Sunday, August 14, 2011

Late Summer Yellows

Late summer brings out an incredible amount of yellow blooms in the native garden.  Many of these yellow-blooming plants are members of the Asteraceae family, also known as Compositae.  If you’ve ever heard someone mention the acronym “DYC”, these are the flowers they mean – as in “damn yellow composites” – because there are so many of them, they look a lot alike, and they hybridize among themselves to create new forms.

Annual Sunflower, Helianthus annus

Composite flowers are usually composed of both disk and ray flowers – and a lot of them. What you consider "a"  flower is actually many flowers in an arrangement.  The disk flowers are tiny flowers located at the center of the structure while the ray flowers are what many folks consider to be the “petals”.  Here is a very good site that explains and provides more examples of these terms.

Coreopsis major

Probably the first of these to bloom in my area is the large flowered Coreopsis, Coreopsis major.  It’s a great plant, hardy and tough as the dickens.  However, I find the flowers extremely hard to photograph because they don’t always look so good when you get close up (but you can see I found one here)!  Still, I would recommend them because they are fine with poor soil and dry conditions.  The whorled foliage is very attractive from spring to fall.

I will cover the next three genera alphabetically because it is hard to say which starts blooming first: Helianthus, Rudbeckia or Silphium.

Helianthus angustifolius
Helianthus divaricatus

The genus Helianthus is generally known as the Sunflower family.  The annual sunflower, Helianthus annus, is a member, but there are many other species that are perennial garden favorites.  The woodland sunflower, Helianthus divaricatus, is a stoloniferous plant which means that it grows by underground roots to make expanding colonies.  In rich and moist garden soil that means it will be a bit aggressive.  It normally grows on dry, partially shaded woodland edges.  

Taller members of this genus include Helianthus tuberosus, which is known as Jerusalem artichoke (at least you can eat it if it gets too aggressive!), and Helianthus angustifolius, the late blooming swamp sunflower.  I have seen majestic stands of swamp sunflower blooming in gardens in October – the statuesque clumps are much admired by those that pass by.

The flowers in the genus Rudbeckia are known as coneflowers.  One of the most commonly sold forms is Rudbeckia fulgida ‘Goldsturm’ and is usually referred to as Black-eyed Susan.  I have (and enjoy) another form known as Rudbeckia fulgida var. fulgida which is often known as Orange Coneflower.  I used to think this was a later blooming form – now I know that it is late for me because the deer keep eating it in spring and summer!  But that means I get a lot of blooms eventually due to all that “pruning”.  

Rudbeckia fulgida ‘Goldsturm’

The one that many folks consider to be the “original” Black-eyed Susan is Rudbeckia hirta which is considered to be short lived perennial (but reseeds nicely).  It is easily distinguished from Rudbeckia fulgida because the plant parts (stems and leaves) have many hairs.  It is one of my favorites, and I love to see it growing on roadsides and in fields this time of year.  A similar, but taller, species is Rudbeckia triloba, which is sometimes called Brown-eyed Susan.  Some of the leaves have 3 lobes which helps to distinguish it from R. hirta in the field.  Tired of the dark eyes?  Not all the coneflowers have them.  Cut-leaved coneflower, Rudbeckia laciniata, has greenish cones.  There is also the yellow-flowring genus Ratibida which shares the common name coneflower with Rudbeckia.  I know that many people think that using the Latin name is unnecessary, but you can see here that common names can mean different plants!

Rudbeckia hirta

Rudbeckia triloba

Another genus with great height is Silphium, known as “rosinweed”.  Probably one of the most well known members of this genus is Cup Plant, Silphium perfoliatum (also known as Silphium connatum).  The stem pierces the leaves, creating a “cup” at the junction.  This cup can fill up with rainwater, allowing birds to drink from it.  Kidney-leaf rosinweed (Silphium compositum) is often found in my area.  I find the leaves to be quite beautiful – thick, sculpted, and decorated with red veins.  In late July I attended the Cullowhee Native Plant conference, and several vendors had Silphium integrifolium for sale.  Members of this genus deserve more use in the garden – they are dependable and drought tolerant perennials for late summer blooms.

Silphium compositum

Silphium compositum, foliage

Silphium perfoliatum, Cup Plant
Photo by M. Tucker

Silphium perfoliatum

Confused by all these disk and ray flowers?  Looking at the BACK of the flower may be helpful.  The green bracts which hold the flower can be very distinctive.  Here are pictures of the back of the flowers discussed above.

Rudbeckia back
Helianthus back

Coreopsis back

Silphium back

Another tall yellow flower blooming now is Smallanthus uvedalius, known as Bear's foot because of the leaf shape.  I photographed this last week on a roadside.

Smallanthus uvedalius
Smallanthus back

Other yellow flowers that you may see this time of year: St. John’s Wort (Hypericum, which is usually a type of shrub), Goldenrod (Solidago altissima is probably the most common one on roadsides), Bidens (known as tickseed for the shape of its seeds), Maryland aster (Chrysopsis mariana), Wing-stem (Verbesina alternifolia or V. occidentalis) and Silk grass (Pityopsis graminifolia).

Hypericum punctatum
Solidago altissima
Pityopsis graminifolia
I hope to do a full blog entry on just Solidago soon.  I think it is a genus that is under-appreciated.  In the meantime, enjoy the many ways that yellow appears in our summer roadsides.


  1. Ellen,
    You are so right about all the yellow flowering natives right now. I love this time of year. My stiff goldenrod is just starting to flower and it seems to attract the most diverse set of insects.

  2. How does Helenium fit into all this?

  3. Helenium should be right in there too! In fact today I saw a big group of Helenium autumnale at a State Park but I didn't have my camera. It was a cheerful site and not bothered at all by the lack of rain lately in the area.

  4. The name 'helenium' is ascribed to Helen of Troy, who cried for some reason and her tears allowed the plants to prosper. Not to sun as I had originally thought.
    Now we get to something I read this morning:
    Heliotropium, nothing to do with sunflowers, stands for helios=sun and trope=to turn.
    In other words, the same as 'tourne-sol' which leads back to sunflower again.
    Names are confusing, even the Latin ones.

    What you consider wildflowers, are often our prized herbaceous plants. I have to admit to a certain amount of envy.

  5. Yes, I have heard that some of our wildflowers are favorites in Europe and that some of the best cultivars come back to us from breeding programs outside of the US. I am glad they are appreciated there and I hope the feeling will catch on here one day.

    I love living in a semi-rural area where I can see many of these on the roadsides - I can only imagine how beautiful this land was several hundred years ago, full of color and critters!