz Moisset

The raspberry mint pyrausta (Pyrausta signatalis) is also richly colored and earns its name because of the raspberry color of its wings. The larvae feed primarily on spotted beebalm (a member of the mint family), they also feed on a few related plants such as wild bergamot and scarlet beebalm.

Pyrausta tyralis
  © Bob in swamp Flickr

 Another member of this genus, even more striking in its coloration is the Coffee-loving pyrausta (Pyrausta tyralis). This one breaks the mold with its feeding habits, a peculiar feat. It gets its name because it likes wild coffee (Psychotria nervosa) found in Florida. It also feeds on some Asteraceae such as dahlia and bidens.

It is worth mentioning that there are many species of mint moths in Europe. Here is a gorgeous one: the golden mint moth (Pyrausta aurata).

Pyrausta aurata © Bramblejungle Flickr

In summary, if you want to attract these honorary butterflies to your garden plant a variety of mints including beebalm which by the way is also good at attracting hummingbird moths and hummingbirds.

Moth as Pollinators
List of articles
Beginners Guide to Pollinators and Other Flower Visitors

© Beatriz Moisset. 2012 

Pine Barrens, Plants and their Pollinators

Pine tree shedding pollen

The Pine Barrens of New Jersey is well worth a visit. The Pinelands Preservation Alliance is dedicated to preserve this unique treasure. Let us take a look at some of the pollinators of its plant community.

The predominant tree and the one that gives the name to the place is the pine tree, especially the pitch pine (Pinus rigida). It uses the wind for pollen transport. This ancient method of pollination existed long before there were any flowering plants or any pollen carriers. The features that make wind pollination possible are: the production of vast amounts of pollen and the relative proximity of plants to each other.

Some members of the flowering plants group have reverted to the time honored tradition of wind pollination; they do just fine without the help of pollinators. Such are oaks, birches, most maples, grasses and sedges, among others. Notice that such plants grow fairly close to each other and produce abundant pollen.

Plants that employ the services of pollinators invest some of their energy in producing flowers that attract and recompense the visitors. This investment is compensated by the reduced need to produce large amounts of pollen. Flowers have an array of different techniques to accomplish this. Here are some found in the Pine Barrens.

Sweetbay Magnolia (Magnolia virginiana). Magnolias are among the oldest flowering plants. Their ancestors resorted to the only available pollinators at that time, rather clumsy ones, such as beetles. Beetles mouth parts are good for biting and chewing, not for delicately gathering pollen and nectar. They chew on the flowers along with feeding on some pollen and can make a big mess. Magnolias continue to be pollinated mostly by beetles and they tend to have rather tough, leathery petals to protect themselves against such insults.

Wild cherry (Prunus serotina). The shape of its flowers is relatively simple and open, its pollen and nectar are easy to reach, thus a large number of species of bees and even other insects visit these flowers. Some of these flies mimic bees very skillfully and manage to fool not only hungry birds but even some human observers.

Mountain laurel in bloom

Mountain laurel (Kalmia latifolia). This attractive flower has a very peculiar shape. The anthers (the part of the flower that carries the pollen) remain caught inside little pockets made by the petals; their stalks or filaments remain taut and ready to snap. When an insect lands on the flower they spring to action. Each anther comes out of the pocket and gives the insect a good dusting of pollen.

Blueberries, cranberries (Vaccinium corymbosum, Vaccinium macrocarpon and others). The anthers of these flowers are shaped very differently from those of most other flowers. They don’t split open exposing the pollen; instead they have an opening at the end of the anther. The way to get the pollen out requires some skillful work by the pollinator. It has to hang on to the flower and give it a good shake; the way you shake a salt shaker. Some bumblebees and many other native bees are very adept at this task. The blueberry bee (Habropoda laboriosa), can pollinate so many flowers in her short adult life of a few weeks that her labor can result on $20 worth of blueberries, probably more at today’s prices.

Honey bees, on the other hand, never learned how to perform this task. They do visit blueberries and cranberries and accomplish pollination although not as efficiently as the native bees and bumblebees. However, large blueberry and cranberry operations resort to honey bees because of the convenience of placing hives on the fields and because such large tracts of land fail to provide nesting places for native bees. Pollinating these berries is stressful for honey bees; they are not well adapted to such diet and suffer as a consequence. Wild grown berries, on the other hand, get all their needed pollination from native bees.

Lady slipper (Cypripedium acaule). The lovely orchid known as lady slipper can play unpleasant tricks on pollinators; its elaborate shape is nothing but a seductive trap with a complicated escape route. The flower yields an aroma that some bees find irresistible. When they reach the flower, they perch at the edge of the sac and frequently slip and fall. Soon they find that they can’t get out the way they came in because the inside walls are very slippery and the lip of the sac curves inwards making it even harder. Fortunately the orchid has provided a ladder at the back of the flower and a very narrow passage that leads back to freedom. The bee that struggles through this tunnel gets a sac of pollen, called pollinia, stuck to its back. It will remember the unfortunate experience long enough to move away from that patch of orchids; but shortly afterward, it will be quite willing to repeat the experience because its little brain will have forgotten all about it.

Magnolias and Beetle Pollination
Lady slipper

Beginners Guide to Pollinators and Other Flower Visitors

List of articles

© Beatriz Moisset. 2012

Mountain laurels instead of rose bushes?

Last year I was traveling along the Blue Ridge in May and was pleasantly surprised by the beauty of the blooming mountain laurels. I had to look again and again to convince myself that what I was looking at wasn’t a rose garden but just a natural grove of mountain laurels.

I want that look in my garden. I have two rose bushes which I inherited from the previous owner of the property and I want to replace them. The advantages are obvious to me. Roses are not native; they provide no food for pollinators. Mountain laurel, on the other hand, is pollinated primarily by native bumble bees.

It has a peculiar system of pollination. The unopened blossoms present little knobs which give them a funny look. When the flowers open, the function of these little knobs become apparent. They are pockets that hold the anthers (the pollen carrying part of the flower) trapped. It still doesn’t explain why this is so; in most flowers the anthers are free and exposed, better to spread their pollen at the slightest touch of a flower visitor.

The mountain laurel has a different strategy. The pollen is well protected against rain and wind; but when a pollinator lands on the flower searching for nectar, the weight acts as a trigger, causing the taut stem of the anther to spring. The anther hits the pollinator gently on the back and gives it a dusting of pollen.

Mountain laurel flowers produce a moderate amount of pollen; but most of it ends up where it is intended, on the body of a pollinator, rather than being wasted in other ways. It seems like a highly economic method to spread the pollen.

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