Recognition of Winter Annuals – Part 1

Winter annuals have been appearing in gardens, lawns and landscapes for the past several months. These plants can be recognized through their characteristic shapes, and peculiarities, with a special focus on leaves since many will not bloom until spring.  The human brain has an incredible capacity for visual pattern recognition.  With practice and repetition, most of us can identify the common winter annuals from their earliest stages.  This is very helpful to gardeners and conservation managers, who want to eliminate undesirable weeds before they mature and multiply.

Occasionally, mistaken identities result in humorous plantings in public or private gardens.  In the municipal garden shown below, a small specimen of Senna obtusifolia – Sicklepod – was raised unknowingly as an ornamental shrub.  Watered and carefully tended by the garden staff, it reached huge proportions before someone explained the mistake.  The staff now fights large crops of young sicklepods that come up every spring all over that garden.

Senna obtusifolia
Sicklepod
Shrub

Here is a brief display of a few interesting  visual patterns seen in five winter annuals, and  one summer annual.   All of the plants are very common in the North Carolina Piedmont.  See if you recognize some of them.  The names are listed at the end.

Plant #1

Plant #2 (Perhaps the most difficult of the group)

Plant #3 (Actually blooming in the 2nd photo)

Plant #4

Plant #5

Plant #6 (The summer annual)

The identities of the plants are:

Plant #1 is Galium sherardia  –  Blue Field Madder

Plant #2 is Nuttallanthus canadensis  –  Blue Toadflax

Plant #3 is Scleranthus annuus – Knawel

Plant #4 is Erigeron annuus – Annual Fleabane

Plant #5 is Soliva sessilis – Burweed

Plant #6 is Lobelia inflata – Indian Tobacco

The Blue Toadflax plants seem more like young succulents and are often among the most difficult to identify.  More details about each plant will follow in the next article.

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Mulberry Weed (Fatoua villosa) – an Unwelcome Intruder

Mulberry Weed, Fatoua villosa, is an oddity – the only member of the Mulberry family (the Moraceae) in the Southeast that is a herbaceous plant rather than a shrub or a tree.  Originally from East Asia, it is a relatively new arrival in North America (early 1960s),and  is now spreading rapidly.  The common name is derived from the plant’s close resemblance to small, seedling Mulberry trees.

Mulberry Weed is a summer annual with an upright plant form and large, alternate leaves.  It is found primarily in disturbed areas, gardens and landscapes.  Below is an example of the plant form.

Fatoua villosa
Mulberry Weed
Plant Form

The leaves are triangular or sometimes slightly heart-shaped, with toothed margins and prominent veins.  The flowers are found in small clusters at the leaf axils, and have no petals.  Leaves and flowers are pictured below.

Fatoua villosa
Mulberry Weed
Leaf

 

Fatoua villosa
Mulberry Weed
Leaves

Young plants can also closely resemble False Nettle (Boehmeria cylindrica), and both can be  found in similar, shady habitats.  The leaves of False Nettle, pictured below, are opposite, rather than alternate – the best distinguishing feature.

Boehmeria cylindrica
False Nettle
Leaves

Mulberry Weed is a heavy seed producer, and the plants flower when only a few inches tall.  The seeds mature quickly, and the plants are known to produce 2 to 5 generations in a single year.  Thus the invasive potential is very high, and control is difficult once the plants are established.

For information on management and control, see this excellent bulletin from the NC State Extension Service:  https://content.ces.ncsu.edu/mulberryweed-fatoua-villosa

 

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A Frostweed (Verbesina virginica) Creates an Unusual Ice Bloom

From a distance it looked like a white plastic bag that had been snagged on the dead stem of a weed.  On closer inspection, it turned out to be a Frostweed (Verbesina virginica), with an ice sculpture wrapped around its stem.  Frostweeds earn their name in cold winters, when moist soil and a hard freeze combine to create the conditions for these plants to produce (passively) interesting and beautiful ice sculptures like the one pictured below.  For more detailed information on Frostweeds, see last years article : https://bwwellsassociation.wordpress.com/2016/01/27/frostweed-verbesina-virginica-blooms-in-central-north-carolina/.

The formation of Frostweed ice sculptures usually occurs at the base of  the plants.  In this case, the large stem was preserved structurally intact, and the ice was able to climb four feet up the six foot stem, an unusual happening.

Verbesina virginica
Frostweed

Below is a closer look at the ice pattern at the base of the plant.  An indistinct groove can be seen in the center, where the stem is located.

Verbesina virginica
Frostweed
Base of the  Stem

The two photos that follow illustrate the complex patterns formed when the cold sap turns to ice and either extrudes from or is formed at the surface of the stem.

Verbesina virginica
Frostweed
Closer View of Ice

Verbesina virginica
Frostweed
Close View of Ice

The picture below illustrates how the force of the expanding ice splits the stem open in the area near the top of the plant.

Verbesina virginica
Frostweed
Splitting Stem

Although the ice in these sculptures looks thick and robust, it is actually thin and fragile, adding very little to the weight of the plant.  This plant stayed upright during windy mornings in spite of the shell of ice, and hosted a number of large, repeat blooms.  The ice melts very quickly in sunny conditions.

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A Rare Winter Visitor – the Rufous Hummingbird

On a cold, windy morning in  December, in the North Carolina Piedmont, with the temperature holding at 24 F., a tiny hummingbird hovers over a nectar feeder.  Even at 24 degrees, the nectar in the feeder is not completely frozen, so the hummingbird settles on the feeder and begins to drink an icy morning breakfast of nectar slush.  This tiny visitor is a Rufous Hummingbird, a cold-hardy Western species that wanders in small numbers into North Carolina every winter.  In its normal range, it can nest as far north as southern Alaska, and overwinters in Mexico.  But the Rufous has a propensity for wandering far from its normal route, and isolated individuals can be found during winter all through the Southeastern United States, especially along the Gulf Coast.  In North Carolina, they tend to visit the Piedmont  rather than the coast, perhaps due to the larger number of nectar feeders available in the more populous areas.  The Rufous Hummingbirds visiting North Carolina tend to be juveniles or adult females.  Pictured below is an adult female Rufous Hummingbird, the bird described in the earlier narrative.

Adult Female Rufous Hummingbird

Adult Female Rufous Hummingbird

Rufous Hummingbirds are sometimes referred to by their Genus name: Selasphorus.  This is because the extremely rare Allen’s Hummingbird, also a Western species in the Genus Selasphorus, has been seen (3 records) in North Carolina.  The two are virtually indistinguishable except as adult males, so in an abundance of caution, females and juveniles of both species can be simply called Selasphorus Hummingbirds.  However, many observers are persuaded by mathematical probability, and stick with Rufous Hummingbird.

Below is the adult female Rufous Hummingbird showing the patch on the throat below the bill.  Depending on the light angles, the patch either appears black or an iridescent orange or red.  This, along with the rufous sides, helps to identify the species.

Adult Female Rufous Hummingbird

Survival of the Rufous Hummingbird is greatly enhanced by winter nectar feeders.  Maintaining a nectar feeder over the winter is surprisingly easy; in many respects, easier than in the summer.  The cold temperatures inhibit the ants and yellow jackets, and keep the sugar solution from spoiling.   The sugar in the water also delays freezing until temperatures are into the mid to high twenties F.

For more information about Rufous Hummingbirds, see  the  Birds of North Carolina website:  http://ncbirds.carolinabirdclub.org/view.php?species_id=352

and  about winter hummingbirds:  http://naturalsciences.org/research-collections/hummingbird/nc-hummers

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The Anglestem Primrose-willow, Ludwigia leptocarpa

The primrose-willows, which are sometimes called water-willows, are common and widespread along the lake shores, ponds, and wetlands of the Coastal Plain and Piedmont of North Carolina.   They are members of the Evening Primrose family, the Onagraceae, and are usually found as erect and well branched, small to medium sized shrubs.  One of the largest of these is Ludwigia leptocarpa, the Anglestem Primrose-willow.  Pictured below is a single plant of L. leptocarpa standing alone, followed by a group of plants forming a small hedge along the shore of a lake.

Ludwigia leptocarpa
Anglestem Primrose-willow
Shrub

Ludwigia leptocarpa
Anglestem Primrose-willow
Hedge of Shrubs

L. leptocarpa has noticeably elongated floral tubes, a distinctive characteristic that distinguishes it from all of its close relatives.  In fact, another common name for this plant is Longpod Primrose-willow.  The photo below shows the long floral tube of a flower bud, a flower, and a flower that has just lost its petals.  Notice the extreme pubescence seen on the stems and floral tubes, another characteristic which distinguishes it from its near relatives, whose stems are smooth.

Ludwigia leptocarpa
Anglestem Primrose-willow
Floral Tubes

As the flowers age, the floral tubes turn red, making them more visible from a distance.

Ludwigia leptocarpa
Anglestem Primrose-willow
Red Floral Tubes

The developing seedpods retain the distinctive elongation.

Ludwigia leptocarpa
Anglestem Primrose-willow
Seedpod

L. leptocarpa has a sharply angled stem which is the source of the  common name Anglestem Primrose-willow.  See below.  Notice also the  heavy pubescence.

Ludwigia leptocarpa
Anglestem Primrose-willow
Angled Stem

L. leptocarpa has flowers with 5 to 7 petals and sepals, while its closest relatives have 4- petaled flowers.

Ludwigia leptocarpa
Anglestem Primrose-willow
Flower

Ludwigia leptocarpa
Anglestem Primrose-willow
Flower

The bright yellow flowers of L. leptocarpa do somewhat resemble the flowers of Evening Primroses (Oenothera biennis), and are the source of part of the common name.  Their shrubby early growth and narrow, lanceolate leaves also resemble young willows.  Although most of the Ludwigia genus are herbaceous, Ludwigia alternifolia  (Seedbox) has woody stems, which resemble young willows even more.  Thus the shrubby members of the Ludwigia genus  came to be known collectively as Primrose-willows.

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A Brief Look At Gonolobus Anglepods and Matelea Spinypods

Seed pods can serve as a handy adjunct to identifying our two genera of North Carolina Milkvines, particularly in late summer and fall, when the vines are no longer in flower, and caterpillars have ravaged the foliage.  Often the only thing left in the fall is a lonely pod or two on a ragged vine.

Both Gonolobus and Matelea have seed pods so unique that they serve as their common names.  Gonolobus suberosus var. suberosus is called Eastern Anglepod and Matelea decipiens is called Deceptive Spinypod.

The Gonolobus anglepods have five sides, each separated by a distinct ridge.  The pods are asymmetrical with the sides being unequal – either narrow or wide.  See below.

Gonolobus suberosus var. suberosus
Eastern Anglepod

Below are unusual “twin” anglepods.    Notice that the ridges are minimal  on the anglepod on the left, giving it a smoother look.

Gonolobus subersosus var. suberosus
Twin Anglepods

These anglepods measured about four inches long and an inch or a little more wide.  Most had very pronounced angular ridges, as the one below.

Gonolobus suberosus var. suberosus
Anglepod

The spinypods of Matelea decipiens are covered with small knobs that eventually become prickly when the pod matures.  Below are a series of photographs depicting the growth and gradual maturation of Matelea spinypods.    In the first photo below, note that a few of the flower petals still remain on the swelling fruit.

Matelea decipiens
Very Young Spinypods

 

Matelea decipiens
Early Spinypod

 

Matelea decipiens
Spinypod

As the pods mature, they become increasingly elongated, often assuming a shape like a spindle.

Matelea decipiens
Spinypods

Matelea decipiens
Spinypod

The final photograph below shows the mature spinypod compared with the anglepod of Gonolobus.  The darker contrast background shows that the ends of the knobs have finally hardened into prickly spines.  This spinypod measured 5 and 1/2 inches long.

Gonolobus suberosus var. suberosus Anglepod, above
Matelea decipiens
Spinypod below

The spinypods of Matelea decipiens and Matelea carolinensis are virtually indistinguishable from  each other.    M. decipiens  was used due to the higher number of pods that happened to be available this year.

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Summer Briefs: Apios americana and Portulaca oleracea

Apios americana – Groundnut

Summer is the peak season for flowering vines in North Carolina.   Best known are the many species of brightly colored morning glories, and the beautiful passion flowers and butterfly peas.   Although it is quite common, Groundnut is one of the lesser known summer flowering vines.   It generally grows along the margins of rivers, streams and lakes, often draped over shrubby vegetation.  Its common name gives no hint of its flowers, and is based on the underground tubers the plant produces – tubers which are high in protein and nutrients, and were commonly eaten by Native Americans and early settlers.

Usually only the outside of the flowers, with their odd, pink shades of color, are visible.

Apios americana
Groundnut
Flowers

Approaching the flowers is often difficult due to their location near the water’s edge.   And the flowers themselves only open fully for a few hours a day.  But if all goes well, the unusual form and deep, rich colors of the open flower can be observed.

Apios americana
Groundnut
Flower Close Up

Groundnut is a member of the pea and bean family, the Fabaceae.  It differs from most of its relatives in having five to seven leaflets rather than three.  This makes distinguishing the vine from its relatives easy, even when the flowers are not present.  Below a leaf with five leaflets and the bean-like pod of the fruit can be seen.

Apios americana
Ground Nut
Pod and Leaflets

Portulaca oleracea– Common Purslane

Portulaca oleracea, which is the largest wild portulaca in North Carolina, is usually considered an exotic weed, but there is some evidence for nativity, at least in part of its range.  It is considered common and widespread in North Carolina, but is strangely absent from Wake and  surrounding counties on distribution maps.  The photos in this article, however, are from Wake County.    The succulent leaves are flat, smooth and glossy.  This portulaca can be found growing in gardens, disturbed soils, sandy soils, and, in this case, a stony water mitigation area.  The typical plant form is shown below.

Portulaca oleracea
Common Purslane
Plant Form

Portulaca oleracea is a very late summer annual that grows and blooms quickly.  Its yellow flowers only open in full sun, and sometimes don’t open completely even then, as seen below.  It is easy to identify when blooming, as it is the only portulaca in North Carolina that has flat leaves and yellow flowers.

Portulaca oleracea
Common Purslane
Flowers

Growth radiates from a central taproot; the stems do not root at the nodes.   The prostrate growth habit can create mats that form a large circle up to two feet across.  But in this case, the huge mat pictured below actually measured three and one-half feet across. It was the largest plant in the mitigation area.

Portulaca oleracea
Common Purslane
Plant Form

Although Portulaca oleracea is known to be drought resistant, the huge size of the plant pictured above did not serve it well.  Above average rainfall through late June and July aided rapid growth .  But the plant did not survive an extended period of extreme heat and drought in August.

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