a beautiful riverside wildflower garden

What a surprise to find a lush wildflower garden growing in the damp soil at the edge of the St. Croix river at the Arcola Bluffs trail.  A trail along the river’s edge led me through dense clumps of Cardinal flower, Blue Lobelia, Obedient plant, and Prairie Ironweed.

cardinal flower-Lobelia cardinalis-

There were hundreds of individual Cardinal flower stems growing here in the semi shade and moist forest soil along the St. Croix river.

cardinal flower-Lobelia cardinalis-

With this many attractive red flowers, you would expect to see hummingbirds, and sure enough they showed up right as I began noticing the dense flower patch.

ruby-throated-hummingbird-on-cardinal-flower-1

Shot earlier in my backyard wildflower garden, but Ruby-throated Hummingbirds do love this plant.

white cardinal flower-Lobelia cardinalis

Among the hundreds of individual plants, there was one genetic mutant, a white form of the Cardinal flower.

White mutants of brightly colored animals or plants are usually genetic recessives, and are rare in the population. I imagine hummingbirds might skip over the nectar resources in this plant (wrong color to attract them), so it might not set much seed, which further contributes to its rarity.

Blue Lobelia - Lobelia siphilitica-

Another Lobelia species, the Blue Lobelia, was also growing in the riverside wildflower garden, although in much lower density.

Obedient plant - Physostegia virginiana-

I spotted just a few individuals of Obedient plant in this “garden”, although this plant is usually an aggresive colonist of open spaces in my backyard wildflower garden.

Prairie Ironweed - Veronia fasiculata-

Prairie Ironweed seems to like the wet river bottomland as well as it does the open prarie habitat. It’s large flowerheads were particularly attractive to honeybees.

Prairie Ironweed - Veronia fasiculata-

Has this lovely wildflower garden always been here? Did I just happen to hit it during its peak flowering? Other wildflower enthusiasts have reported lush blooms of cardinal flower along the backwaters of the Mississippi and St. Croix recently (late July-early August), so maybe I have just never discovered these little patches of colorful diversity along the rivers.

From the blind…

The hummingbirds have been quite active lately in the wildflower garden, so I set up the blind this morning to see if I could capture some of the action.

a blind for wildlife photography

I don’t normally keep so much of the window space open — just enough to poke my telephoto through the open space toward the garden.  The blind is about 10-20 feet from the plants the hummers prefer.

There seem to be four hummingbirds buzzing around the cardinal flowers and the nectar feeder — one very shy but aggressive male, and three female-looking birds that could be a female and her two juvenile offspring.

Ruby-throated Hummingbird on cardinal flower

Lots of bees in this photo as well as the hummer probing the red cardinal flower

Ruby-throated Hummingbird

Every now and then, one would perch on the tomato cages in the vegetable garden, about 10 feet away.

My goal was to get some photos of the very shy (or wary) male Ruby-throated Hummingbird who dashes in to drink from the nectar feeder, but rarely goes to the flowers.

Ruby-throated Hummingbird male

He seems bigger than the others and has a darker throat, so he is easy to spot, but very difficult to photograph.

Ruby-throated Hummingbird male

He even hides behind the nectar feeder, giving an obstructed view of his ruby throat.

Ruby-throated Hummingbird male

At last, one quick shot of him next to (instead of in back of) the Cardinal Flowers.  Those wings beat 53 times a second while they hover, so cranking up the shutter speed is required.

The hummingbirds are probably feeding voraciously now, stockpiling calories to store as fat for their long migratory journey south to wintering areas in Mexico and Central America.  Apparently a particular hummingbird follows the same route each year, but they don’t migrate in a flock, nor do young hummers necessarily follow their parents.  They just know the way south.

A perfect fit

Ruby-throated Hummingbirds love red flowers.  In my garden, they particularly like the Cardinal Flower, which sends up 4 foot tall stalks with a bright red plume of flowers that develop sequentially from bottom to top of the stalk over a 4-6 week period. Apparently, it produces some really good nectar too, because it is the first flower they visit in the morning.

Here I come -- bring out the nectar.

Here I come — bring out the nectar.  This little female Ruby-throated Hummingbird was extremely cooperative, foraging for several minutes on a clump of cardinal flowers, while I sat in a very hot blind about 15 feet away.

Sometimes the probing is just a test to see what might be there, as the bird tastes with the tip of its tongue.

In this shot, her bill is inserted only part way into the flower, and her head is completely clear of the flower structures.

In this shot, her bill is inserted only part way into the flower, and her head is completely clear of the flower structures.  This foraging position won’t accomplish what the plant intended the bird to do in return for a nectar reward.

When there is sufficient nectar at the base of the flower, hummingbirds hover for several seconds in place while they mop up every drop.  In this case, the bird’s head almost disappears into the flower as it inserts the bill all the way in.

It looks like the hummingbird is getting a pat on the head from the flower.  In this case, the bird is indeed performing a vital service for the plant -- moving pollen from one flower to another.

It looks like the hummingbird is getting a pat on the head from the flower. In this case, the bird is indeed performing a vital service for the plant — moving pollen from one flower to another.

The bill of the Ruby-throated Hummingbird is the perfect size and shape for this flower.  When it dips its bill deep into the base of the flower, the top of its head brushes a fringe of anthers which deposit pollen on the surface of its head feathers.  Later when it visits a different flower, perhaps on a different plant, the pollen will be rubbed against that flower’s stigma, adhering to the sticky surface.  If it is the right type of pollen, it will germinate and a pollen tube will grow down the stalk supporting the stigma (the style) into the ovary. Sperm can then leave the pollen grain, swim down the tube, and fertilize the ova to begin the process of seed production.

The contact between the stigma of the flower and the

The contact between the stigma of the flower and the hummingbird’s head is more obvious in this close-up.

Hummingbirds don’t care which flowers deposit pollen on their head, but the plants want to ensure that a particular flower receives pollen from a different individual (i.e., avoid self-pollination).  To maximize the potential for out-crossing, Cardinal flowers develop the male parts first — promoting pollen donation, and after a few days, the style and stigma emerge to protrude beyond the anthers — promoting pollen reception.

The anthers look like a white fuzzy fringe on the stalk that sits above the petals and the opening of the flower.

The anthers look like a white fuzzy fringe on the end of a gray stalk that sits above the petals and the opening of the flower.  The flower on the left shows the pink stigma just beginning to grow beyond the level of the anthers.  The flower on the right is newer and does not yet have female reproductive parts showing.

A mature Cardinal flower, with the stigma (and style) protruding beyond the anthers.  This stigma could easily pick up pollen from the back of a hummingbird's head.

A mature Cardinal flower, with the stigma (and style) protruding beyond the anthers. This stigma could easily pick up pollen from the back of a hummingbird’s head.

Coevolution of cardinal flower structure and Ruby-throated Hummingbird sugar appetite has made this system a perfect fit for both.

The End.

The End.