“Basils 2025” – Third Report: Reproductive biology and interspecific crossings in Ocimum kilimandscharicum

Summary 

The species Ocimum kilimandscharicum is characterized by a predominant self-sterility… and, therefore, an almost obligatory cross-pollination

History of my 3 sterile Ocimum kilimandscharicum plants crossed with X – with orange pollen

History of my 4 sterile Ocimum kilimandscharicum plants crossed with X – without pollen

Ongoing discoveries involving another wave of Ocimum kilimandscharicum plants crossed with X

Flower of Kapura with anthers and pollen of orange color

The species Ocimum kilimandscharicum is characterized by a predominant self-sterility… and, therefore, an almost obligatory cross-pollination.

The first of my main discoveries, this summer of 2025, is that the species of Basil, Ocimum kilimandscharicum, is mostly self-sterile – and therefore under a regime of almost mandatory allogamy.

Indeed, this summer, in our garden, I just discovered that the first floral stems harvested from the unique Ocimum kilimandsharicum plant that germinated, accession PI 652052, from the GRIN/USDA (wrongly presented by their taxonomists as Ocimum americanum) bear almost no seeds – whereas this plant was growing under an insect-proof breeding tent… thus, free of insects.

Ocimum kilimandscharicum

This means that we have produced certified organic seeds of Ocimum kilimandscharicum – with Terre de Semences and the Kokopelli Association – since 1994 without ever being aware of its authentic reproduction system. The same applies to all our organic seed colleagues in Europe and, especially, in North America – for even longer.

We have followed, for about thirty years, the principle of self-fertility and non-interspecific hybridization, in the major species of Ocimum, and the principle of certain intraspecific hybridization, in Ocimum basilicum and Ocimum americanum. Wrongly, obviously, in the case of Ocimum kilimandscharicum!

Ocimum kilimandscharicum. PI 652052

I would like to clarify, again, that I introduced Ocimum kilimandscharicum – in the form of certified organic seeds – in France and Europe, in 1994, with the first catalog of Terre de Semences. Ocimum kilimandscharicum was part of our range of organic seeds – nearly 600 accessions. We have never found information on the floral and reproductive biology of this species. 

Moreover, a professional seed grower cultivating a hundred, or a few hundred, plants of Ocimum kilimandscharicum will not be able to discover the almost obligatory allogamy characterizing this species because it will predominantly manifest only in intra-specific allogamy in his field – namely, between plants of the same species.

On the other hand, in our gardens this year, it is an intra- and inter-specific allogamy, given the few Kapura plants (about twenty) cultivated among hundreds of other plants of various cultivars or ecotypes of the following species: Ocimum basilicum, Ocimum bisabolenum, Ocimum americanum, Ocimum tenuiflorum, Ocimum gratissimum, Ocimum carnosum, and Ocimum campechianum.

Last month, I incorrectly mentioned that there were no studies on the reproductive mechanisms of Ocimum kilimandsharicum. To validate my discovery regarding its almost self-sterility, I therefore set off again in search of information on the web… and I indeed found some in three studies:

1. A Nigerien study, from 2018, highlighted that the seed production in Ocimum kilimandscharicum is higher when the diversity of pollinating insects is abundant. At 50 meters from the forest, the diversity of insect species is three times greater than at 220 meters – and the number of insects is double. LINK

2. A study from Bangalore, in 2020, highlighted, in Ocimum kilimandscharicum, the lower amount of seeds in cage pollinations compared to open pollination gardens or pollination sites by the local bee Apis cerana. LINK

3. A Kenyan study, from 2023, highlighted that plants of Ocimum kilimandscharicum growing under veiled pollination cages – hence, in strict autogamy – produced 103 seeds while those growing in gardens, under open pollination, produced 22,960. LINK

In the foreground: “Elephant Head” Amaranthus cruentus. In the background: Ocimum kilimandscharicum flanked by two Ocimum gratissimum

Then, just after posting – and translating into English – my second report “Basil 2025”, I informed Peter Nick, the director of the Botanical Institute of Karlsruhe, of my discovery, who asked me if I thought there was a delay between the maturity of the stamens and that of the style in Ocimum kilimandscharicum.

It was then that I remembered my sequence of photos, taken in 2022, of the opening of an Ocimum kilimandscharicum flower. It is clearly visible there that the flower blooms with stamens completely devoid of pollen, while, as soon as it opens, an insect rushes to the bottom of the corolla to extract nectar – thus signaling the maturity of the female reproductive organ.

Here is a sequence of photographs (by Xochi) illustrating the delicate blooming of an Ocimum kilimandscharicum flower. In homage to Beauty!

I did not stop at this sequence of photographs and I went on to dissect a few floral buds ready to bloom in order to check that they were characterized by the same protogynous reproductive regime. And I took a few photographs of them.

Ocimum kilimandscharicum. The Pollen is not yet ripe
Ocimum kilimandscharicum. The Pollen is in the process of maturing

I even managed to capture the opening of flowers of my 3rd Ocimum kilimandscharicum hybrid (Kapura X. OR. 04/2025) – which emerged in the garden this summer 2025 – featuring orange-colored anthers and orange pollen. I was also able to observe the same phenomenon of orange-colored anthers (sometimes very light) but without pollen, at the beginning of anthesis.

One of the photographs highlights two anthers with ripe pollen while the other two anthers are still virgin.

Two anthers with ripe pollen while the other two anthers are still virgin.

In provisional conclusion, this almost total self-sterility in Ocimum kilimandsharicum explains even better, of course, the inclination of this species to be courted by the very numerous buzzing pollinator insects moving from one species of Ocimum to another.

History of my 3 sterile Ocimum kilimandscharicum plants crossed with X – with orange pollen

During the summer of 2024, two Basil plants appeared in my garden, spontaneously, with pollen and anthers of orange color – as characterized by Ocimum kilimandscharicum. However, they had very different leaves and a Cinnamon scent – namely, a predominant chemotype in Methyl cinnamate.

The first plant – which I named Kapura X. OR. 01/2024 (OR meaning Orange Pollen) – measured nearly 1 meter in amplitude by autumn 2024, after having emerged, spontaneously, in a path with very compact soil covered in olive bark. At the end of November, I tried to extract it but could only unearth a small part of its root system… and it did not survive the approach of winter.

This plant was very exceptional in that the majority of its branches bore purple flowers while a minority bore white ones – all with pollen and orange anthers.

In fact, the situation was a bit more complex in that the white flowers were borne by stems and calices of a purplish color that turned green at full maturity. As for the purple flowers, they were borne either by stems and calices of a purple color (staying purple); or by stems and calices of a purplish color that turned green at full maturity.

Kapura X. OR. 01/2024 with a somewhat purplish foliage
“Magic Mountain”

The second, later – which I named Kapura X. OR. 02/2024 – had less amplitude and grew in a pot because I was able to dig it up from the garden. It survived the winter on a wind-swept balcony, at temperatures of about -7° and, above all, during four days of very frosty fog. Its corolla is relatively white, with a slight purple tint. The pistil is purple but the stamens are white.

Flower of Kapura X. OR. 02/2024. The pollen is not ripe yet as the flower has just opened
Flower of Kapura X. OR. 02/2024. With ripe pollen on the anthers

The first Kapura X. OR. 01/2024 plant survived through a single cutting that we managed to save and transplant in January. I named it Kapura X. OR. 03/2024. Like its mother plant, it is huge but, unfortunately, at least for now, it has not retained the exceptional double coloring of the flowers. In fact, it only has white flowers carried by stems, and calyxes, that are purplish in color becoming green at full maturity. It is worth mentioning that its flower stems are very long, reaching 34 cm.

Kapura X. OR. 03/2024

During the summer of 2025, another hybrid Kapura appeared spontaneously in the melons. I unearthed it and repotted it in order to study its evolution. I named it Kapura X. OR. 04/2025.

Kapura X. OR. 04/2025. With pollen, and anthers, of orange color

It already has a strong amplitude. Its anthers and pollen are characterized by an orange color. However, unlike other Kapura with orange pollen, its floral tops are free of purple coloring and, therefore, anthocyanins.

At the start of anthesis, the stamens are devoid of pollen

Given the amplitude of the plants and the chemotype Cinnamon, I suspect that these are spontaneous crossings involving Ocimum kilimandscharicum and Ocimum basilicum. Why not involving Ocimum americanum? Because so far, there are only proven examples of crossings between Ocimum kilimandscharicum and Ocimum basilicum.

Indeed, this would not be the first case since the agronomic center of Lucknow, in India, has developed new cold-resistant lines from natural hybrids involving these two species, growing in their gardens around 2010. And this is without mentioning the introduction of sterile lines such as “Magic Mountain F1”, “Magic White F1” and “African Blue”.

According to the study, from Lucknow, in 2020, “Generation of novelties in the genus Ocimum as a result of natural hybridization: A morphological, genetical and chemical appraisal”, [45] the two hybrids presented have orange-colored pollen – but less bright than that Ocimum kilimandscharicum’s one.  

Source: “Generation of novelties in the genus Ocimum as a result of natural hybridization: A morphological, genetical and chemical appraisal”. 2020.

According to the authors: « These two novel Ocimum hybrids exhibited intermediate morphological features of two parental species. Inter simple sequence repeats (ISSR) analysis and DNA barcoding with the plastid non-coding trnH-psbA intergenic spacer region reafrmed unambiguous parental identifcation and dif- ferentiation of these natural hybrids from other available Ocimum species. Consequently, gas chromatography- mass spectrometry-based metabolite profling of two hybrids identifed them as specifc chemotypes with the presence of a unique blend of specialized metabolites from the parental species, which are either rich in terpenes or phenylpropanoids. Additionally, expression analysis of key genes from terpenoid and phenylpropanoid pathways corroborated with diferential metabolite accumulation. Thus, these two Ocimum hybrids represented the novel chemotypes, which could be useful in commercial cultivation to produce novel essential oil and bioactive constituents».

History of my 4 sterile Ocimum kilimandscharicum plants crossed with X – without pollen

I sowed, in the spring of 2025, seeds of Kapura, from my very diverse basil garden in 2022, as well as seeds from a plant that appeared spontaneously during the summer of 2024, along with seeds from the Kokopelli Association – produced in 2017 and that I had already cultivated during the summer of 2022.

I then kept about twenty Kapura seedlings to cultivate them in pots or in the garden. This resulted in a few crossbred plants that were deformed and weak; about ten normal plants; and four crossbred plants that grew beautifully on my balcony.

These four crossed abnormal plants appear less camphoraceous at first glance. Three of these plants are characterized by hyper-branching – two of which have very short branches: the main stems produce 12 to 24 floral sub-stems that are 6 to 10 cm long.

Hyper-ramification with Kapura X. SP. 04/2025. 
Hyper-ramification with Kapura X. SP. 03/2025. 
Hyper-ramification with Kapura X. SP. 03/2025

Furthermore, they have flowers with relatively short stamens and anthers that are white/gray/beige – and sometimes a very light orange – completely lacking pollen… instead of bright orange anthers, and bright orange pollen, and very long stamens.

During the summer, I noticed that these four plants are all sterile as well – namely, that their floral stems are perfectly developed but with fruiting calyces that remain empty.

These four crossed Kapuras plants are characterized, therefore, by a total absence of pollen, an abundance of nectar, and a total absence of seeds.

Are there ecotypes of Ocimum kilimandscharicum with white anthers and white pollen? The only mention of light-colored pollen for this species is found in the 2017 study, “Diversity of the genus Ocimum (Lamiaceae) through morpho-molecular (RAPD) and chemical (GC–MS) analysis”. Their authors assert that  «Ocimum kilimandscharicum has brick red or gray colored pollen which was entirely different from other genotypes.» LINK.

On the other hand, there is a study from 2015 titled “Ocimum kilimandscharicum Guerke (Lamiaceae): A New Distributional Record for Peninsular India with Focus on its Economic Potential”, which comments on the discovery of Ocimum kilimandscharicum plants in two sites of different agro-ecological zones of Odisha in India. LINK.

The photographs presented there highlight plants with somewhat different foliage and, above all, flowers with white anthers. In these photographs, the pollen is unfortunately not visible, but the authors mention the presence of seeds – and thus, of fertile plants.

Would there be, then, natural hybrids, but fertile, involving Ocimum kilimandscharicum in certain regions of India?

This spring, unfortunately, I did not keep track of all my Ocimum kilimandscharicum seedlings according to the various seed sources… because I did not imagine the nature of my discoveries regarding this species.

I suspect, however, that some hybridized plants of Ocimum kilimandscharicum may have resulted from a spontaneous crossing during the 2017 season, at Maryse’s place, who was a producer for Association Kokopelli, where she produced 337 grams of seeds as well as nearly a kilo of seeds from the Ocimum basilicum ecotype, “Mrihani” – which represents a substantial opportunity for crossings involving these two species due to the very large number of seed-bearing plants… and the irresistible attraction for pollinators from all spheres.

In conclusion, in terms of the integration of genes for resistance to Basil Downy Mildew, into edible Basil cultivars of Ocimum basilicum, the Ocimum kilimandscharicum X Ocimum basilicum pathway could prove fruitful. This is especially true if less “camphoraceous” ecotypes of Ocimum kilimandscharicum are available, as consumers are not fond of camphor on their plates. There are, in Africa, for example, other ecotypes of which are devoid of, or very low in, Camphor. Such is the case for the GRIN/USDA ecotype, PI 652052, which had for chemotype, in one analysis:  Estragol 31%, Camphor 12%, Eucalyptol 11%, Eugenol 9%.

In another conclusion, if Ocimum kilimandscharicum spontaneously crosses with Ocimum basilicum, and vice versa, it is quite possible that Ocimum kilimandscharicum could cross with other species of Ocimum – and vice versa.

Ongoing discoveries involving another wave of Ocimum kilimandscharicum plants crossed with X

I sowed, during the summer of 2025, another wave of seeds of Ocimum kilimandscharicum from the plants cultivated in the spring of 2025 (Kapura 2025), which originated from the unique mother plant (Kapura 2024) that appeared spontaneously during the summer of 2024.

Of the 30 seedlings that I replanted from the seed trays, I kept 20 which I transferred to larger pots with good potting soil. The results were very surprising in that 18 of the Kapuras are clearly crossbred with only 2 Kapuras that, at first glance, seemed authentic – but they are not. Indeed, their flowers do have orange pollen but they are small and light purple in color. This means that this sowing resulted in 100% crossbred plants.

I was so surprised by the extent of these crossings that I sowed, again, last week, trays (of 72 cells) of Ocimum kilimandscharicum seeds coming from Kapura 2024 and Kapura 2025.

Indeed, I am extremely intrigued by the phenotypic similarity of the crossed plants obtained in these seedlings. Indeed, the size of the leaves varies somewhat, as well as the color of the emerging floral buds, but the overall growth habit is very similar. It is as if the pollen, responsible for the spontaneous crosses, comes from the same donors.

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In the middle, an authentic Kapura surrounded by two crossed Kapuras with X – perhaps with a Cinnamon type.
Some flowers, which have just bloomed, are free of pollen with very pale orange anthers.
A grain of pollen was captured by the stigma of the pistil.

In my First Report, published on July 12, 2025, I had written: «This year, I am even going so far as to plant a “Cinnamon” or “Licorice” Basil together with an Ocimum kilimandscharicum in the same pot in order to play the lottery with the Archetype Ocimum! Why? Because it seems that my first two spontaneous crosses involved the chemotype “Methyl Cinnamate” in Ocimum basilicum.»

It would seem, therefore, a priori, that some of these crossed Kapuras could be with these Basils of the “Cinnamon” type – whose floral tops have purple coloration.

In a few weeks, I will know the nature of the seedlings from my last batch of Kapura 24 and Kapura 2025 sowing.

It therefore seems very easy for gardeners to obtain hybrid plants of Ocimum kilimandscharicum. In a garden, it is sufficient to cultivate a few of them completely isolated from each other – and surrounded by many other basils of Ocimum basilicum. Due to their self-sterility, the plants of Ocimum kilimandscharicum are then statistically much more pollinated by male pollen coming from the surrounding plants of Ocimum basilicum.