Richard Bogren, Gill, Daniel J. | 9/21/2017 7:17:42 PM
By Dan Gill
LSU AgCenter Horticulturist
(09/22/17) You can almost always find some Louisiana wildflowers blooming throughout the year. The spring and fall seasons, however, are when the most outstanding displays occur.
The fall wildflower season is just getting underway now and will continue through the end of November. The major colors of the fall display are golden yellow, purple, lavender, blue and pink.
Particularly noticeable are tall wildflowers. I already see the royal purple flowers of tall ironweed (Vernonia altissima) towering above surrounding plants. This dramatic wildflower is a perennial that lives and blooms for a number of years. It is beautiful enough to be used as a late-summer- and fall-blooming garden plant. I’ve used it effectively in beds with old garden roses, where the purple combines beautifully with the roses’ scarlet, burgundy, pink and white flowers.
Also notable are large bushes of American beauty berry (Callicarpa americana). Rather than flowers, these plants are known for their showy clusters of red-purple berries along the stems. This native, deciduous shrub is easy to grow in full sun to part shade. You may find plants at area nurseries, or they can be ordered from mail-order nurseries on the internet.
Goldenrods (Solidago sp.) are another group of tall-growing wildflowers. The bright golden yellow flowers are showy and make great cut flowers. By the way, goldenrods do not cause allergy problems this time of the year. Goldenrods are insect pollinated and produce heavy, sticky pollen.
It is the wind pollinated plants that dump pollen into the air in vast quantities and stimulate allergies this time of year. The flowers of wind-pollinated plants are small and insignificant because they do not have to attract insects. The main culprit for fall allergies is giant ragweed (Ambrosia trifida), not goldenrod.
The narrow-leafed sunflower (Helianthus angustifolius) blooms in October and November and is among the showiest of the fall wildflowers. Bright golden yellow daisy-like flowers with dark centers are produced in great quantity by tall plants. In naturalistic landscapes, it is an outstanding addition to low, wet areas.
Filling in below the taller plants are colorful wildflowers such as the blue mistflower (Conoclinium coelestinum). The lavender blue color of the flowers provides a beautiful contrast to all of the gold-flowered wildflowers. I use this perennial wildflower in flower beds.
Other wildflowers you may see include white, lavender and pink asters (Asters sp.), golden yellow sneezeweed (Helenium autumnale) and purple blazing star (Liatris sp.). Lavish displays of these fall wildflowers along with many others make a feast for the eyes for those who will notice.
Gardeners who may struggle to create beautiful displays of flowers in their own landscapes marvel at the way nature seems to achieve such beauty without effort. This may lead gardeners to wonder if they could create a similar effect in their own landscape.
Actually, you can. Fall is a great time to plant wildflower seeds that will produce a colorful display next spring and early summer. In some landscapes, natural-looking areas of wildflowers would be very appropriate. The wild, untamed look of these plants is entirely appropriate in casual, informal landscape designs.
Although the look you are trying to achieve may be spontaneous and natural, growing wildflowers requires planning. Look carefully at the growing conditions in the area where you want to plant wildflowers. You must use the wildflowers that will thrive under those conditions if you expect success. Note especially how much sun the area receives, the texture of the soil and whether the area tends to be damp or dry. You can find wildflowers that can be grown in virtually every environment with proper selection.
Based on the growing conditions in your site, choose a theme for your wildflower garden. Open, sunny areas are perfect for a field or meadow planting. Wildflowers in open areas along highways are typical of this type of planting. A shady woodland setting requires a different set of wildflower species. Even boggy, damp areas can make appropriate wildflower gardens if the proper plants are used.
The easiest type of wildflower garden to establish is the open-field type grown from seed. Fall planting of seeds tends to produce the best results and should be done in late October through November. Spring planting may also be done in late February, but it’s not as good as a fall planting.
Select a sunny area to be planted and eliminate existing vegetation such as aggressive grasses by hand removal or using glyphosate herbicide (Killzall, Roundup, Eraser and other brands). Wildflower seeds will not germinate well in an area with established, thick vegetation. Generally, no fertilizer or soil amendments should be added to the soil during preparation.
For a small planting, mix the wildflower seeds with sand or sandy soil and broadcast them evenly over the area by hand. Make sure you use seeds or seed mixes of species that do well in our state. Provide good seed contact with the soil, if practical, by pressing the seed into the soil with a board or roller.
The seeds should be watered occasionally if the weather is dry. But rainy winter weather generally makes watering unnecessary. Look forward to an abundant display in spring and early summer.
Goldenrod (Solidago altissima) attracts pollinators to the fall landscape. Photo by Dan Gill/LSU AgCenter
The royal purple flowers of tall ironweed (Vernonia altissima) can tower above surrounding plants. Photo by Dan Gill/LSU AgCenter