Extension Educator, Horticulture
Goldenrod is the "Rodney Dangerfield" of the plant world. It gets no respect. Could be it is just too common since some species are found growing in ditch banks or it maybe its lovelessness is due to its misguided association with hay fever. Ragweed that blooms at the same time as goldenrod is the actual culprit in hay fever problems.
I hear the snorts of stuffy nosed doubters, so let's look at both plants. Goldenrod has showy yellow flowers to attract its insect pollinators. Its pollen is heavy and sticky so it will cling to the insects for a ride to the next flower so pollination will occur. Heavy sticky pollen does not blow well in the wind or up your nose. However, ragweed has homely green flowers and relies on wind pollination. Ragweed overwhelms the air with lightweight pollen in the hopes it will land on another ragweed flower. The take home lesson is: if you have allergy problems beware of the stealth green flowers that rely on wind pollination.
Goldenrod is an excellent garden perennial that is much more beloved in Europe than in its homeland of North America. Its bloom time varies with the species, but is usually late summer to early fall. Plant heights vary from 1-6 feet tall.
In their native areas goldenrods may be found growing in prairies, woodlands and bogs. However most goldenrods grow best in full sun to very light shade in well drained soil of average to low fertility. Too much fertility causes the plant to get very tall and floppy. Once established, they are quite drought resistant. Goldenrods also attract beneficial insects and butterflies.
In the garden the clump forming goldenrods are preferable to the ones spreading by rhizomes. The rhizomatous types can be real thugs in a garden as they trample any plant in their path. Cultivars to look for include:
'Golden Baby' (grows two feet tall with golden yellow plumes) and 'Cloth of Gold' (18 to 24 inches tall with dense, deep yellow flowers).
One of my favorites is Solidago rugosa 'Fireworks.' It has tiny yellow flowers on arching stems. As the name implies it looks just like fireworks. 'Fireworks' is almost shrub-like with its sturdy stems and tight crown. The small leaves emerge burgundy in spring then turn dark green in summer. 'Fireworks'blooms are exploding now in the Master Gardener Idea Garden.
'Baby Sun,' 'Baby Gold' and 'Goldkind' are nice upright hybrids at two and half feet tall, although they need deadheading to remove the distracting brown seed head. Variegated goldenrod, Solidago flexicaulis 'Variegata' has gold mottled leaves to present a color show well before the flowers.
'Golden Fleece' has a long bloom period well into October.
Our native prairie rigid goldenrod, Solidago rigida, is an excellent clump forming goldenrod with rounded gray-green leaves. The flowers aren't as showy as some other goldenrods, but the leaves add a nice contrast to the garden. Rigid goldenrod can get five feet tall in a garden and flop over on all its neighbors. Cutting it back by one half in June reduces the height and makes for more compact growth.
Goldenrods are sometimes plagued with two diseases, powdery mildew and rust. Good air circulation around the plants may help, but look for resistant cultivars such as the ones listed above to avoid problems.
Check out the goldenrods and other late blooming flowers at the Master Gardeners Idea Garden at the U of I Arboretum on south Lincoln Avenue in Urbana. On Saturday, September 15 at 10:00 am join the Master Gardeners for a program on caring and selecting roses. On September 22, at 10:00 am the Master Gardeners will share their suggestions for great tools to use in the garden.