Tuesday, August 24, 2010

Goldenrod and Ragweed

Closeup of the flower of Common Goldenrod, Solidago canadensis Picture courtesy of Annette MaCoy
Cumberland County home horticulture educator
Goldenrod, or Solidago canadensis, a native perennial, is often blamed for causing misery for allergy sufferers this time of year. The real culprit, however, is ragweed, or Ambrosia artemisiifolia, a summer annual. Allergies are caused by small pollen grains from plants and trees that use the wind to spread them over a wide area. The plant’s reproductive survival is based on these wind-blown pollen grains happening to fall on another flower of the same species of plant or tree located elsewhere. The chance of successful fertilization is increased by producing a huge quantity of small, light, pollen grains, which can carry over great distances.
Field of blooming Common Goldenrod, Solidago canadensis
Picture courtesy of Annette MaCoy
Cumberland County home horticulture educator
Unfortunately for us, that also means that we can breathe them in, causing an immune system response that results in the familiar symptoms of sneezing, running nose, and headaches that make outdoor activities difficult for allergy sufferers. Goldenrod, however, is a flowering plant that uses insects to spread its pollen around. These grains are larger and heavier, and produced in much smaller quantities. Goldenrod gets the blame, simply because they are far more visible and blooming at the same time that the inconspicuous flowers of ragweed are also blooming. The native, wild species of goldenrod are also somewhat aggressive, spreading both vegetatively and via seed and can be considered weedy by home gardeners and farmers. They do, however, provide a welcome late summer and fall nectar and pollen source for beneficial insects and pollinating bees, that make them a desirable plant to have around.


Closeup of the flower of Common Ragweed,  Ambrosia artemisiifolia
Picture courtesy of Annette MaCoy
Cumberland County home horticulture educator
Fortunately, plant breeders and hybridizers (mostly from Europe) have developed Solidago cultivars that are smaller and less aggressive, making them attractive additions to a home landscape, with the added benefit of providing a food source for the good bugs.  The European cut flower industry has also recognized their attributes and they are increasingly used in arrangements, especially for cemetaries.

Common Ragweed, Ambrosia artemisiifolia Picture courtesy of  Annette MaCoy
Cumberland County home horticulture educator

So, keep ripping out any instances of ragweed that you find, to reduce the amount of pollen in the air, and consider adding some goldenrod to your landscape.

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