Posts Tagged ‘plant reproduction’

Lobelia cardinalis Cardinal Flower inflorescense

Cardinal Flower spike

In mid to late summer, the brilliant red blooms of the Cardinal Flower (Lobelia cardinalis) brighten areas with moist to wet soils in eastern North America as well as farther west to the southwestern states and California. The Cardinal Flower is an ideal example of a plant that has flowers adapted for a single type of pollinator, the hummingbird. The only hummingbird species in northeastern North America is the Ruby-throated Hummingbird (Archilochus colubris). This hummingbird gets its name from the iridescent red patch on the throat of the males—females lack the red patch. I’ve enjoyed watching these tiny, energetic birds darting about in a patch of Cardinal Flowers in my backyard, sipping nectar while performing valuable pollination services.

The show starts in mid summer

Cardinal Flowers extend their spike-like inflorescences upward beginning in mid summer and ultimately reach a height of 24” to 48” (60 to 122 cm). Individual flowers open in succession from the bottom of the stem to the top over a period of about six weeks. Each spike can have several to over 50 individual flowers. Each flower consists of a tube about 1 1/2” (3.8 cm) long that flares out into five petals—two outstretched petals forming an upper lip and three downward pointing petals forming a lower lip.

Cardinal Flower Lobelia cardinalis male phase

Cardinal Flower male phase

Lobelia cardinalis male phase beard

Close-up of male phase “beard”

Projecting upward from between the two upper petals of the tubular flower is another tubular structure that contains both the male and female reproductive parts. When the flowers first open, they’re in the male phase. In this phase, pollen is held in the tip of the tubular reproductive structure. A tuft of white hairs, looking like a tiny beard, extends beyond the tip. When the tuft of hairs is pushed back, the tip of the tube opens and releases pollen.

Lobelia cardinalis Cardinal Flower female phase

Cardinal Flower female phase

After about five days, the flower shifts to the female phase. In this phase, the female structure called a style elongates and extends out beyond the end of the tube. On the tip of the style are the stigmas, which are receptive to pollen from male phase flowers. At any given time, a spike can have unopened flowers, male phase flowers, female phase flowers, and remnants of flowers that have finished blooming.

Cardinal Flower Lobelia cardinalis male and female phase

Male and female phase flowers in bloom on same spike

Hummingbirds at your service

Hummingbirds are attracted to red flowers, and the Cardinal Flower certainly meets this requirement. Hummingbirds also have long, grooved, forked tongues that can lick nectar from the bases of long, tubular flowers like Cardinal Flowers. The hummingbird feeds while hovering at the flower’s opening, beating its wings at about 55 times per second.

Ruby-Throated Hummingbird Archilochus colubris w Cardinal Flower Lobelia cardinalis

Bright red flowers attract female Ruby-Throated Hummingbird

As the hummingbird hovers at the Cardinal Flower’s opening and enjoys a drink of sweet nectar, the top of its head comes in contact with the flower’s reproductive parts. If the flower is in the male phase, the hummingbird’s head will brush against the tuft of hairs at the end of the reproductive tube and receive a dusting of pollen.

Ruby-Throated Hummingbird Archilochus colubris w Lobelia cardinalis male phase

Hummingbird’s head is dusted with pollen from male phase flower
Copyright Edna Greig

If the flower is in the female phase, pollen already on the hummingbird’s head will stick to the female stigmas. Since male and female phase flowers are present at the same time, the hummingbird usually is successful in transferring pollen to female phase flowers. Cardinal Flower is self-compatible, so seeds will be produced whether the pollen is transferred to a female phase flower on the same plant or on a different plant.

Ruby-Throated Hummingbird Archilochus colubris w Lobelia cardinalis female phase

Female phase stigmas pick up pollen

But … beware an interloper

This mutually beneficial relationship between Cardinal Flowers and hummingbirds can be disrupted by an interloper. Learn more in the next Eye on Nature blog post.


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Epigaea repens or trailing arbutus

Trailing arbutus growing under pine

Trailing arbutus (Epigaea repens) is a ground-hugging evergreen shrub that has fragrant pink or white flowers in early spring. It’s also called mayflower, ground laurel, and gravel plant. It’s native to eastern North America and is a member of the acid-loving heath family, as is mountain laurel (Kalmia latifolia), blueberry (Vaccinium corymbosum), and wintergreen (Gaultheria procumbens). Unfortunately, trailing arbutus is not as common as it once was because in the past it was widely gathered to be sold in flower markets (see 1895 article in The Hartford Times).


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If you’ve walked in the woods in eastern North America, you may have come across Jack-in-the-pulpit (Arisaema triphyllum), a common and easily identified understory plant. It’s native to rich forests from Canada to the Gulf states. But this common plant has some not so common adaptations for reproduction.

Jack-in-the-pulpit flowers

Jack-in-the-pulpit blooms in April or May with an unusual flowering structure that gives it its name. The visible parts of the flowering structure are the club-like spadix (“Jack”) that rises within and above the edge of a leaf-like spathe (“the pulpit”). The upper part of the spathe curves forward and downward, acting as an umbrella to prevent water from flooding the 30 to 60 tiny flowers that are hidden at the base of the spadix. Individual plants have either male or female flowers—botanists call this dioecy.


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