Goldenrod and Asters

Summer’s last refrain is sung by goldenrod and asters. Like one last hurrah, goldenrod and asters delight the late-season pollinators and please the eye with their blaze of purple and gold.

There are a few species of goldenrod native to the northeast of the continent, but one of the most common is Canada Goldenrod (Solidago canadensis). It’s bright, showy flowers bloom in clusters along the ends of arching branches.

Goldenrod is often blamed for causing hay fever, but its pollen is too heavy to be wind-borne. Instead, it relies on insects such as the bee in the opening photo to carry its pollen from flower to flower. Hayfever is caused by plants that are wind-pollinated, such as ragweed. As they don’t need to attract insects, flowers on wind-pollinated plants are often inconspicuous.

Patches of goldenrod can be very old. If undisturbed, a goldenrod colony can reach 100 years of age and more. That’s because goldenrod sends out long, creeping rhizomes from the base of its stem. A circle of new plants may spring up around a pioneer seedling. Rhizome production begins after the first year of seedling development. Shoots emerge from rhizomes in the spring, around mid-April.

After the yellow flowers are finished, goldenrod takes on a wooly appearance as the dried seed heads take over.

Goldenrod is popular with insects. One insect commonly associated with goldenrod is the Pennsylvania Leatherwing (Chauliognathus pennsylvanicus), which you can see here. An insect that uses goldenrod as its winter home is the goldenrod gall fly (Eurosta solidaginis), a member of the fruit fly family, along with the well-known pest, the Mediteranean fruit fly. [The flies that buzz around fruit on your counter are actually vinegar flies, or Drosophila.] The goldenrod gall fly overwinters as a larva inside a round gall on the goldenrod stem. For more about galls, visit this post from March. The galls represent both next year’s fly population in the making, and a winter food supply for birds.

Goldenrod is a member of the aster family. There are many species of asters, but one of the best known is the New England aster (Aster novae-angliae). Its compound flower head features yellow central disk florets surrounded by purple-blue ray florets.

The genus name Aster means star. It is certainly a star in the late-summer meadow. New England aster can be differentiated from the similar fringed aster (Aster ciliolatus) by its leaves, which are long and narrow, while those of the fringed aster are heart-shaped.

Native plants are always a good choice for the home garden and there are a number of native varieties and hybrids of both solidago and asters available. Solidago “Little Lemon” is a short hybrid, just 12 inches tall, appropriate for the front of the garden. Solidago rugosa “Fireworks” reaches about 40 inches and features an upright, bushy habit and large heads of golden flowers. Some of the cultivars of New England aster include “Purple Dome” and “September Ruby“.

Below, a Cabbage White (Pieris rapae) butterfly visits a New England aster.

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Two Giants

There are two varieties of plants around the edge of the garden and in the fields here that have been growing and growing and growing all summer. I have been waiting all season to see how tall they would get. Both have produced stalks nine feet tall and more. When Birdgirl was here last, I pointed them out to her and she got out the guides and searched out their identity. The first, shown towering above a stand of garden escapees, is Giant, or Great Ragweed (Ambrosia trifida).

There is lots of ragweed around here, and now giant ragweed as well, it seems. Hmm. No wonder my nose is always running. Ragweed is a common cause of hayfever (not goldenrod, which is often blamed). The leaves of the giant variety are quite distinctive, being large and tri-lobed.

Ragweed flowers aren’t much to look at, but they are interesting to read about. There are male and female flowers, with the male flowers positioned on short stalks along the ends of the stems. The female flowers are located below them where leaves meet the main stem. You can see some really great closeup shots of the flowers here.

Here is a sample of the other plant. I uprooted this plant and laid it out on the ground to get an accurate measurement. Nine feet.
It’s Wild Lettuce (Lactuca sp.). It is possibly Tall Blue Lettuce (Lactuca biennis), although one guide observes that due to the large amount of variation in this genus, it is often difficult to identify wild lettuce to the species level.

The genus name, Lactuca, comes from the latin word lac, meaning milk, and refers to the milky sap that the plants release when the stem is broken. The juice of lettuce plants contains narcotic components. Lettuce sap was once used to produce an opium-like substance. However, wild blue lettuce is not one of the more potent species. The leaves are deeply lobed and similar to big dandelion leaves. Below are the flowers, which top the tall stalk.

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