Wildflower is published quarterly by the Wildflower Center. Its content is national in scope with articles about the conservation and use of native plants as well as news from the Wildflower Center. A subscription is provided to Wildflower Center members as a benefit of membership.
Autumn Blossoms by Lisa Halvorsen - Fall 2003
Native wildflowers add interest and beauty to the autumn landscape. While a greater number of wildflowers bloom in spring and summer, by selecting those that flower later in the year, you can create an attractive, colorful garden that rivals the rich profusion of blooms of early-season and summer gardens.
It is possible to alter growing conditions, such as soil pH, to make your site more receptive to a particular species, but you'll have greater success if you choose plants that are native to your area and suited to existing growing conditions and climate. Native wildflowers appropriate for a Southwest desert garden will not grow well in the cooler, moist climate of the Pacific Northwest or the humid subtropics of the South.
As with any planting, start with a good seedbed. Prepare the soil for planting by raking out plant debris and rocks to create a smooth surface for planting.
If direct-seeding, broadcast the seed uniformly over the seedbed. Push the seeds into the soil firmly and then cover with a thin layer of straw. Adding fertilizer generally will not benefit the plants and may cause excess vegetation growth instead of the desired flowers. Water gently. Adequate moisture is one of the most critical factors in encouraging germination and establishment of seedlings.
In all parts of the country, seeds can be sown in the late summer and fall for blooms the following year. In the Northwest, Midwest, and Northeast, fall-seeded wildflowers will remain dormant until the following spring. The colder winter months help break the dormancy cycle, ensuring a higher germination rate for seeds sown now instead of in the spring. In the Southwest and Southeast, seeds usually germinate and become established before winter arrives.
Generally, container-grown wildflowers that bloom late in the year should be transplanted in the spring for best results. Species that flower in late spring and summer, including those that continue to bloom into September and October, can be planted either in the spring or fall with equal success.
Although all of the wildflowers listed below have a wide geographic distribution within the region, each has specific requirements for soil, light, and moisture. Before purchasing, check with your local nursery or garden center to ensure that the plants you select will grow well in your location.
The moist, open woodlands common throughout much of the Pacific Northwest host a number of native wildflowers with fall interest, including yellow willowherb (Epilobium luteum), great northern aster (Canadanthus modestus), and wild ginger (Asarum caudatum).
Yellow willowherb is an upright, bushy wildflower with slender stalks and numerous finely toothed alternate leaves each about 3 inches long. Its leaf shape is lanceolate (narrow, pointed at each end) to ovate (egg-shaped). The 4-petaled creamy-yellow flowers grow singly from the upper leaf axils on a plant that grows from 6 to 28 inches high. The native range of yellow willowherb is from Alaska south to Vancouver Island, Oregon, Washington, and parts of California.
The great northern aster has large, leafy, purplish-red flowers and smooth, lance-shaped leaves. It may grow 1 to 3 feet tall. For a bushier plant, cut it back to half its height in late spring. This plant occurs in the wild in moist environments, including stream banks, forest edges, and clearings from Alaska south to Washington and Oregon and east to Alberta, Idaho, and Montana. This plant actually occurs throughout Canada, though less in the east. It also occurs infrequently in Minnesota and Michigan.
Wild ginger grows 5 to 7 inches tall with a spread of 12 to 14 inches. Although it produces interesting reddish-brown to greenish-yellow flowers in spring and summer, this plant makes a nice addition to the fall garden for its broad, cordate (heart-shaped), and glossy green leaves that hug the ground and its aromatic lemon-ginger scent. Its native habitat includes British Columbia to central California and east to western Montana.
The striking reds, oranges, and golds of fall-blooming wildflowers add splashes of color to the red-rock palette of the desert country of the American Southwest. Three excellent companion plants with complementary shapes, textures, and colors, as well as similar growth requirements, are the desert marigold (Baileya multiradiata), orange caltrop (Kallstroemia grandiflora), and the desert bahia (Bahia absinthifolia). All three prefer full sun and thrive in dry, desert-type environments.
The desert marigold will produce mounds of striking yellow blooms from April to October. It flowers more consistently with deadheading. It is found throughout the Southwest from California to Texas and grows to heights of 1 to 2 feet tall. The plant has a branching growth habit with a single 1 1/2- to 2-inch flower at the terminus of each of its nearly leafless flower stalks.
Orange caltrop has grayish-green compound leaves and bowl-shaped flowers that superficially resemble poppies. In its native habitat, this wildflower grows along roadsides and on open plains, mesas, and desert slopes. During years of favorable growing conditions, it sometimes appears in masses across areas of southern Arizona. The showy flowers are about an inch wide, with five bright orange petals, deep orange stamens, and a crimson center. Seed for this wildflower, which also is called summer poppy or Arizona poppy, may be found through native plant outlets and at specialty nurseries. Rake seeds into the ground in June or early July and cover lightly with a mixture of soil and fine gravel, then wait for rain or water-in. Orange caltrop has a sprawling growth pattern, reaching a width of 2 to 3 feet and a height of 1 foot. It flowers between July and October.
Desert bahia, which also is known as hairyseed bahia or desert daisy, has silvery, 3-lobed foliage and yellow daisy-like flowers from spring to fall. It grows about a foot high and reseeds freely. It also spreads by rhizomes.
In the low desert it blooms almost continually and will need to be pruned back to the ground in late fall to encourage new growth in the spring. Desert bahia occurs naturally on rocky slopes and mesas in Arizona, New Mexico, Texas, and parts of northern Mexico.