What’s causing your hay fever?
Unfortunately, goldenrods share their bloom time with the inconspicuous ragweeds.
Ragweed pollen is the culprit that aggravates so many hay-fever and allergy sufferers because ragweed pollen is wind dispersed. Ragweeds (Ambrosia spp.) have greenish flowers on tall spikes that are not showy for attracting pollinating insects. They rely on their pollen to be wind-blown to female flowers on nearby plants for their seed production.
Goldenrods have a sticker and heavier pollen that has been adapted for insect pollination. The bright goldenrod flowers attract pollen gathering insects such as beetles. Butterflies, wasps, and bees.
Ragweeds and goldenrods have several differences in plant structure, leaf shape, and plant longevity. Goldenrods are perennials, which are typically single-stemmed or somewhat branched near the top of the plant. Ragweed plants are annuals and are highly branched from the bottom upward. Goldenrods have foliage that is not divided or dissected like ragweed.
There are two species of ragweed that occur in South Carolina, common ragweed (Ambrosia artemisiifolia) and giant ragweed (A. trifida). Common ragweed is more prevalent among the two and has purplish branching stems and highly dissected leaves. These plants grow to about 4-6 feet tall. Giant ragweed has leaves that are dissected into only three parts and can grow 6-8 feet tall. Both ragweed species have greenish, staminate (male) flowers on spikes at the top of each branch.
There are about 28 species of goldenrods (Soldiago spp.) in South Carolina, which all produce bright, golden flowers. Blooming begins in mid to late August and lasts until early October. The Native American’s referred goldenrod as “Sun Medicine” because of its bright color and medicinal qualities. Their flower pigments have also been used to dye yarn. Many new cultivars of goldenrods have appeared in the nursery trade. Governor Mark Sandford signed legislation making tall goldenrod the official South Carolina state wildflower in 2003. If you are looking for shorter and showier goldenrods that spread less aggressively that most species of goldenrods, try ‘Fireworks’, ‘Solar Cascade’, ‘Golden Fleece’, ‘Lynn Lowery’, and ‘Gold Rush’ in your sunny perennial garden.
Some gardeners may want to remove any ragweed plants from their property before they begin making pollen. Ragweed can cause dermatitis or rash if handled without gloves. Continued mowing can also prevent the pollen-releasing flower heads from forming. Initially apply glyphosate for ragweed control. Better control is obtained when the plants are less than 12 inches tall. Follow label directions to make a 1% solution of glyphosate. If additional spray applications are required, reapply at 3-4 weeks after the initial application. Do not allow glyphosate spray to get on desirable plants. Other herbicides may also be used to control ragweed, but if the treated area will be in a vegetable garden or ornamental bed, glyphosate is the safest to use. Other herbicides may harm the planted vegetable or ornamentals plants. Examples of glyphosate produces in homeowner sizes include: Roundup Original, Martin’s Eraser Systemic Weed & Grass Killer, Tiger Brand Quick Kill Grass & Weed Killer, Ultra Kill Weed & Grass Killer Concentrate, Ace Concentrate Weed & Grass Killer, Bonide Kleen-up Grass & Weed Killer, Gordon’s Groundwork Concentrate 50% Super Weed & Grass Killer, Monterey Remuda Full Strength 41% Glyphosate, Hi-Yield Super Concentrate Killzall Weed & Grass Killer, Southern States Grass & Weed Killer Concentrate, Zep Enforcer Weed Defeat III, and Eliminator Weed & Grass Killer Super Concentrate.
For more information on ragweed or goldenrod, please visit the Home and Garden Information Center website at hgic.clemson.edu. Tune in on Tuesday nights to watch “Making it Grow” at 7pm on SCETV or mig.org. Email Outen at callenb@clemson.edu.
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