“Basils 2025” – Fourth Report: How can you easily distinguish between different species of Basil?

Foreword

How to distinguish the various main species of Ocimum at first glance… or at first sniff? 

How can Ocimum bisabolenum and Ocimum americanum be distinguished specifically by the morphology of their flower stems?

Photographs of Leaves and Fruiting Calyxes of the various main species of Ocimum

Ocimum bisabolenum

Ocimum kilimandscharicum

Ocimum americanum var. pilosum

Ocimum americanum var. americanum

Ocimum basilicum

Ocimum tenuiflorum

Ocimum campechianum

Ocimum gratissimum

Ocimum carnosum/selloi

Besobila from Ethiopia. “Ocimum bisabolenum” with a few Grains of Pollen competing on the pistil

Foreword

That being said, and presented photographically, below, any human being who genuinely cultivates an intimate connection with species of Basil, of the genus Ocimum, will recognize them “at first sight” – that is, at the mutual rebirth of this connection.

Thus, all the main species of Ocimum, presented below, can be recognized “at first glance,” with the occasional exception of certain ecotypes of Ocimum americanum var. pilosum… which can, nevertheless, be recognized “at first touch” – that is, at the first whiff of Citral when their leaves, or flower tops, are gently touched.

In fact, if I may digress into somewhat philosophical considerations, Basil species are like the Peoples of the Earth. The Ocimum genus is an “Archetype,” but it is not manifested in physical reality: it only has an informational (genetic) reality.

It is the diverse species of the genus Ocimum – Ocimum basilicum, Ocimum bisabolenum, Ocimum kilimandscharicum, Ocimum tenuiflorum, Ocimum gratissimum, etc. etc – that constitute the manifestations, the “Chlorophyll sub-Archetypes,” in the physical reality, of this Ocimum Archetype. Furthermore, these species, as physical manifestations of the Ocimum Archetype, originate from a specific Biotope: they are, literally, shaped by their environment.

The same applies to the Peoples of the Earth. Humanity (with a capital H) does not exist: it is merely an inept concept born of a nebulous ideology that seeks to globalize human beings into a universal melting pot. Hence the existence, for example, of the UN, the Organization for Universal Leveling – sometimes in “Gaza” mode… but not always.

It is the Anthropos that exists, as an informational and genetic Archetype. And it is the Peoples, the Ethnos, the Tribes, of the Earth, that are the physical manifestations – the “sub-Archetypes in Flesh and Blood” – of this Anthropos. Just like the various species of Basils, the various Peoples, Ethnos, and Tribes of the Earth originate from a specific Biotope: they are, literally, shaped by their environment.

How to distinguish the various main species of Ocimum at first glance… or at first sniff?

How can you distinguish between the various main species of Ocimum at first glance? First and foremost, by the color of the pollen on their mature stamens, as well as the color of the anthers. Next, by the color of the flowers, the overall appearance of the plant, and the shape of the leaves, bracts, and calyxes.

White pollen grains – approximately 50 microns in diameter – on an insect visiting an Ocimum basilicum flower

Ocimum bisabolenum. Secondly, this species is easily characterized by the mauve color of its entire flower, its very low and highly structured habit, and its very intense fragrance of myrrh, vanilla, and tutti-frutti.

Flower of Ocimum bisabolenum with Anthers and Pollen of orange/brick red color
Orange/brick red pollen ball on a bee foraging on Ocimum bisabolenum

Ocimum kilimandscharicum. Secondly, this species is easily characterized by the white color of its flowers, its long stamens, its very unstructured habit – and, for most ecotypes distributed in the Western world, by a chemotype strongly predominant in Camphor. 

Flower Ocimum kilimandscharicum with Anthers and Pollen of orange/brick red color
Pollen grain, orange/brick red in color, captured by the pistil of a flower of Ocimum kilimandscharicum

Ocimum tenuiflorum. Secondly, this species is easily characterized by the pinkish-purple color and the long peduncle of its flowers, by its very loose habit and by the very crinkled shape of its leaves.

Flowers of Ocimum tenuiflorum with Anthers and Pollen of yellow color. Ecotype “Green Tulsi from Thaïland”

Ocimum gratissimum. Secondly, this species is easily characterized by the green-yellow-brown color of its flowers, by its very broad leaves, and by its very tall, upright plants.

Flowers of Ocimum gratissimum with Anthers and Pollen of yellow color. Ecotype “Mtulé”
Flowers of Ocimum gratissimum with Anthers and Pollen of yellow color. Ecotype “Mtulé”

Ocimum basilicum. Specifically, some cultivars, but not all, are easily characterized by the crinkled and ruffled shape of their leaves. (“Mammoth”, “Napoletano” et “Laitue”); by the very purple color of their leaves (“Purple Rubin”, “Osmin”, “Rosie”, “Purple Ruffles”, etc); by the globular shape of their plants (“Grec”, “Floral White Spires”); by very small leaves (“Grec”, “Latino”); by floral clusters with very dense cymes (“Cardinal”, “Magical Michael”).

White Pollen of Ocimum basilicum – cultivar “Obsession”

Ocimum americanum. Specifically, some cultivars, but not all, are easily characterized by the small size of their flowers in Ocimum americanum var. americanum; by a chemotype predominantly containing Citral in Ocimum americanum var. pilosum; by a chemotype predominantly containing Camphor in Ocimum americanum var. americanum.

White Pollen of Ocimum americanum var. pilosum – ecotype “Esfahan” from Iran (USDA PI 253157). 

Ocimum carnosum/selloi. Secondly, this species is easily characterized by the shape of its flowers – in particular, the calyx – by the shape of its leaves, by the brown color of its anthers… and by its overall appearance.

White Pollen of Ocimum carnosum/selloi

Ocimum campechianum. Secondly, this species is easily characterized by the difficulty of seeing its tiny flower in the center of the calyx, by the reddish color of its anthers, by the shape of its leaves, by the shape of its calyxes… and by its overall appearance.

White pollen on the pistil of Ocimum campechianum
White pollen on the pistil of Ocimum campechianum

How can Ocimum bisabolenum and Ocimum americanum be distinguished specifically by the morphology of their flower stems?

Caveat. The purpose of this section is to highlight, based on the morphology of their respective flower stems, that there is no possibility of asserting, as some botanists still do, that the temperate Tulsi, the Ethiopian Besobila – which I have named Ocimum bisabolenum – could be Ocimum americanum… and even less so Ocimum americanum var. pilosum.

Pollen balls (and grains on the wings) from Ocimum bisabolenum

For example, the pollen grains of of Ocimum bisabolenum are 40% octacolpate, 30% heptacolpate, and 30% hexacolpate. In contrast, those of Ocimum americanum are 87% hexacolpate.

Views of the Calyx from below. Center: Ocimum bisabolenum. Left: Ocimum americanum var. americanum. Right: Ocimum americanum var. pilosum. The calyx of Ocimum bisabolenum is clearly distinct, with, among other things, a more elongated shape.
Above: Ocimum americanum var. pilosum. Below: Ocimum bisabolenum. The shape of the calyxes is different, as is the way they surround the unopened corolla.
Seeds. Right: Ocimum bisabolenum. Center: Ocimum americanum var. pilosum. Left: Ocimum americanum var. americanum.
Ocimum americanum var. pilosum: the lower lip is hairless

For example, with regard to the hairiness of the calyx. In Ocimum bisabolenum, the upper lip (the calyx shield) is almost hairless on the outer surface, and the lower lip is densely hairy on the inner surface.

In Ocimum americanum var. pilosum, the upper lip (the calyx shield) is hairy on the outer surface and the lower lip is hairless on the inner surface.

Ocimum bisabolenum grows to an average height of 35 to 40 cm in the garden. However, it can easily reach 55 cm in width, especially since this species of Ocimum is very adept at occupying all the space available to it. In a well-watered pot, the plants can reach 50 cm in height but, above all, spread very generously downward.

The flower stems are, on average, 10 to 12 cm long and can reach up to 18 cm. As for the dry calyxes, the largest are about 4 mm wide.

Dry calyxes, 4 mm in width, in Ocimum bisabolenum

The interval between the “cymes” (6 flowers simulating a whorl around the stem) is very small. Thus, there are 21 cymes on an 18 cm floral stem – i.e. with an average interval of 8.5 mm.

Center: Ocimum bisabolenum. Left: Ocimum americanum var. pilosum. Right: Ocimum americanum var. americanum.

Ocimum americanum var. pilosum – namely the different ecotypes that I have grown this year – are, on average, approximately 50 to 85 cm tall in the garden.

The flower stems are, on average, 20 to 30 cm long in “Sweet Dani” and 17 to 30 cm long in “Esfahan. PI 253157.” As for the dry calyxes, the largest are approximately 5.5 mm wide.

Ocimum americanum var. pilosum – ecotype “Esfahan” from Iran (USDA PI 253157). 

The interval between the “cymes” (6 flowers simulating a whorl around the stem) is relatively large. In Lemon-type Basil, the interval between cymes depends on the variety and ecotype: it varies from 16 mm to 19 mm.

Ocimum basilicum

Ocimum americanum var. americanum – namely the different ecotypes that I have grown this year and in 2022 – are approximately 35 to 55 cm tall in the garden.

The flower stems are, on average, 18 to 20 cm long in “Malawi Camphor” and other Zambian ecotypes. As for the dry calyxes, the largest are about 3.5 mm wide- and are therefore smaller than those of Ocimum bisabolenum. 

Ocimum americanum var. americanum. Ecotype “Malawi Camphor”

The interval between the “cymes” (6 flowers simulating a whorl around the stem) is very small. Thus, there are up to 35 cymes on a 21 cm floral stem in Zambian Camphor basil – with an average interval of 6 mm.

Photographs of Leaves and Fruiting Calyxes of the various main species of Ocimum

Ocimum bisabolenum

Freshly opened flowers – and top view of the Calyx
0.5 g to 0.6 g for 1000 seeds
Side view of the Calix

Ocimum kilimandsharicum

Very long stamens with orange pollen

Ocimum americanum var . pilosum

“Sweet Dani”
“Mrs Burns”
“Sweet Dani”. 1.4 g to 2.1 g for 1000 seeds in Ocimum americanum var. pilosum.
Side view of the Calyx. “Sweet Dani”

Ocimum americanum var. americanum

Dry Calices in an ecotype with Camphor from Zambia
“Malawi Camphor”. 0.55 to 0.75 g for 1000 seeds in Ocimum americanum var. americanum
Lateral view of the Calyx. “Malawi Camphor”

Ocimum basilicum

“Licorice”. 1.4 g to 2.4 g for 1000 seeds in Ocimum basilicum.
“Cardinal”
“Devotion”. 1.4 g to 2.4 g for 1000 seeds in Ocimum basilicum.
“Aromatto”
“Obsession”
“Réglisse”
“Osmin”
“Siam Queen”

Ocimum tenuiflorum

Ecotype “Krishna”
Ecotype from Gujarat in India
Ecotype “Krishna”

Ocimum campechianum

Calyxes
Calyxes seen from above

Ocimum gratissimum

Ocimum carnosum/selloi

Calyxes seen from above