Posts tagged ‘phenology’

Northern Minnesota phenology report: November 2009

By John Latimer, KAXE Radio, Grand Rapids

Ruby meadowhawk by Jim FrazierThe last of the meadowhawk dragonflies will put in an appearance in early November. These small, bright red, insects are among the last to fly about in the fall. A warm day or two in the early part of the month will send them out in a last and probably fruitless search for other flying insects.

Flickr photo “Ruby Meadowhawk” by Jim Frazier. Original.

If you have been observing them throughout the fall you may have noticed them flying in tandem with the female periodically touching her abdomen to the grass. She is depositing eggs. Her strategy is to place her eggs on stalks of grass that will be inundated in the spring. Once awash the eggs will begin to develop and the larval stages will terrorize the shallow ponds and lake edges until late summer when they will emerge and terrorize the flying insects.

Dragonfly by Chris CoomberThose eggs mistakenly laid in the grass that may be your lawn will likely never develop. No one is perfect and least of all the meadowhawk dragonflies, but what they lack in foresight about those areas likely to flood they make up for in sheer numbers of eggs laid. Some of them will end up underwater and the species will survive.

Flickr photo “Dragonfly” by Chris Coomber. Original.

In the case of the meadowhawk dragonflies they survive the winter as eggs or larvae, but what about the Compton’s tortoiseshell or Mourning cloak butterflies? How do they survive the cold? They over-winter as adults and without an approach to overcome the cold they would freeze and die. For many insects the strategy is freeze avoidance.

There are three elements to freeze avoidance. First, the insect produces an anti-freeze which circulates in the blood. These special proteins bind with any ice crystals that may form keeping them small and preventing them from doing damage.

Chionea species by C WoodSecond, they produce sugars and sugar based alcohols which act to lower the freezing point of any water in the body. These typically take the form of glycerols that by mid-winter may constitute 20 to 25% of the insect’s total body weight.

Flickr photo “Chionea species” by C Wood. Original.

The final part of a freeze avoidance strategy involves finding a dry location. Staying away from water and the resulting ice is imperative. Ice can act as a nucleator for the development of further ice crystals. The butterflies must find secure dry locations, other insects might construct waterproof cocoons or some other personal protection, but the butterflies lack this ability. This perhaps explains why I find so many of them in my garage.

John Latimer is well known throughout northern Minnesota for his phenology work. He appears weekly on KAXE radio in Grand Rapids, and audio and twitter archives are available here. His work is a frequent feature on MyMinnesotaWoods.  This article also appeared in the Duluth Senior Reporter.  It is printed with the author’s permission.

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November 9, 2009 at 11:15 am Leave a comment

Northern Minnesota phenology report: October 2009

By John Latimer, KAXE Radio, Grand Rapids

Fall color from Oberg Mtn. Allison Eklund photo.

Fall color from Oberg Mtn. Allison Eklund photo.

The arrival of fall is best announced by the leaves of the trees turning color. For many years it was assumed that these colors were in the leaves from the beginning and that as the tree prepared for winter it stopped producing chlorophyll and the intrinsic colors were revealed. Recent studies have shown that the colors are not in the leaves and must be produced by the tree.

From an evolutionary perspective simply turning color would be a waste of energy because the pigments produced are lost when the leaves fall. There must be a reason why the trees would invest in the color change. Two theories have emerged as possible explanations.

One theory is that the color is a signal to insects to stay away. Many insects approach trees in the fall to lay their eggs and in the spring these eggs will hatch and begin an attack on the tree. There is some evidence that insects avoid the most colorful trees. The trees with the brightest colors will self select because they will experience the least insult from pests. Ultimately these trees should come to dominate the forest. That they don’t is the source of much conjecture.

The problem is that some trees do not turn color in the fall. Rather they just drop their leaves while still green. Scientists that support this protectionist theory contend that there is always going to be some natural variation within the plant community. Research indicates that those trees under the greatest pressure were the ones that evolved to have the brightest colors.

Jack pine needles about to drop in fall. Esagor photo.

Jack pine needles about to drop in fall. Esagor photo.

Other scientists have noted, especially here in the far north, that by the time trees begin to turn color the majority of their insect pests have perished.  Where then is the pressure to turn color for defense? They contend that the trees turn color to mitigate the effects of sunlight on the leaf as it shuts down.

The entire photosynthetic process must be shut down in the fall. The tree needs to carefully dismantle the chemicals used in the process, nitrogen, and phosphorus among others will be maintained in the tree to be used again in the spring. All this housekeeping requires energy that comes from photosynthesis, yet this is the process that is shutting down.

Leaves cannot use all the energy striking their surfaces in the fall and the excess can cause damage. Anthocyanins, those molecules that cause leaves to turn red, act as a sunscreen allowing the leaf to get its work done without destroying the chemicals the tree is trying to extract.

Scientists produced trees in the laboratory that were unable to produce the colors associated with fall. While these trees prospered in the greenhouse they were unable to ship nutrients to the tree for storage in the fall. This supports the sunscreen theory, but the sunscreen is only present in those trees that produce anthocyanins. The trees that turn yellow manufacture a chemical called carotenoid and this has no effect on sunlight. Currently they are arguing that there is another, as yet undiscovered, chemical doing the screening.

So it goes, the two sides concede that the other may be partly correct. Possibly the leaves turning color may accomplish more than one task. I am just glad that they do turn color in the fall. Whatever the reason it is a time of stunning beauty.

John Latimer is well known throughout northern Minnesota for his phenology work. He appears weekly on KAXE radio in Grand Rapids, and audio and twitter archives are available here. His work is a frequent feature on MyMinnesotaWoods.  This article also appeared in the Duluth Senior Reporter.  It is printed with the author’s permission.

October 5, 2009 at 9:01 am 3 comments

Northern Minnesota phenology report: September 2009

By John Latimer, KAXE radio, Grand Rapids

Garter snake: Flickr photo by jereandregan. Click for original.

Garter snake: Flickr photo by jereandregan. Click for original.

In late September and early October garter snakes begin to search out places to hibernate. It isn’t a matter of choice. Their food supply is going to disappear and cool temperatures will force all cold-blooded critters to slow down. To avoid freezing to death the snake must locate a place below the frost line.

Abandoned anthills, up-turned stumps, rock crevices, and even foundations of buildings are among the suitable choices. It is challenging for snakes to find appropriate places to hibernate. In some areas they will congregate in large numbers to spend the winter together. In Manitoba the garter snakes all gather at a rock outcrop known as the Narcisse snake dens. Estimates range as high as 8000 garter snakes using this location. There simply is nowhere else to go. Here in northern Minnesota there are a few more options but it is still possible to have dozens of snakes heading to the same spot to spend the winter.

Garter snakes at the Narcisse snake dens, Manitoba. Flickr photo by James Sapara. Click for original.

Garter snakes at the Narcisse snake dens, Manitoba. Flickr photo by James Sapara. Click for original.

Unlike bears or groundhogs, snakes do not sleep away the winter nor do they live off stored fat. They simply slow down. Their metabolism is reduced to the point where they may not even lose any weight during the winter. They usually avoid eating in the last few weeks before entering their hibernacula. Food taken late in the fall might remain undigested in the stomach and rot. They may be sluggish but they are alert and if necessary and possible, they will retreat further down to avoid frost.

Garter snakes are remarkably cold tolerant. They are among the last to seek out shelter from the cold. Often they can be seen basking on roads in the fall. This cold tolerance extends their range across the United States, with the exception of the arid southwest, and into sub-arctic Canada. They are the most northerly distributed serpents in North America.

Fall color Flickr photo by Bill.Roehl. Click for original.

Fall color Flickr photo by Bill.Roehl. Click for original.

As September trails off into October the deciduous forest puts on a show unrivaled in all of nature. Beginning with the black ash and continuing through to the various members of the willow family all will add their splash of color to the surrounding woods. Some are predictable and will be the same color year in and year out while others react to the conditions and surprise us with a new color each year. The sumacs shine red with a brilliance demanding your attention. The speckled alder seldom change at all and suddenly drop their still green leaves. Quaking aspen become a dependable yellow, while their cousins the big tooth aspens may follow along with yellow or they may show us a shade of orange not seen outside of the deer hunting season.

The real wonders come from the maples. Here we find the true measure of the fall. There are three factors that influence the leaf color, pigments that are present in the leaves, length of the nights, and weather.  The most significant of the three is the number of hours of darkness. Rainfall, food supply, and temperature are too unpredictable for the tree to rely on as triggers for shutting down. Only the increasing length of the night hours is unvarying enough to begin the process that results in fall colors.

Red maple Flickr photo by H Robertson Photography. Click for original.

Red maple Flickr photo by H Robertson Photography. Click for original.

These colors are the result of three pigments, chlorophyll, carotenoids, and anthocyanins. Chlorophyll is responsible for the green color seen all summer. It is the foundation for photosynthesis that produces the sugars the tree stores to make new leaves in the spring. Carotenoids supply the yellows, oranges, and browns in plants like bananas, corn, and carrots.

The anthocyanins provide the reds and blues for apples, bunchberries, raspberries, and blueberries. The first two chemicals can be found in the leaf throughout the summer, but the anthocyanins are produced in the fall as a result of bright sunlight and excess sugars. As night length increases chlorophyll production ceases and the underlying colors begin to show through.

If the weather is warm and sunny with cool but not freezing nights the leaves continue to produce sugars. Because the leaf is already in shutdown mode the avenues to move the sugar to the roots are constricting. The combination of lots of sugars in the leaf and bright sunlight combine to produce lots of anthocyanins. In these circumstances we will see sparkling reds, deep purples, and crimsons. In the absence of these favorable factors the carotenoids that are always present in the leaves will show through and the colors will tend to be more yellow orange and brown.

Wet warm falls tend to favor the yellow colors. A perfect year for brilliant colors would have a warm wet spring, followed by favorable summer weather and warm and sunny fall days with cool , but not freezing, nights.

In the end what causes the leaves to fall? All the while we are enjoying the fabulous fall colors a layer of corky cells is forming at the point where the leaf joins the stem. This is called the abscission layer. Basically the tree is forming a scab to prevent the loss of fluids at the junction of the leaf and the stem. Once the scab is complete the leaf is ready to fall. In some trees the leaf drops as soon as the layer of cells is complete, in others like the oaks and ironwoods the leaves may hang on all winter. In the case of the young ironwoods it seems as if the emergence of the new leaves in spring provides the impetus to drive the old leaves off. It is often April before these leaves fall.

John Latimer is well known throughout northern Minnesota for his phenology work. He appears weekly on KAXE radio in Grand Rapids, and audio and twitter archives are available here. His work is a frequent feature on MyMinnesotaWoods.  This article also appeared in the Duluth Senior Reporter.  It is printed with the author’s permission.

September 7, 2009 at 8:05 pm Leave a comment

Northern Minnesota phenology report: July 2009

By John Latimer, KAXE radio, Grand Rapids

Swamp milkweed. Flickr photo by Anita Gould. Click for original.

Swamp milkweed. Flickr photo by Anita Gould. Click for original.

July 1, 1991 The first pin cherries are turning red. I wouldn’t call them ripe because it will take a bit of time before the sugars in the fruit really begin to develop. I ate my first ripe raspberry today so as I wait for the pin cherries to ripen I won’t starve. The water hemlock has begun to bloom. Another flower seen blooming today is the swamp milkweed. The beautiful red flowers are a delight to the eye.

July 14, 2002 The Atlantis fritillary winter survival must have been great because I can’t remember seeing this many before. They can be told from the great spangled fritillary by the presence of a black border along the trailing edge of both wings. The absence of the black border on the trailing edge of the wings and the broad stripe of yellow on the underside of the wing set the great spangled fritillary apart from its close cousin the Atlantis fritillary. The day of the butterflies ends with an observation of the Harris checkerspot.  All three of these butterflies are mostly orange, though the smaller checkerspot has more black than the others.

Atlantis fritillary. Flickr photo by Jerry Oldenettel. Click for original.

Atlantis fritillary. Flickr photo by Jerry Oldenettel. Click for original.

July 25, 2007 There are two Eastern pondhawk females sitting on a rock wall near Prairie Lake. They are startlingly green with black on the last few segments of the abdomen and the very tip is touched in white. The smooth aster, Canada goldenrod and the pearly everlasting are all beginning to bloom today. The Canada goldenrod is a favorite among the goldenrod gall flies. The select this variety almost exclusively to lay their eggs upon. Their feet taste the plant when they land, and they can tell whether or not this is the proper species.

A warm sunny day can be a perfect time to observe butterfly behavior. The males of many species are quite territorial. The sulfur butterflies are a good species to watch defend their area. A male will spend a good deal of energy and time flying after other males that attempt to infringe upon his space. These skirmishes usually involve a spiraling flight that begins low near the ground and can climb to fifty feet or more.

Eastern pondhawk. Flickr photo by Vicki DeLoach. Click for original

Eastern pondhawk. Flickr photo by Vicki DeLoach. Click for original.

Puddling is another behavior that can be seen without great effort. Sometimes just driving around after a rain storm will afford a chance to watch as males gather and share a drink at the edge of a puddle. Or if you have ever seen butterflies congregate on feces and wondered just what was going on, both of these activities are related. Typically these are male butterflies and they are attracted to these spots in search of trace minerals.

One of the current hypotheses about this behavior is that the males, by concentrating these trace minerals; make themselves more desirable to the females. The females need these minerals as well and can get them from the male during copulation. This transfer, think of it as a dowry, allows the female to spend more time and energy developing the eggs that will be the next generation of the species.

One hot July day I spent an afternoon moving a pile of bricks that had been salvaged from some demolished building. I was re-acquainted with a world I had left behind as a child. There was an entire ecosystem living in there. Ants, salamanders, spiders, millipedes, beetles of unknown names, were all living in the crevices surrounding the bricks. It was a menagerie of the miniscule.

Some of these insects are remarkably well defended. Ants carry chemicals which alert one another to the presence of danger. The millipedes secrete hydrogen cyanide through pores located near the legs. This poison is strong enough to deter almost all of the predators they are likely to encounter. Among the beetles are the bombardiers whose scalding hot spray can be selectively shot in any direction. And the spiders, those wolves of the insect world, stand ready to attack anything that crawls or flies into their range. They use chemicals to subdue and liquefy their chosen prey. For all of the innocence of its appearance it is a dangerous world down there among the rocks, bricks, and leaves.

If you are one of those people who like to tramp the woods all year around then in July keep a look out for the blue bead lily or yellow clintonia. This lily is quite common across the eastern half of the United States and can be found as far south as Alabama. The bright blue berries are a most tempting sight but close observation will reveal few if any attempts at eating them. That is because they contain calcium oxalate crystals. Sharp microscopic needles, these crystals imbed themselves in the flesh of the mouth and throat and cause pain and swelling. Look for a cluster of two to five or six berries at the top of a single stalk above a pair of lily-like leaves. And then avoid the temptation to taste them.

Pin cherry fruit. Flickr photo by George Bott. Click for original.

Pin cherry fruit. Flickr photo by George Bott. Click for original.

As July comes to a close there will be several tasty fruits ripe and ready to tempt you. The blueberries will be ready, though much depends on the weather leading up to the end of July. A frost at the wrong time or the wrong amount of moisture can wipe out a crop. Pin cherries ripen in July. Some find these a bit tart, but if you can wait and the birds don’t eat them all, they become quite sweet. And if you are a wine maker you should be watching the chokecherries. They are a bit too astringent for my palate, but they make a wonderful wine.

John Latimer is well known throughout northern Minnesota for his phenology work. He appears weekly on KAXE radio in Grand Rapids, and audio and twitter archives are available here. We hope his work will be a frequent feature on MyMinnesotaWoods.  This article also appeared in the Duluth Senior Reporter.  It is printed with the author’s permission.

July 2, 2009 at 6:14 am 1 comment

Northern Minnesota phenology report: June 2009

By John Latimer, KAXE radio, Grand Rapids

White-faced meadowhawk. Photo by Anita363

White-faced meadowhawk. Photo by Anita363

6/4/2007        I watch as a small unidentified dragonfly shelters behind some trees and shrubs, suddenly, an insect is swept from the cover and the dragonfly as quick as a shortstop on a line drive shifts and grabs.  This was a day for dragonflies. I was on the shores of Deer Lake in central Itasca County and spent part of the day wandering through a black spruce swamp. The dragonflies were omnipresent. I saw the white-faced meadowhawk, the four spotted skimmer, several black saddlebags and the unidentified specimen referred to above. Dragonflies are becoming as popular as the birds when it comes to observing them. They are easy to find, colorful, and field guides are becoming readily available.

6/16/2001       There are two great crested flycatchers in the garden with a phoebe and an oriole. This is the first time I have seen so many flycatchers in one place. Toss in the oriole and you have a pretty good day in the garden, unless you are a flying insect. The great crested flycatchers are more common than you might suspect. Listen for their loud “Wheeep! ” call. Once you learn that sound you’ll find it easy to spot one. They are not shy, and like many of the flycatchers they often sit on an exposed perch and sally out to hawk insects. The great crested flycatchers are gorgeous,  pale yellow on the belly, gray below the beak, with an olive green back and cinnamon red tail. It is well worth the trouble to learn their call and search them out.

Spreading dogbane. Flickr photo by edgeplot

Spreading dogbane. Flickr photo by edgeplot

6/24/1997       Spreading dogbane has begun to flower. The beautiful white bell shaped blossoms are streaked with pink. These are a favorite plant for many of the summer butterflies. On one spectacular day I found ten species of butterflies and one moth. Off the high ground down in the swamp the pitcher plants are blooming. They augment their energy requirements by capturing insects. Many of the plants in the nutrient poor swamps have made one or more adaptations to survive.

A warm sunny day can be a perfect time to observe butterfly behavior. The males of many species are quite territorial. The sulfur butterflies are a good species to watch defend their area. A male will spend a good deal of energy and time flying after other males that attempt to infringe upon his space. These skirmishes usually involve a spiraling flight that begins low near the ground and can climb to fifty feet or more.

Puddling is another behavior that can be seen without great effort. Sometimes just driving around after a rain storm will afford a chance to watch as males gather and share a drink at the edge of a puddle. Or if you have ever seen butterflies congregate on feces and wondered just what was going on, both of these activities are related. Typically these are male butterflies and they are attracted to these spots in search of trace minerals.

One of the current hypotheses about this behavior is that the males, by concentrating these trace minerals; make themselves more desirable to the females. The females need these minerals as well and can get them from the male during copulation. This transfer, think of it as a dowry, allows the female to spend more time and energy developing the eggs that will be the next generation of the species.

One hot July day I spent an afternoon moving a pile of bricks that had been salvaged from some demolished building. I was re-acquainted with a world I had left behind as a child. There was an entire ecosystem living in there. Ants, salamanders, spiders, millipedes, beetles of unknown names, were all living in the crevices surrounding the bricks. It was a menagerie of the miniscule.

Some of these insects are remarkably well defended. Ants carry chemicals which alert one another to the presence of danger. The millipedes secrete hydrogen cyanide through pores located near the legs. This poison is strong enough to deter almost all of the predators they are likely to encounter. Among the beetles are the bombardiers whose scalding hot spray can be selectively shot in any direction. And the spiders, those wolves of the insect world, stand ready to attack anything that crawls or flies into their range. They use chemicals to subdue and liquefy their chosen prey. For all of the innocence of its appearance it is a dangerous world down there among the rocks, bricks, and leaves.

Bluebead lily. Flickr photo by manual crank.

Bluebead lily. Flickr photo by manual crank.

If you are one of those people who like to tramp the woods all year around then in July keep a look out for the blue bead lily or yellow clintonia. This lily is quite common across the eastern half of the United States and can be found as far south as Alabama. The bright blue berries are a most tempting sight but close observation will reveal few if any attempts at eating them. That is because they contain calcium oxalate crystals. Sharp microscopic needles, these crystals imbed themselves in the flesh of the mouth and throat and cause pain and swelling. Look for a cluster of two to five or six berries at the top of a single stalk above a pair of lily-like leaves. And then avoid the temptation to taste them.

As July comes to a close there will be several tasty fruits ripe and ready to tempt you. The blueberries will be ready, though much depends on the weather leading up to the end of July. A frost at the wrong time or the wrong amount of moisture can wipe out a crop. Pin cherries ripen in July. Some find these a bit tart, but if you can wait and the birds don’t eat them all, they become quite sweet. And if you are a wine maker you should be watching the chokecherries. They are a bit too astringent for my palate, but they make a wonderful wine.

John Latimer is well known throughout northern Minnesota for his phenology work. He appears weekly on KAXE radio in Grand Rapids, and audio and twitter archives are available here. We hope his work will be a frequent feature on MyMinnesotaWoods.  This article also appeared in the Duluth Senior Reporter.  It is printed with the author’s permission.

June 8, 2009 at 9:08 pm Leave a comment

Can’t see the flowers for the trees?

By Philip Potyondy, University of Minnesota Extension

The giants and their tiny flowers

black locust blooming on Midtown Greenway in Minneapolis, MN

Black locust May 31st, 2009 Midtown Greenway in Minneapolis, MN

The scent of spring wafts into our nostrils and affirms spring is here.  Is that quinte-scent-ial smell rising from below our knees or is it falling from the heavens?  Maybe a little of both.  High above our heads in the tops of trees flourish a multitude of flowers.  This sounds a bit … well… flowery … but it is true.  In the tops of our colossal statuesque canopy forming titans are sprightly little flowers fit for a pixy.

“…And the flowers and the trees…”

The Birds and the Bees, Jewel Akens 1965

Red maple female flowers April 23, 2007 Brainerd, MN.  These showy red flowers are insect pollinated. (image by esagor)

Red maple female flowers April 23, 2007 Brainerd, MN. These showy red flowers are insect pollinated. (image by Eli Sagor)

One of the hallmarks of spring is when the crab apples and other fruit trees are in bloom.  In about the second week in May In the Longfellow neighborhood in south Minneapolis, many of the streets are lined with brightly colored and honey scented crab apple trees this time of year.  Without going too far down the botany lingo path of gymnosperm, angiosperm, carpel, and sporophylls with fused margins, consider that in order for trees to reproduce (make more trees) they’ve got to make a seed.  And before many trees, or any kind of plant, can make a seed it needs to make a flower.  And that flower needs to be pollinated.  The majority of flowers on trees are pollinated by the wind or by insects; a few are pollinated by hummingbirds.

The size, color and shape of a flower is linked to how it gets pollinated.  Wind pollinated trees depend on the wind to move a pollen grain from a male flower to a female flower. It is most effective for them to put energy into making a lot of flowers, pollen, and eventually a lot of seeds versus making a big colorful flower.  If a tree is trying to woo a specific insect to carry its pollen directly to another flower, it is a good use of plant energy to make a larger attractively colored flower.  It is also worth the plant’s energy to make enough pollen so that the friendly little bug gets a meal in exchange for courier services.  You can make a guess about how a flower is pollinated based on what the flower looks like.

American elm flower April 19, 2009 Minneapolis, MN.  The large bud in the upper left is less than an inch long and will eventually open as the leaves expand.  The flowers are wind pollinated.

American elm flower April 17, 2009 Minneapolis, MN. The large bud in the upper left is less than an inch long and will eventually open as the leaves expand. The flowers are wind pollinated.

Fresh cut flowers

By the time some of the more showy flowers bloom, like magnolias, crab apples and lilacs many of many less noticeable flowers have already bloomed in yards, in the woods and on boulevards.  Many of these flowers come out before the leaves.  One way to view and observe the more dainty specimens is to bring them into your home.

Prune off some approximately pencil thick branches off a tree in your yard.  Low hanging branches or water sprouts growing from a previous pruning cut are fine candidates for harvest since they will potentially be pruned soon.  You can display them, much like cut flowers from the florist, with water in a vase.  Place your piece of spring in a location you will see often, like where you eat breakfast.  American elm is a great tree to take a cutting from early in the spring.  Watch the buds early in the spring and collect a cutting just after you notice something starting to emerge from the buds.  The cutting on your table will develop and bloom at about the same rate as the flowers up in the tree’s canopy.  This is a great way to watch up-close how the flowers develop and change in a short amount of time.  Use a magnifying glass or hand lense to get an even better view.

American elm flowers April 19, 2009 Minneapolis, MN.  Freshly emerged winged fruit is called a samara.  Each samara holds one seed.  Seeds are wind dispersed using those wings to float in the slightest breeze.

American elm flowers April 19, 2009 Minneapolis, MN. Freshly emerged winged fruit is called a samara. Each samara holds one seed. Seeds are wind dispersed using those wings to float in the slightest breeze.

Pursuing petals

Viewing tree flowers, especially the smaller ones, is not as easy as noticing large brightly colored flowers.  It takes a bit more observation and focus but is rewarding.  It can be hard to see the details on branches of large trees.  Look for low hanging branches.  Yards and natural parks are good places to find branches that haven’t been pruned up too high for viewing.  One way to view details in the crown of a tree is to use binoculars.  You can view from the ground or even from an upper story window in your house.  Another use of the binoculars is to look through one of the lenses the wrong way to see the detail of a little flower up close.  You need to have the object you are viewing almost touching the glass on the small end and your eye on the big end.  The best way to notice when a tree is blooming or changing in some way is to look at trees that are part of your daily routine.  Glance at the tree or shrub nearest to your front door when you get home.  Check the tree at your bus stop when you arrive at work.  Trees are always changing and can be enjoyed through watching these subtleties.

Bur oak flowers and leaves May 13, 2009 St. Paul, MN.  These male flowers are known as catkins.  They are wind pollinated. (image by Eli Sagor)

Bur oak flowers and leaves May 13, 2009 St. Paul, MN. These male flowers are known as catkins. They are wind pollinated. (image by Eli Sagor)

Floral calendar

Seasonal changes in a plant, including blooming, is determined by a number of factors.  One way plants regulate when they bloom is by measuring the length of the night.  Plants are also impacted by temperature and other environment factors.  Botanists use growing degree days(GDD) to predict when a plant will bloom.  This system calculates blooming dates by measuring daily temperatures but variations in temperature from year to year make it difficult to put blooming times on a specific date on a calendar.  See the table below for approximate times to look for selected tree flowers.  If you are wondering about other species check out the resources below or simply keep a keen watch on your tree.

Enjoy discovering tree flowers.  This is a fine activity to do on your own, but better yet share your excitement with a friend, neighbor, or family member.

Share your favorite tree flowers and when you saw them blooming in the comment section below.

Further investigation

May 29, 2009 at 11:28 am 4 comments

Northern Minnesota phenology report: May 2009

By John Latimer, KAXE radio, Grand Rapids

There is no place I’d rather be than northern Minnesota in May and June. The rush and rebirth of life in the fields and forests is astonishing. Birds sing from every tree, shrub, and thicket. These same perches are bursting forth with life of their own. Leaves, flowers, and fruits develop with a speed that deceives. Though they seem slow and measured the flowers and fruits race to complete their mission, which is to spread seeds to insure survival. Now is the time to walk amid all this ruckus and observe its magic.

Photo: Flickr/~flutterby~. Click for original.

Photo: Flickr/~flutterby~

Purple clematis blossoms drape from the shrubbery. The lovely pale purple, bell-like flowers are quite large, perhaps two and a half to three inches long. The vine climbs and twists through the understory. The plant has no tendrils to support its stems, relying on the leaf petioles to wrap around supporting structures. These petioles turn woody and remain attached to the branches even after the vine has died away.

Clematis are not plentiful. The greatest populations occur here in northeast Minnesota, though even here they are never abundant They are somewhat shade tolerant but will not grow in the darkest thickets. They prefer moist, slightly acidic soils and I find them most often in the company of aspens. Often the vines will climb on young aspen, or hazelbrush, and I have seen them draped all over downy arrowwood. From the middle of May until the end of the first week of June look for the lovely bell shaped purple flowers of the clematis. You won’t be disappointed.

Flickr photo by guppiecat. Click for original.

Photo: Flickr/guppiecat.

While the clematis bloom the painted turtles will be wandering about search out the perfect spot to lay their eggs. Wandering is perhaps not the right word, since the gravid females often return to the same locations year after year. Open sandy sites are selected and an urn shaped chamber is dug with the hind legs. Once the chamber is completed she lays eight or nine eggs on average, though she may lay as many as twenty.

The eggs are leathery and white. They are slightly oblong averaging an inch and a quarter long by three quarters of an inch wide. The developing turtle inside takes about eighty days to mature. Many of the hatchlings will remain in the nest throughout the winter. This explains the presence of the tiny turtles found in the spring well before the females have had a chance to lay their eggs. One nest studied by scientists experienced temperatures as low as twelve degrees, yet the turtles emerged unharmed in the spring.

Sea (not painted) turtle eggs. Photo: Flickr/muhawi001

Sea (not painted) turtle eggs. Photo: Flickr/muhawi001

Another effect of temperature on developing turtle eggs is its ability to determine the sex of the embryo. If the nest is in a sunny location and the temperature climbs above eighty-four degrees most of the turtles will be female. Conversely temperatures below this mark will produce mostly males. Inventories of populations reveal a nearly one to one relationship between males and females, so the system seems to be in balance.

It is estimated that fewer than two percent of the eggs laid each year result in adult turtles. There are many critters out there searching for a meal of fresh eggs. Fox, skunks, and raccoons destroy many nests. Hatching is only the beginning of the gantlet that they must run. Crows, mink, garter snakes, fish and even larger turtles all will make a meal of these tender morsels. And if that weren’t bad enough there are all those roads to cross. Who hasn’t seen the carnage that results from inattentive drivers. For three hundred million years turtles have faced these depredations and survived. The Painted Turtle can live for forty years in the wild, so as we move into spring, and they gather on logs to bask, let’s try to give them a brake.

John Latimer is well known throughout northern Minnesota for his phenology work. He appears weekly on KAXE radio in Grand Rapids, and audio and twitter archives are available here. We hope his work will be a frequent feature on MyMinnesotaWoods.  This article also appeared in the Duluth Senior Reporter.  It is printed with the author’s permission.

May 8, 2009 at 10:48 am 1 comment

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