Goldenrod Bunch Gall

Pretty much anywhere you find goldenrod, you can see goldenrod ball galls. These round formations on the stem of the goldenrod plant are winter homes for the larvae of the Goldenrod Gall Fly (Eurosta solidaginis). By this time of the winter, many of the galls have holes excavated by chickadees or woodpeckers, who find the larvae a tasty winter treat. For more on ball galls, see How Galling!

While not quite as common as ball galls, at least around here, goldenrod bunch galls can often be found in patches of goldenrod as well. They are easily identified. They look like flowers with many woody petals set at the tip of the goldenrod stem. Bunch galls are caused by a midge, Rhopalomyla solidaginis, and are associated with a particular species of goldenrod, Solidago canadensis.

The midge lays its egg in a leaf bud. After the larva hatches, the stem stops growing longer, even though the goldenrod continues to produce leaves. This results in a tight, flower-like cluster of foliage at the top of the goldenrod’s main stalk. An assortment of insects, including spiders and other midge species, may make the bunch gall home.

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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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