Bauhinia and Hibiscus: A Comparison of Floral Reproduction

This posting is a response to the numerous hits made on a previous posting featuring the Non invasive Bauhinia tree. It seems that the interest lies in its reproductive nature. The purpose of this post is to improve the understanding of plant biology through comparative anatomy.

The title image shows the Bauhinia (blakeana ) on the left and the Florida native scarlet rosemallow (Hibiscus coccineus) on the right. I photographed the Bauhinia in the roadway median of our neighborhood. I photographed and display the scarlet rosemallow because it is such a stunning finding in the fresh water marshes of the Corkscrew Nature Preserve in SW Florida. It also shows that it is not a cultivar but it can self propagate without human intervention. Both plants are eye candy that must be appreciated in their out-of-door surroundings. In our community we have domesticated tropical hibiscus which are close relatives to the wild scarlet hibiscus

These two blossoming plants attract loads of attention. The Hong Kong orchid (Bauhinia blakeana ) and the cultivated tropical Hibiscus (Malvaceae) produce wonderful, flamboyant, visually attractive flowers. They are planted throughout our community. Additionally, these blooms have great staying power lasting for many months. Their flowering period stretches anywhere from eight to ten months, from September to June. They have, however, remarkably different reproductive powers. To reveal the secret of these two plants this posting compares the gross and micro anatomy of their two flowers.

A detailed diagram of a Bauhinia flower labeled with its anatomical parts, including bud, petal, sepal, stamen, pistil, ovary, style, and stigma, showcasing the flower's structure.
Bauhinia blossom with some pettals removed
Diagram labeling parts of a hibiscus flower including the stamen, ovary, style, stigma, petal, and sepal, accompanied by lush green leaves and a bud.
Hibiscus blossom with no petals removed

Gross and micro dissection reveals the major difference in the reproductive capacity of the these two perfect flowers. Dissection and microscopic examination of the ovaries shows that the hibiscus has ovaries while the bauhinia has no trace of ovules. It is unable to sexually reproduce.

Diagram illustrating the anatomy of a Bauhinia flower, highlighting its various parts including petal, sepal, stamen, anther, filament, ovary, style, stigma, and pistil. The text indicates that the flower is perfect but sterile, with no ovules or seeds.
This is a full dissection of the Bauhinia × blakeana blossom. Look at the top left images. You can see that under microscopic examination there are no ovaries within the ovary. This plant is infertile.

Anatomy diagram of a hibiscus flower, illustrating the components like the ovary, stigma, stamen, and petals, labeled with descriptions to explain its reproductive functions.
This is a full dissection of the Hibiscus blossom. Look at the top left images. You can see that under microscopic examination there are ovules within the ovary. This plant can produce seeds. It is fertile.

The five-petaled blossoms of Bauhinia plants are known as “perfect flowers,” because each individual bloom contains both female and male parts. Some varieties of the Bauhinia flower, such as the widely cultivated Hong Kong Orchid Tree (Bauhinia × blakeana), are known to be sterile. Bauhinia are monoecious, which means “single house”. This designation describes the dual sexual capacity in a single flower. The flowers can self pollinate or fertilize with pollen from another plant. The flowers attract pollinators such as hummingbirds, bees, butterflies, and more. Bauhinia × blakeana‘s sterility is due to its hybridization. Bauhinia blakeana is the result of conjugation of the very similar species Bauhinia purpurea ( Purple Camel’s Foot) and Bauhinia variegata ( Camel’s Foot Tree). Both of these are exotic species according to the Hong Kong Herbarium. The parent plants have partially overlapping flowering periods and geographical habitats, and the same range of bee and butterfly species as pollinators. Interbreeding Bauhinia purpurea and Bauhinia variegata is probable. The resulting triploidy of this plant has probably rendered this varietal sterile. The plants you see today are clones of the same flowers seen by Hongkongers more than a century ago. They are propagated asexually through cultivation of stem cuttings.

The Hibiscus is also considered a perfect flower which actually produces viable seeds. The hibiscus is a genus of flowering plants known for their large, showy flowers, belonging to the mallow family (Malvaceae). Fertilization of these plants is complex. Pollination may fail because of these five prerogatives.

  • Self-Pollination: Some hibiscus varieties are self-pollinating. This can make it difficult to cross-pollinate them.
  • Timing: Hibiscus flowers are only receptive to pollen for a short period, usually just a few hours.
  • Pollen Viability: Hibiscus pollen can lose its viability quickly.
  • Stigma Receptivity: The stigma needs to be receptive to pollen. The stigma, gateway to the ovarian, might not be receptive at the same time the pollen is viable.
  • Germination: Seeds take 12 to 24 months to bloom.

The hundreds of species of hibiscus are generated through human intervention of the pollination. Tropical hibiscus are propagated sexually from seeds or asexually from stem cuttings or plant division. In carefully controlled environments and with delicate, patient effort botinists have hybridized the tropical hibiscus to make hundreds of beautiful new varieties. The new plant varieties are propagated from cuttings or division to produced plants which are clones of their parents.

Illustration explaining hormonal fertility signals in plants during pollination, detailing four key hormones involved in the process.
In addition to timing, these four hormonal obstacles must be passed in the carpel for signaling a specific selection of pollen appropriate for germination of ovules in these species.

DISCUSSION of FINDINGS:

This is not a thorough scientific data collection. Three samples of blossoms from each of two trees were collected for a total sample size of six. All of the samples were made on the same day in April, 2020. There were no major local meteorological events for the year preceding this observation. There were no observations of the viability of the observed polled during this observation. Further study should be done to give this a high level of confidence of the conclusions.

SUMMARY:

In Florida the Bauhinia × blakeana and Hibiscus plants thrive and are found in almost all of the cultivated communities and household gardens. They are well tolerated but stable non-native species. Because of their reproductive limitations they are not invasive. We can feast our eyes on this banquet of form and color without fear of damaging the environment.

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#Bauhinia #Hibiscus #reproduction #flowers #invasives #anatomy #seeds #sterile #

Flowering Trees of SW Florida

We need a break form hurricane damage remediation. Some of these images and more were shown on previous postings. They are repeated here because many of these trees and flowers were damaged or lost during the hurricane Ian storm of 2022 and therefore are no longer available. We need a reminder of the past and promise of the future.

The freely available image is featured as the opener is copied from a Cindy Shuder-Sandine Facebook posting and attributed to a military reconnaissance photo. It shows hurricane Ian as it landfalls on Fort Myers beach 20 miles from where I live. It speaks a thousand words.

The flowers of the Bauhinia tree are stunningly beautiful with lavender petals and veiny traces of red made to attract the eyes of the beholder. The flower has male anthers full of pollen. In fact, in an ecstatic burst it releases its stamens full of thousands of pollen grains. The sensuous perfume attracts hummingbirds and bees. These hungry messengers dip into the sweet deep recesses of the flower and pick up the pollen and can carry it into the receptive flower of a female tree. In fact, it has its own female calix organelle within the same flower. It should be able to self-pollinate. But wait! The flowers bear no ova. It cannot reproduce sexually. It is baren. There will be no fertilized seeds. All that blossom is for enjoyment only. Most people who casually look at the gorgeous orchid like flower are unaware of the frustration of the tree which must propagate from cuttings at the whim of gardeners and lovers of the flowers. 

Hong Kong orchid tree (Bauhinia blakenia)

The flowering trees have many secrets from most people. Flowers of some trees may never be seen by seasonal residents. They may bloom during the hot and humid seasons. An example of this is the Flamboyant Royal Poinciana tree. It blooms in the summer when our population is much smaller than that of the tourist season. Of all flowering trees, it has the most breathtaking beauty of riotous red and orange blossom. 

Flamboyant Royal Poinciana, AKA Flame Tree
Flamboyant Royal Poincieana, yellow

Contrarily, some residents are unaware of the lack of some blooms during their absence. An example of this is the Golden Trumpet tree which shows its fertility in yellow colors for three weeks during spring break. The benefit of our climate is that it is tropical. The weather provides an opportunity to have a continuous parade of seasonal flowers in Florida. There is never a time when something is not blooming. 

Golden Trumpet (Tabebuia chryaotricha)
Pink Trumpet, (Yrebebuia heterophylia)

Through the years, resident and community efforts have enhanced our neighborhoods with many plants. The trees are the most outstanding because of their height and spread of their branches. They also hold that secret prize. In certain seasons they burst out with colors and shapes that are beyond wordy description. The images that were captured in these photographs are beautiful and pictures are indeed worth a thousand words. Beyond the visual impact they give us a breath of perfume and an earful of rustling music as their leaves clatter against one another. These images are just a sample of the dozens of flowering trees in our neighborhood of SWFL

Manolia

The flowering trees are appealing not only to us but also to a menagerie of animals from insects, reptiles, and birds. Most of all the flowers of the male plants are attractive to the female plants. The resulting reproductive products of fruits, nuts and seeds can be delicious as well as nutritious to a wide range of creatures.

Mexican Wild Olive (Cordia boissieri)

The colors of the flowers seem to be the most fascinating aspect of their appearance. The approximation of contrasting or complimentary hues and chromas is at times so obvious and sometimes so surprising. Sometimes it is shocking and other times it is soothing. There never seems to be an unpleasant combination. They seem to be more alive and sensuous than their cousins with less showy highlights like the oaks or even more so than the conifers.

Purple Glory AKA Princess flower,

It is such a treat to explore the streets, lanes, gardens, and wilderness to find something new or to see a variation of something familiar. Walking or bicycling provides an excellent opportunity to see and stop to appreciate the details and odors. It is a chance to see which other plants and animals are associated with the flowering trees. These cohabitations can be as intriguing as the flower. It can lead to an exploration of the details of environmental impact and an appreciation of ecological systems. I hope that you are inspired to go out and look for the trees and inspect them and perhaps appreciate their mysteries, of colors, shapes, timing, and scents.

Pink Shower (Cassia)
Dwarf Powderpuff (Calliandra haematocephala) attracting bees.

The flowering trees shown here originate from all over the world including Africa, South and Central America, China, and India and more. Untold secrets of these trees are yet to be discovered. What species of butterflies and moths are attracted to the various trees. Do the non-native trees interact or communicate with the native plant population? Are the plant defenses and pheromones compatible with the local insect population and microbial biota? There is still so much to discover. 

Pride of India (Lagerstroemia speciosa)
Coral Bean
Pink Shower (Cassia)
Plumeria, hot pink
Rose of Venezuela (Brown macrophyllia)
White Silk Floss (Celia speciosa)
Red Silk Floss (Ceiba speciosa)
African Tulip (Spathodea campanulate)
Cassia
Jacaranda (Jacaranda mimisifolia)
Malibar Chestnut AKA (Pachira aquatica) (Money Tree),
Scrambled Egg Tree (Glaucous Cassia)

The full list of the Flowering Trees of SW FL in found on Pages section of this site. It shows names, colors, sun exposure etc. They also can be geolocated on the Everglades Ark Epicollect data base site, There have been several other postings on this site showering the flowering trees during the special seasons .

#Scrambled Egg Tree #Glaucous Cassia #Malibar Chestnut #Pachira aquatica #Jacaranda #Jacaranda mimisifolia #Cassia #African Tulip #Spathodea campanulate #Red Silk Floss #Ceiba speciosa #White Silk Floss #Rose of Venezuela #Brown macrophyllia #Plumeria, hot pink #Pink Shower #Cassia #Coral Bean #Pride of India #Dwarf Powderpuff #Calliandra haematocephala #Pink Shower #Purple Glory AKA Princess flower #Lagerstroemia speciosa #Pink Shower #Golden Trumpet #Tabebuia chryaotricha #Magnolia #Golden Trumpet #Tabebuia chryaotricha #Flamboyant Royal Poincieana, yellow #Flamboyant Royal Poinciana # Flame Tree #Bauhinia blakenia #Hong Kong orchid tree

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Tree Blooming Near the End of Summer

With this season we are nearing the completion of the annual cycle of the flowering trees before departing to Africa and Europe. We started this series in the first week of December of 2021 with Trees of Christmas. It has been a remarkable adventure to learn about and collect images and data for the flowering trees in South West Florida (SWFL). Nearly every hue and chroma of the rainbow has been represented in the flowers ranging from deep indigo to brilliant intense reds. See more details about them on our Epicollect5 website. The trees all have exotic origins from Europe, Africa, India and Central/South America. Perhaps we will find some similar trees in Botswana’s Okavango delta and the plaines of Kenya. If all goes as planned we will be there in August of this year.

The featured image is a Purple Glory.

Many of the Blooming Trees of Late Spring are still in flower and in part include the Royal Poinciana, Jacaranda, Plumeria, and the Mexican Tulip. Missing is the Bauhania which had been blooming since Christmas. It has, at last, given up the last flowers.

Royal Flamboyant Poinciana. Still one of my favorite flowering trees, it is repeatedly throwing out new blossoms and filling the neighborhood with a spectacular display of color.

Here are the last of the newly blooming trees which I found on my last walk about.

Pride of India (Langerstroemia Speciiosa). Native to South Eastern Asia including India.
Australian umbrella (Scheffera actinophylla). An evergreen tree native to Queensland Australia. Toxic to dogs and cats when eaten or touched by the sap.
Not as big as a standard tree the Princess flower tree is also known as Purple glory. It has some of the most intense purple flowers.
Purple glory (Pleroma semidacandrum) is native to Brazil.

All of these blossoms are found less frequently as the summer progresses. The neighborhoods and wilderness are definitely less colorful. The remaining flowers will probably last for two months. We will look again after returning from the safari. The interesting plants now include palms and pines. Next year adventures will focus on the palm trees more closely showing the varieties of colors, leaf patterns and fruiting bodies. We will finish the series by making the autumnal blossoms posting during the end of October.

After returning from Africa I hope to post a number of articles comparing the landscape, water features, plants and animals to those in SWFL. I expect these to be very interesting and hope that you are also interested.

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#summer #trees #cycle #blossoms

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