By Cindy Gilberg
After the floral abundance of spring comes a steadily changing profusion of blooms. The crescendo builds as summer progresses and then, in late summer, both sun and shade gardens become punctuated by the butter yellow goldenrod flowers that blend so harmoniously with the blue asters.
Goldenrods are among the hardiest of perennials for our region. Why, then, do goldenrods get a bum rap? Most times when I discuss the garden merits of goldenrod, there will be a pause and then the all too familiar question, “But don’t they cause hayfever?” The answer is no. Ragweed is the culprit.
Goldenrods (Solidago sp.) have a bloom time spanning August through October, which coincides with the blooming of ragweed. The showy yellow flowers of goldenrod are insect pollinated, attracting a wide variety of insects that are stocking up on nectar and pollen before the winter months set in. Goldenrod pollen is heavy and therefore travels only with the insects that visit it. Ragweed, on the other hand, is wind pollinated. By necessity its pollen is very light weight and abundant, traveling far and wide on the wind currents.
Looking for late summer color to brighten your shade garden? The gracefully arching stems of the blue-stemmed goldenrod (S. caesia) or the compact broadleaf goldenrod (S. flexicaulis) are both welcome additions. Both grow to a height of two to three feet and are good choices for average to dry shade. A mixed planting with Christmas fern and the spring-blooming ground cover Senecio obovatus provides good textural contrast. Other companions for late color are the hoary skullcap (Scuttelaria incana) or the blue zigzag spiderwort (Tradescantia subaspera). Many late-blooming native asters are also shade tolerant such as Aster patens or Aster linariifolius.
One of my favorite goldenrods is the cliff goldenrod (S. drummondii) because of its adaptability to both sun and shade. Its arching habit keeps it from becoming too tall and is perfect for slopes, amongst stones or draping over the top of a wall.
Full sun gardens provide the opportunity for late summer gold with the showy goldenrod (S. speciosa) and the stiff goldenrod (S. rigida). Both stand tall (3′-5′) and are incredibly full of both flower and visiting pollinators when in bloom. Any of the sun loving asters are exceptional complements to goldenrods. In addition, try grouping them with blazing stars (Liatris), rattlesnake master (Eryngium yuccifolium) and some of the native grasses such as little bluestem (Schizachyrium scoparium).
While most goldenrods are incredibly drought resistant swamp goldenrod, (S. patula) loves wet areas in the landscape. It is a great candidate for late summer color in rain gardens or other areas with drainage problems. Let it provide a tall (4′-6′) vertical accent among other moisture-loving plants such as copper iris (Iris fulva), blue mist flower (Eupatorium coelistinum) or purple New England aster (Aster novae-angliae) and red cardinal flower.
So – go for the gold and try some goldenrods. They are exceptionally easy to grow and do quite well with an average soil. Don’t beef up your soil with too much compost or fertilizer! An excess of compost and you will end up with giant versions that tend to flop over. While it certainly is not necessary, some gardeners like to tip prune goldenrods in late May to encourage a better branched plant with a shorter growth habit.
Cindy Gilberg, horticulturist and Missouri native, founded and ran the garden center at Gilberg Perennial Farms with her husband Doug for 28 years, also teaching classes and workshops on gardening and garden design. She now focuses on garden design, consulting and teaching, and also works part-time in the Whitmire Wildflower Garden at Shaw Nature Reserve, emphasizing the use of native plants in home landscaping.