Annuals Add Color to the Native Garden
Annual plants sprout from a seed, grow and die in the same growing season. Red-whisker clammyweed (Polanisia dodecandra) is a native annual that blooms for two to three months in late summer.
By Scott Woodbury
[This article was originally published in The Gateway Gardener March 2018 issue.]
Annual plants sprout from a seed, grow and die in the same growing season. Red-whisker clammyweed (Polanisia dodecandra) is a native annual that blooms for two to three months in late summer. It has rose pink to white flower petals and red stamens that are longer than the petals and look like red whiskers. The flowers are hummingbird moth and skipper magnets. Plants grow 18 to 24 inches tall and fit in tiny gardens. It is also one of those species of native plants that grows in the most inhospitable of habitats, gravel bars, and so grow well in most gardens. If you haven’t walked down to the gravel bar at Shaw Nature Reserve (or any gravel/sand bar along a river) you are missing out on one of life’s small but wonderful experiences. This is where shining bluestar, switchgrass and sandbar willow also grow and where fog settles in the early morning during spring and fall. It’s a magical place that deserves more attention.
Palafox (Palafoxia callosa) looks like pink baby’s breath. Snow-on-the mountain (Euphorbia marginata) has stunning white and green floral bracts. Blue waxweed (Cuphaea viscosissima) has tiny magenta flowers and purple fall color. Each of these late summer to fall blooming annuals tolerate dry or rocky soils though they also grow well in most sunny gardens. They look great in flower with fruiting beautyberry (Callicarpa americana), aromatic aster (Aster oblongifolius), native grasses and long-blooming star coreopsis (Coreopsis pubescens).
I think of some perennials as performing more like annuals for various reasons. Rose verbena (Glandularia canadensis) is perennial when growing in the wild but is gone in a few years in most gardens. Same is true of cardinal flower (Lobelia cardinalis) so we replant them every few years like we do with annuals. Blazing stars (Liatris spp.) are by no stretch of the imagination annual, but we replant them every year or two because they get eaten by voles constantly. Black-eyed Susan (Rudbeckia hirta) is a short-lived perennial or biennial (lives two years) in most landscapes but sometimes grows and dies in the same season like an annual. We will be planting many of them this spring to add more color for visitors and nectar for pollinators. In nature they are typically yellow but occasionally red and yellow. Shaw Nature Reserve will be giving away seedlings of both varieties at the Spring Wildflower Market on May 12, 2018 in celebration of the 25th anniversary of the Whitmire Wildflower Garden.
In early spring, swallowtail butterflies emerge from winter hibernation looking for nectar sources like western wallflower (Erysimum capitatum), an annual that grows wild on rocky glades. In gardens it prefers average to dry soils but is easy to grow. Like all of the annuals mentioned above, this one will spread slightly in the garden from seed.
There is a trick to having success with annuals. It’s easy to purchase and replace new plants every year but trickier to keep them going season after season. If you mulch in February and March, you may smother seedlings that try to come up in April, especially if you mulch too deeply (half inch or more) and thoroughly. But if you wait until April to mulch, you may get a crop of unwanted weeds. I’ve found that it’s better to spread mulch 2 inches deep where you don’t want annuals, but thinner or not at all in areas where you do want them. Ground leaf mulch is best because it is loose and porous. Targeted mulch-spreading in February and March gives you some control, however seedlings have a way of coming up where they want whatever you do. This gives the garden a more naturalistic look. Another way to encourage germination is to sow seeds on loosened bare soil in fall and mark with a tag, keeping mulch and leaves off of these areas. In April seedlings will emerge and you can either leave them be, thin them if too dense or transplant to other parts of the garden.
Blue-eyed Mary (Collinsia verna) is a shade-loving winter annual that breaks the rules of horticulture. It germinates in November, grows all winter and then blooms in spring. Like other annuals they suffer with more than a half inch of mulch. They prefer bare ground. In the wild they rely on flood waters to carry leaf litter away in fall or winter. Without it, seedlings can’t push through the layer of leaves. In gardens, rake leaves away immediately when they fall in November where you want a patch. Seedlings will germinate and thrive, even when it freezes. Winter seedlings are tiny and green with purple speckles. Blue-eyed Mary blooms in April with another woodland annual called Miami mist (Phacelia purshii), and perennials Virginia bluebells (Mertensia virginica), celandine poppy (Stylophorum diphyllum) and wild geranium (Geranium maculatum).
If you are wanting more color in your garden to enjoy and more nectar for wildlife, native annuals are the way to go, especially if you are gardening in containers. Keeping them going from year to year is not rocket science and can add enjoyment to your spring routine. You will have difficulty finding native annuals in garden centers but fortunately we will be selling them at the Shaw Wildflower Market in May. Until we see you then, happy gardening!
Horticulturist Scott Woodbury is the Curator of the Whitmire Wildflower Garden at Shaw Nature Reserve in Gray Summit, MO, where he has worked with native plant propagation, design, and education for 25 years. He also is an advisor to the Missouri Prairie Foundation’s Grow Native! program. Find suppliers of berry-producing native plants at www.grownative.org, Resource Guide.