To the Goldenrod
Lower that glad Summer gleams with charm indue,
With conjuring rods evoking saffron dyes,
To vest nude hills in joy of hue,
To paint with cheer the vale’s sad view,
And point above to freedom’s sapphire skies-
Our Nation’s beams now summon thee,
For growth of liberty aglow to stand,
Her figured strength in bloom to be-
In garlands sun-wrought for the free,
An aureate ensign on her golden land!
Henry O’Meara-Ballads of America
During the late summer and early autumn one of the most dominant landscape features in New England are old fields dominated by the blistering yellow color of our native goldenrods. Many a photographer has tried to capture pastoral scenes of these yellow fields, bordered by bright fall foliage, next to a treasured red New England barn.
The goldenrod plant has a bad and undeserved reputation in that it is often associated with hay fever and allergies. The pollen from goldenrod is far too heavy to be carried by the wind and therefore it is not responsible for these nasty ailments. Unfortunately it blooms at the same time as ragweed that has a very light and wind borne pollen. The ragweed pollen distribution is the true cause of these maladies.
New England is blessed with many types of goldenrod. Tall goldenrod, late goldenrod, Canada goldenrod, rough-stemmed goldenrod, Elliot’s goldenrod, and swamp goldenrod are a few of the goldenrod species common to our area. Each goldenrod has its own individual preference for where it grows. Some goldenrods grow in wet soils and some in dry soils, some like a little shade and some like full sun.
Goldenrods tend to dominate old agricultural fields to the point where few other plants can grow in these areas with any great success. This happens for two reasons: first, the goldenrod plant is allelopathic meaning it emits chemicals into the soil to prohibit other plants from growing. Walnut trees and Norway maple trees are examples of two other allelopathic plants. Goldenrods emit phenol into the soil, a very effective chemical to eliminate or discourage most, but not all, other plants from growing. The second reason goldenrods dominate old fields is because they are clonal, meaning they spread voraciously by underground rhizomes and by heavy seed production. The goldenrods growing from rhizomes form plants that are genetically identical to the parent plant.
Goldenrods can be hosts to the stem gall-fly. These insects use the goldenrod for reproduction and incubation. After mating the female stem gall-fly utilizes a special adaptive body part called an ovipositor to inject the goldenrod stem with chemicals that cause rapid cell division in the plant stem. This cancerous growth caused by the chemical deposition forms a gall in about three weeks after the injection. This gall appears on the stem as an ovate structure, usually 3-4 times the normal stem diameter. Eggs are deposited in the same area simultaneously. The gall has a hull that is comprised of a cork like material. The inner part of the gall is comprised of plant tissues that provide nutrition to the fly larvae.
While the gall grows the eggs hatch and the larvae excavates a central living chamber within the gall. The larvae will remain in the gall until the following spring. The larvae actually excavate an exit tunnel for use the following spring.
Interestingly, the same species of stem gall-fly will utilize different types of goldenrod. Offspring of the gall-fly parent will only utilize the same species of goldenrod. This is an interesting survival tool in that it encourages evolution of the species by isolating individual species so that the overall species does not become quickly homogenized. This allows individual groups within a species to evolve along different pathways and therefore increase the chances of survival to diseases and environmental circumstances to which they may become exposed. Amongst most animal species this “speciation” occurs because of geographic isolation. The stem gall-fly can accomplish this same principal within the same field by utilizing several different species of goldenrod on which they form the galls. There is also new research that indicates some stem gall flies will only make galls on clonal plants that are genetically identical to a parent plant on which their formative galls were located.
The secret life of the goldenrod plot thickens as the gall-fly wasp comes onto the scene. There are several different species of wasp that predate the stem gall-fly. Each has a slighty different strategy for taking advantage of the gall-fly. One of the more common wasps penetrates a developed goldenrod gall with its own ovipositor and inserts fertilized wasp eggs. The larva that develops from these eggs first feeds on the stem gall fly larvae and then utilizes the nutritive value of the gall’s interior to survive the winter months.
In the natural world, each plant has its own ecological and evolutionary story. Some are obvious and some are not. As with many plants, the goldenrod has complexities that ecologists and botanists are still trying to understand. Some of these mysteries can be beneficial to humankind. For example, medical scientists have studied the chemical secretions emited by the stem gall-fly that cause the rapid cell division in the goldenrod stem in an effort to better understand cancerous rapid cell division in animals.
Goldenrods are some of our most common plants. They are easily recognized, yet they hold secrets that may not be obvious to the causal observer. As we attempt to unravel the secret life of the goldenrod we can hope to make discoveries that will not only improve the human condition but also gain a better understanding of the mysteries of the natural world around us.
Originally written for the Heath Herald in 2001.