Autumn Photos and Phenology

Seasonal changes happen quickly in Minnesota during October and it’s interesting to watch the progression into autumn. For example, swamp milkweed seed pods break open, male goldfinch feathers transform from bright yellow to olive green, chipmunks and other rodents stash nuts and seeds for the winter, and bees and most other insects have either died or are hibernating until spring.

Naturalists use the term phenology to refer to these changes.  Phenology is the study of the changes that occur in plants and animals from year to year — such as flowering, ripening of fruit and nuts, emergence or disappearance of insects, and migration of birds — especially the timing and relationship of these events with weather and climate.  It also can include other observations, such as the occurrence of the first frost, the date on which a body of water freezes, and when specific constellations are visible in the sky.  Here are a few examples of current autumn phenology that I photographed along the Snake River in Pine County, MN:

 Northern red oak leaves begin to change color.

Northern red oak (Quercus rubra) leaves begin to change color.

Wild rose hips ripen to cherry red.

Wild rose hips (Rosa acicularis) ripen to cherry red.

Swamp milkweed (Esclepias incarnata) seeds pods release their silky seeds.

Swamp milkweed (Esclepias incarnata) pods release their silky seeds.

An eastern chipmunk collects acorns, hickory and hazelnuts in its pouches to store in its den for the winter.

An eastern chipmunk stuffs bur oak acorns into its pouches to store in its den.

Puffball mushrooms are common in autumn.

Puffball mushrooms appear in autumn.

Everyone who observes nature and records their observations contributes to the science of phenology.  If you’re interested in contributing your own observations, there are several organizations online, including:  “Nature’s Notebook” at the USA Phenology Network, the University of Minnesota’s Minnesota Phenology Network  and the National Science Foundation’s “Project Budburst”.

First Hard Frost of Autumn

Early yesterday morning, as Orion sailed high overhead and strings of bright stars washed the sky in spite of an almost-full moon, the first killing frost zapped gardens in the urban core of St. Paul-Minneapolis.  About two weeks later than the average date of October 7th, the first hard frost turned basil and impatiens to mush, bedraggled morning glories and hyacinth beans, and shriveled the last blossoms of Japanese anemones and toad lilies.  But one hardy bloom survived: a newly opened cluster of climbing ‘Henry Kelsey’ roses.  The rose faces south and grows next to our brick garage, which helps to shelter it from north winds.  The National Weather Service predicts nighttime lows in the upper 20s the next two nights, so the roses won’t last much longer.  However, their fresh, simple beauty was a gift on a gloomy, unseasonably chilly day.  To read more about Minnesota weather, seasons and related topics, visit Updraft Blog: Weather and its Underlying Science at

Rosa 'Henry Kelsey' (Canadian Explorer Series) survived the season's first hard frost.

Yellow leaves of an ash tree accent Rosa ‘Henry Kelsey’ (Canadian Explorer Series) blooms that survived the season’s first hard frost.

Autumn Leaves

When leaves change color in autumn, people often say that the trees are “putting on their fall colors”.  In fact, many of the yellow and orange colors are already present in the leaves during the summer and are masked by chlorophyll, a green pigment. (The red and purple colors are primarily made in late summer as sugars are trapped in the leaves.)  Scientists haven’t yet identified all of the factors that influence the color change in leaves, but the primary factor is the decreasing amount of daylight in the fall.  As the days shorten, the veins that bring water and nutrients to leaves for chlorophyll production slowly close off.  Without nutrients, the chlorophyll dies and the leaves’ other colors are unmasked.

Lemony ash leaves (Fraxinus pennsylvanica) fall and mingle with Canada cherry leaves (Prunus virginiana).

Lemon-colored ash leaves (Fraxinus pennsylvanica) fall among Canadian red cherry tree branches (Prunus virginiana).

Green ash leaves have changed to bright lemony-yellow and are pulled from the tree by wind and rain.  They are the first trees in our St. Paul neighborhood to change color, along with white ash.  Black walnut, hackberry and a few sugar maples also have begun to change, with just a hint of muted color showing in red maples.  (More about autumn leaves in future posts.)

 Green ash (Fraxinus pennsylvanica) is one of the first trees to change color and drop its leaves.

Green ash (Fraxinus pennsylvanica) is one of the first trees to change color and drop its leaves.

To learn more about why leaves change color in the fall, visit the USDA Forest Service, or the Morton Arboretum websites.

Autumn Garden Creatures

Last Friday was a golden day with gentle sun, temps in the 70s and a southerly wind.  I walked at lunchtime and spent a few minutes in our back garden observing insects, birds and chipmunks.  It was the final day before a strong Canadian cold front and soaking rains moved in — and probably my last chance until spring to enjoy some of the garden’s inhabitants:

Autumn meadowhawk dragonflies, which fly late into autumn, still patrolled the garden.  The reddish-colored mature females, with clear wings tinted amber at the base and red spots at the top, added jewel-like color to the changing garden.

A male autumn meadowhawk dragonfly (Sympetrum vicinum) suns on a stone wall in the garden.

A female autumn meadowhawk dragonfly (Sympetrum vicinum) suns on a stone wall in the garden.

A celery looper moth visited the garden from morning until dusk each day for more than a week.  Though it’s not colorful, the contrast between the chocolate-brown wings and the bright silvery-white curved markings makes it glow in the sunlight.  Though looper larvae can be agricultural pests, the adults pollinate many varieties of plants.  This one seemed to prefer Sedum ‘autumn joy’.

A celery looper (   ) nectars on Sedum 'autumn joy'.

A celery looper (Anagrapha falcifera) nectars on Sedum ‘autumn joy’.

Celery looper

Side view of a celery looper moth.

Syrphid flies, also known as hover flies or flower flies, are small insects that zip between flowers much quicker than bees and wasps.  Syrphid flies are bee and wasp look-a-likes, but they don’t sting or bite!  Many species are helpful in the garden for two reasons:  The adults pollinate flowers and the larvae eat aphids and leaf hoppers, which cause a lot of damage and disease in plants.  They are called hover flies because they often hover in midair over the garden before zooming off in a new direction — sometimes flying backwards.  They are known as flower flies for their pollinating presence in the autumn garden.

A Syrphid fly, (Eristalis) pollinates native goldenrod.

A syrphid fly, (Eristalis) pollinates native goldenrod.

Another species of Syrphid fly pollinates garden asters.

Another species of syrphid fly (Helophilus) pollinates garden asters.

Hidden among the garden plants, an eastern chipmunk gathered seeds to store for winter use in its nearby den.  There’s a stable chipmunk population in our urban neighborhood, in spite of many gardeners’ attempts to eradicate the rodents.  At least the chipmunks retire to their dens until spring, unlike squirrels, which raid the garden during the growing season and the suet feeder during the winter months!

An eastern chipmunk surveys the backyard from its perch on our back steps.

An eastern chipmunk (Tamias striatus) surveys the yard from its perch on our back steps.

The backyard bird population is changing as many bird species migrate south.  For example, most of the warblers, orioles and swallows have left; ruby-crowned kinglets, yellow-rumped warblers and white-throated sparrows are passing through from further north.  Daily visitors to our garden, trees and hedges include northern cardinals, blue jays, American goldfinches, black-capped chickadees, white-breasted nuthatches, American robins and a brown creeper. I don’t have a telephoto lens yet, so I don’t photograph many birds.  An excellent website with photos, key facts, bird calls and other information is

Lastly, bumble bees and honey bees nectared on the Sedum ‘autumn joy’ and garlic chives. (Earlier in the summer, I pruned the sedum to different degrees so that it would continue to bloom late into autumn.)  The sedum and asters were the main attraction for insects last week.  I haven’t seen either bee species since the weather turned cold and rainy.  I miss their industrious presence and look forward to their return next spring.

A honey bee nectars on garlic chive blossoms (Allium tuberosum).

A honey bee nectars on garlic chive blossoms (Allium tuberosum).

A bumble bee (Bombus) nectars on Sedum 'autumn joy'.

A bumble bee (Bombus impatiens) nectars on Sedum ‘autumn joy’.

October Garden

Last weekend’s heavy rain and thunderstorms were badly needed to help gardens, trees and shrubs prepare for winter.  The downside is that the rain knocked off most of the blossoms on garden phlox, helenium, Russian sage, hosta and other flowering plants.  A few species continue to bloom in small numbers providing nectar for native bees and honey bees.  Here’s a sample of what’s still blooming in our garden in St. Paul, Minnesota, on October 11:

Japanese toad lily (Tricyrtis)

Japanese toad lily (Tricyrtis ‘Tojen’).

Aster novii-belgi with green bee (

(Aster novii-belgi) with green metallic bee.

Dwarf wood asters (Aster novi-belgii 'Woods pink')

Dwarf wood asters (Aster novi-belgii ‘Woods pink’).

Thin-leaved coneflower (Rudbeckia triloba) is a native wildflower that appeared under our ash tree a few summers ago.  The tree is a favorite perch for birds and gray squirrels and

Thin-leaved coneflower (Rudbeckia triloba) is a native wildflower that appeared under our ash tree a few summers ago. The tree is a favorite perch for birds and gray squirrels, which must have either dropped or excreted the seeds.

The yellow bloom of Chrysanthemum rubellum 'Mary Stoker' will develop pink highlights as it ages.

The yellow blooms of (Chrysanthemum rubellum) ‘Mary Stoker’ will develop pink highlights as they age.

Purple morning glories last all day in the gentler autumn sunlight.

Purple morning glories last all day in the gentler autumn sunlight.

A few hyacinth beans (Dolichos lablab) continue to blossom.

A few hyacinth beans (Dolichos lablab) continue to blossom.

Russian sage (Perovskia atriplicafolia) with Rosa 'Henry Kelsey' (Canadian Explorer series) in the background.

Russian sage (Perovskia atriplicafolia) with Rosa ‘Henry Kelsey’ (Canadian Explorer series) in the background.

Native goldenrod

Native goldenrod brightens up our autumn garden.

Early October Wildflowers: Zigzag Goldenrod

Twelve or more species of goldenrod grow in Minnesota.  All provide an important source of autumn nectar to bees, butterflies and insects, and also give a burst of long-lasting color at the end of the growing season.  Most goldenrod species grow in sunny locations, but zigzag goldenrod (Solidago flexicaulis) prefers shady woods and woodland borders.  It’s smaller, daintier and better-behaved than many of its cousins.

Zigzag goldenrod with aerial yellowjacket (Dolichovespula arenia).

Zigzag goldenrod with aerial yellowjacket (Dolichovespula arenia).

A patch of zigzag goldenrod grows in dappled sun near a hazelnut thicket along the banks of the Snake River in east central Minnesota

A patch of zigzag goldenrod (Solidago flexicaulis) grows in dappled sun near a hazelnut thicket along the banks of the Snake River in east central Minnesota.

Known also as broad-leaved goldenrod, it has oval-shaped leaves rather than thin narrow ones typical of many goldenrods.  The stem bends a little bit at each node, hence the name zigzag.  An interesting fact:  Sometimes allergy sufferers blame their misery on goldenrod, but ragweed is the true culprit.  Unlike ragweed pollen, which is wind-dispersed, goldenrod has sticky pollen that is dependent upon insect pollination.  So, if you’re sneezing in the fall, it is primarily caused by the pollen of ragweed and nettle!  To learn more about the difference between ragweed and goldenrod, visit the University of Minnesota Extension website for an excellent, succinct overview.

Early October Wildflowers: Spotted Jewelweed

In early October, wildflowers in shades of orange-gold, yellow, purple and white light up Minnesota’s roadsides, fields, woods and riverbanks.  One of my favorites is spotted jewelweed (Impatiens capensis), or touch-me-not.  Its small flowers are bright orange with red spots and are shaped like tiny funnels or cornucopias.  The name jewelweed refers to the way that water droplets bead up like shiny jewels on the plant’s leaves, and also to the blossom’s jewel-like appearance.  Touch-me-not refers to the ripe seed pods, which burst open and expel the seeds if touched.  When our teenage son was little, we loved popping open the ripe pods and watching the seeds fly out.

Spotted jewelweed (Impatiens capensis)blossom and ripening seed pods.

Spotted jewelweed (Impatiens capensis) blossom and ripening seed pods.

Native to much of Canada and the United States, spotted jewelweed grows along streams, rivers, damp roadsides and other moist, shady spots.  The one I photographed was growing in a shady wet area about four feet from the edge of the cabin road.  Hummingbirds, which are attracted to the bright, red-spotted blooms, are the main pollinator of spotted jewelweed.  The nectar is contained within spurs that are easily reached by the hummer’s long beak.  A closely related plant is pale touch-me-not (Impatiens pallida) which is light yellow with just a few reddish-brown spots.

Related Video:  Spotted jewelweed pods popping open.

Lake Darner Dragonfly

I love dragonflies for their aerial acrobatics, beautiful colors and ancient presence — they’ve flown Earth’s skies for about 300 million years.  In Minnesota, a few species of large, colorful dragonflies are active into October.  Last week I found a darner (Aeshna) dragonfly sunning itself on a nearby cabin.

A lake darner dragonfly (Aeshna eremita) rests in the sun.

A lake darner dragonfly (Aeshna eremita) rests in the sun.

Called darners for the resemblance of their long abdomen to a darning needle, the blue or mosaic darners can be confusing to tell apart.  I believe the one I photographed is a lake darner (Aeshna eremita), based on the notched side stripe, the vivid greenish-blue jewel-like coloration of the stripes, its length (about three inches) and its vertical perching position.  It flew away before I could get close enough to see its facial markings.  Lake darners are native to Canada and the northern United States, and are the largest species of North American darner.  They prey on mosquitoes, wasps, mayflies and most other kinds of soft-bodied insects.

Related Websites:

The Dragonfly Website includes a great overview of dragonfly facts in its “Frequently Asked Questions” section. features a profile and photos of the lake darner, along with thousands of other plant and animal species.