Plant Profile: Goldenrods (Solidago sp.)

Right now in prairies, woodlands, roadside ditches and home gardens, wonderful displays of native grasses along with wildflowers blooming yellow, white, and lavender are putting on quite a show. The yellow wildflowers are most likely either sunflowers or goldenrods. Each is quite beautiful and teeming with pollinators.

Solidago ‘Wichita Mountains’ blooming in the Compassionate Friends Garden

Goldenrods are just as diverse and variable as sunflowers. While many landscape plants have already reached their peak and the flowers have faded by September, goldenrods have become the stars of the show as they brighten up the landscape. Their golden yellow autumn inflorescences are striking.

In spite of their attractiveness, goldenrods have a reputation for causing allergies. In truth, this is unlikely, because goldenrod pollen is large and heavy and is not carried by the wind. Rather, it is giant ragweed (Ambrosia sp.) that is spreading pollen through the air at the same time.

These wildflowers are insect-pollinated by many wasps, moths, beetles, honey bees, monarch butterflies and other beneficial pollinators searching for a sip of nectar. In total, 11 specialist bees and 115 different caterpillars need these plants. There are around 50 species of insects with immature forms that feed on the stems of goldenrod. In addition, seeds and foliage provide food for some birds and mammals. Across the board, goldenrods are of huge value to wildlife and one of the keystone wildflowers for pollinators.

Gray Goldenrod-Solidago nemoralis

Goldenrods are adaptable to a wide range of conditions in nature, making them a great choice as a landscape plant. They grow naturally in soils from wet to dry. Even the drought conditions we have been experiencing have not kept these denizens of the prairie from blooming. There is a goldenrod that will grow in your garden.

For all their positive attributes, there are goldenrod species that don’t belong in a formal garden. Canada goldenrod for example is a highly aggressive species that spreads by underground rhizomes and seed, ultimately pushing out other smaller desirable plants. It will take over a garden in a couple of years. However, in a prairie setting with the deep roots of native grasses and competition from other plants, it can be mostly kept in check. That is why we recommend clump-forming goldenrods as a more reliable choice for the landscape relegating those aggressive species to the prairie or outskirts of the landscape (along a fence or in an alley) where they are free to roam and spread.

I like Solidago rigida, Solidago nemoralis, Solidago ‘Wichita Mountains’, Solidago canadensis ‘Golden Baby’, and Solidago ‘Fireworks’ for sunny areas. For shade, I choose to plant Solidago odora, Solidago ulmifolius or Solidago caesia. It is safe to say that goldenrods are powerhouse plants that deserve a place in your native garden.

Rigid Goldenrod-Solidago rigida (top) and gray goldenrod (bottom)
Solidago rugosa ‘Fireworks’

Plant Profile: Letterman’s Narrowleaf Ironweed (Vernonia lettermanii ‘Iron Butterfly’)

In the late summer and early fall, it is a good time to evaluate how your landscape has performed.  What plants have thrived and which plants have disappointed you? I take notes of these plants and plant more of the good ones and fewer of the bad ones. Fall is a great time to plant just about anything and to fill some of those holes in your landscape. I would also think about moving the under-performing plants to a more ideal location. You can move them next March or April.

One of the plants that has done well again this year in the Arboretum is Letterman’s Narrowleaf Ironweed. It is a reliable drought-tolerant wildflower that requires little to no extra irrigation.  In fact, too much water makes it floppy and unhappy. Plants like that are rare and should be utilized more, in my opinion.

Right now, in late August, it is covered with exploding deep purple flowers atop the sturdy upright stems. The narrow leaves whorled around the stem remind me of narrowleaf bluestar (Amsonia hubrichtii) , except these are even more narrow. These leaves combined with the attractive frilly flowers give it a soft, pleasing texture.

Ironweed is named for its tough stem. Iron Butterfly Ironweed is the diminutive cousin of the pasture ironweed. Typical prairie ironweed is coarse and tall, but Letterman’s Narrowleaf ironweed is more refined. The parent species Vernonia lettermanii is quite rare and can be found in Arkansas and Oklahoma.

In late summer, the flowers are just what butterflies and other pollinators need as they migrate or prepare for winter. The flowers are swarmed with all sorts of butterflies, skippers, moths, and bees. In the Arboretum, we plant them in sunny gardens with medium to dry soil. They can take some shade, but have a tendency to flop.

Vernonia lettermannii ‘Iron Butterfly’ is a lovely accent plant for your wildflower garden. It combines well with native grasses such as little bluestem and prairie dropseed.  Black-eyed susans, coneflowers, asters and goldenrods grow in harmony with narrowleaf ironweed.  If you need a tough plant for that scorching hot place in your yard, give it a try. I think you will be pleasantly surprised. We will have this wonderful plant along with many other wildflowers, grasses, shrubs and trees at our fall FloraKansas plant sale.

Vernonia lettermannii ‘Iron Butterfly’ is one of Piet Oudolf’s “Must Have” plants. I agree that it is a garden-worthy plant.