Tuesday, May 25, 2021

Native Annuals revisited

The ubiquitous black-eyed Susan, Rubeckia hirta,
can bloom in its first season from seed
but may persist for up to 3 years.

A little over 10 years ago I kicked off this blog with an introduction to the idea of using native annuals in the home landscape.  I thought it was time to revisit this theme and add a little more detail with a focus on native annuals and biennials that can be used in the Mid-Atlantic garden.

While there is a growing interest in native trees, shrubs and herbaceous perennials there are very few native annuals promoted for landscape use in native landscape designs.  This lack of focus is due in large part because the longer-lived species can be counted on year after year to uphold the integrity of the design.  When included in a design, conventional annuals are often used as temporary accent pieces, just to add interest or fill a gap in the permanent landscape. 

In general, many of the annuals used in designed landscapes and home gardening are of exotic origin and have been further improved horticulturally for maximum visual affect.  These plants and methods are not bad or evil; they are just a several steps away from what would be considered natural to a given area.  While beautiful, these plants lack local character, certainly on a regional, if not continental scale.  To the extent that they are different from the local flora, they may not provide the same ecological value, such as food and shelter for wildlife in the area, as native species do. 

In contrast, native annuals may function more as perennials.  Those that are adapted to the local environment will die back after a season or two, but they will maintain a presence in the garden, by reseeding, though not necessarily in the same location.   For some people, this may be a problem since the plants will move around, disrupting the design.  Others would consider this as a natural phenomenon and appreciate how plants are able to find their proper niche.  The ideal native annual could be considered as a plant that develops quickly with more flowers, a longer flowering cycle than perennials, and that reseeds but is not invasive.

Plant Selection for the Mid-Atlantic

To generate my initial list of Mid-Atlantic annuals and biennials I used the USDA Plants database.  This database contains a listing of all plants identified as growing wild in the United States.  It does not, however, distinguish whether the plants in a location are indigenous or have escaped cultivation. Using the 'Advanced Search' function I first selected North American native species. Then I selected NJ, PA, MD, WV and VA as my Mid-Atlantic States.  For duration I selected annual and biennial and I selected 'forb' for plant type.  This resulted in a list of over 700 taxa.  This list of plant names included some duplication since varieties and sub-species are listed in addition to the species.  This database has since been revised but you can get similar results for your region using its new “Characteristics Search” feature.  Alternatively you can use the Wildflower Center’s combination plant search function on their database, but there you would be doing one state at a time.

Here are three short-lived Mid-Atlantic natives,
spotted beebalm over growing a patch of
American pennyroyal and
 backed up with black-eyed Susans.

Next, I scanned the list for species that I was familiar with that, in my opinion, had some garden value.  The attributes I considered included form, appearance of foliage or flower, scent of flower or foliage, or value to wildlife.  I came up with a list of over 40 species that I have or would like to have in my gardens.  These criteria are of course arbitrary in the sense that I am looking at features from a human perspective.  In reality each of these species has evolved to fill an ecological niche and, as such, has a real value in their natural home.  Most gardens, however, are created and curated by humans, and are not complete, natural ecosystems.  This is especially the case in urban and suburban settings where soils, water courses and wildlife corridors have been disrupted; although, we can aspire to create naturalistic areas where some semblance of a natural ecosystem can catch hold, particularly with the use of native plant species.

The Plants

Here’s a partial listing of the native annuals and biennials grouped according to their garden function.

Big Plants

Bearded beggarticks can grow from seed to about
5' tall in a season.  Bloom time is in late summer.
Despite their short life times some native annuals and particularly biennials can grow quite large, 4-6 feet tall.  These plants are best located in the background or in a larger format setting.

Bearded beggarticks (Bidens aristosa), American bellflower (Campanulastrum americanum), tall thistle (Cirsium altissimum), biennial gaura (Oenothera gaura, formerly Gaura biennis), jewelweed (Impatiens capensis), and evening primrose (Oenothera biennis).

Showy Plants

These species are of more manageable size and have good sized and/or showy flowers.

Climbing fumitory (Adlumia fungosa), partridge pea (Chamaecrista fasciculata and C. nictitans), plains coreopsis (Coreopsis tinctoria), Corydalis sempervirens, fleabanes (Erigeron annuus and E. philadelphicus), firewheel (Gaillardia pulchella), annual sunflower (Helianthus annus), cucmberleaf sunflower (Helianthus debilis), sneezeweed (Helenium amarum), standing cypress (Ipomosis rubra), spotted beebalm (Monarda punctata), sweet everlasting (Pseudognaphalium obtussifolium), black-eyed Susan (Rudbeckia hirta), clasping Venus looking glass (Triodanis perfoliata), and blue vervain (Verbena hastata).

Partridge pea returns reliably from seed
each year if open soil is available

Philadelphia fleabane is a prolific reseeder and
can grow anywhere there is an opening, such as a thin
 lawn.  Commonly grows as a biennial in my yard.


These plants will fill in space and while each has some interesting features, will not steal the show.

Hog peanut (Amphicarpaea bracteata), yellow corydalis (Corydalis flavula), American pennyroyal (Hedeoma pulegioides), Indian tobacco (Lobelia inflata), clearweed (Pilea pumila), red-whisker clammyweed (Polanisia dodecandra), Pennsylvania smartweed (Polygonum pensylvanicum), field pansy (Viola bicolor), and common blue violet (V. sororia).

American pennyroyal has very small flowers
but produces a strong minty scent when disturbed. 
Its tiny seeds can find their way into the smallest cracks.

Special Requirements.  

Most native annuals owe their long-term success to being adapted to some form of disturbance which makes it difficult for long-lived plants to get established.  Some species are adapted to very special conditions.  One common example is jewelweed (Impatens capensis).  This annual can grow quite large and sports distinctive orange flowers but it needs very wet soils to survive. 

Some interesting native annuals are hemiparasitic, their roots tap into nearby plants to help them develop fully.  Two examples are the False foxgloves, such as fernleaf false foxglove (Aureolaria pedicularia), which are parasitic on oaks, and Scarlet Indian paintbrush, (Castilleja coccinea), which grows with assistance from the roots of grasses. 

Winter annuals are a group of plants that have adapted their life cycles to avoid the heat and dryness of summer, or competition for sun light in a wooded setting, by doing most of their growth from fall into springtime, when light and moisture are more plentiful.

Spring blue-eyed Mary germinates in the fall and
blooms in early spring.  It is often found growing
under deciduous trees.

Some winter annuals found in the Mid-Atlantic include: Spring blue-eyed Mary, (Collinsia verna), Yellow fumewort (Corydalis flavula), Old field Toadflax (Nuttallanthus canadensis), Fernleaf phacelia (Phacelia bipinnatifida), Miami mist (Phacelia purshii), and Field pansy (Viola bicolor).

One trick with growing winter annuals is that you need to avoid pulling them out while you are cleaning up flower beds in the early spring. 

This clasping Venus looking glass came up on its
 own and bloomed in early June.  To encourage its
 return I avoided mowing the area so that it could
 set seed, but it will need open soil the following
 year so that it can grow.

A few of these species are commercially available as potted plants right now.  Others may be had by getting seed from native plant suppliers.  For others, these plants may occur naturally on your site and one just needs to be observant when they show up and then to take care that they are able to develop and set seed to create a new generation.