End of Summer is Bittersweet

In addition to the time of year, one certain aspect of the natural world that determines what plants will grow in an area is the amount of light.  Plants vary a great deal in their need for the amount of light which is expressed as shade tolerance.   This is particularly clear in a forest which has plants such as oaks and hickories which can grow under the canopy or trees such as pines that require an open sunny environment to thrive.   One example of this process is the appearance of a GAP in the forest due to tree fall or removal.  While hiking in Cane Creek mountains I observed such a gap and noticed that it was filled with small sweet gum tree saplings which were not found anywhere else in the shade.   This is one of the earliest trees to appear in a moist field which is allowed to undergo succession and not cut or subject to grazing.

I have to admit that I am in love with flowers of the hibiscus (mallow) family.  For this reason I grow non-native Althea or rose of Sharon.  I prefer the single flowers with a red center which are the wild type and illustrate so well the occurrence of a “nectar guide.”  Many insects have a broader color vision spectrum than we do (extending into the UV and polarized light) but their compound eyes have less visual acuity than we do and they may have trouble quickly finding the center of the flower where nectar and pollen are located.  Thus many flowers have a colored or darker center to cue the insects where to go.  However many hibiscus do not have nectar but only provide pollen rewards for pollinating bees.  I do “dead-head” the flowers so that no seeds are produced.  I also grow the native semi-aquatic red hibiscus which produces nectar but it requires a very moist soil to grow well.

One of the characteristic hummingbird flowers of late summer is the cardinal flower.  You will find it in two natural locations, growing in small wooded stream courses and in wet pastures.  It thrives in such disturbed habitats where competition with other plants is less and it has an advantage in that it is poisonous to mammalian herbivores such as cattle and horses.   It is of course a very specialized tubular flower type that attracts hummingbirds due to its color and nectar, the exact opposite of many asters.

The end of summer of course is marked by the maturation of fruits and these dogwoods are a prime example.  Their numerous flowers only set a limited number of fruits due to abortion and gradually turn red in late August.  Obviously a red fruit will attract birds with color vision although some plants have dark fruits but show red leaves to attract animals to disperse their fruits (black gum, Virginia creeper, etc).  In middle September I will begin to watch carefully for silent avian migrants from the north (Swainson’s and gray cheeked thrushes) that key in on dogwood trees to gobble down the fruits.

This time of year I begin to enjoy the fruits of numerous non-native figs which I have planted.  The Piedmont of N Carolina is very suitable for their growth.  The anatomy of the fruit is quite unusual- it is a “syconium” with numerous small fleshy fruits inside which are pollinated by a specialized tiny wasp ( https://en.wikipedia.org/wiki/Syconium ).  Even if you like figs this may be too much information for your tastes !  These non-native fruits are also quite popular with birds, mammals and insects.

Common milkweed fruits are maturing now and this is a time for appearance of several highly specialized insects that feed on the leaves and seeds.  The plants are drying up now and are of limited attractiveness to monarchs.  If you want to provide food for monarch caterpillars in late summer you must prune/cut the stems in late June to stimulate regrowth of fresh green foliage.  Otherwise the dry foliage is most attractive to milkweed tussock moth caterpillars which will quickly defoliate the plants.  As the seed pods swell up, a host of seed predators such as the large milkweed bug will appear first as nymphs.  Then they will mature into adult bugs with bright red colors to advertise their noxious nature due to feeding on the milkweed toxins.

Butterflies are still quite numerous, the most common being the beautiful yellow and black tiger swallowtail.  There are fewer of the striking black female morph which mimics the toxic pipevine swallowtail.  The zebra swallowtail is an extraordinary color/pattern with very long “tails.”  Its food plant (paw paw) is quite common down along the river but it is never very abundant.  I have seen just a few monarchs- in this case a female is finding nectar on a non-native Mexican sunflower or Tithonia with an extraordinary orange color.  Note that the inner and outer wings are both brightly colored to advertise the toxicity of the monarch derived from the milkweed food of the caterpillar.  This is different from many other butterflies which have bright inner wings and cryptic outer wing surfaces to camouflage them when resting.

August is the time of spiders as many grow rapidly and mature into adult females which mate and lay their eggs before dying.  The strangely named rabid wolf spider is often seen roaming around on the ground, hunting without a web.  The amazingly camouflaged green lynx spider is found lurking in flowers and pouncing on unwary insects.  I found this rarely seen but remarkably healthy black shouldered spinyleg dragonfly in the web of a golden garden spider and released it- the spider was feeding on a tiger swallowtail at the time.  Look at this huge tarantula found by my son Bill Jr while running in the mountains near Salt Lake City- now that would give you arachnophobia for sure!

Birds are considerably less obvious in August since most stop singing after breeding is over.  I noticed this adult bald eagle down along the river several times- obviously here for the easy fishing.  I occasionally get lucky and see some of the local breeding warblers at my dripping water bath.  This prothonotary warbler breeds nearby in the floodplain but is rarely seen.  The yellow throated warbler breeds in tall pines next to my house and comes daily to the water for a bath.  Hummingbirds are regular daily visitors to my flowers- mainly coral honeysuckles and butterfly bushes.

I used to wonder if deer would cross the river at low water and here is the answer.  This deer seems quite content in the water and in fact may be feeding on something.

Nothing in life is more guaranteed than change and the regular passage of the seasons is no different.  Certainly a naturalist can never be bored with the changing cast of plants and animals that pass by us all the time.  As Fall approaches we are about to witness the amazing process of migration, so buckle your seat belts and enjoy the ride!