The Mexican Primula

There are 21 Primula species listed for North America, and we usually think that means "in the USA and Canada". However there is one Primula which is found in Mexico. That species is Primula rusbyi. It is also found in the US states of Arizona and New Mexico. It is speculated that because it occurs in the Sierra Madre de Chiapas Mountains of Mexico, that it could also occur in the extension of those mountains into Guatemala. Occurrences from the Intermountain Region Herbarium Network show herbarium samples from the mountains of the Mexican states of Durango, Zacatecas, Coahuila and Chihuahua.

The species P. ellisiae was described from individual plants from the Sandia Mountains, New Mexico based on longer calyx lobes in relation to the tube and a larger sized seed capsule. These characteristics vary within populations and according to the Flora of North America “preliminary genetic analyses (S. Kelso and P. Beardsley, unpubl.) reveal no substantive genetic distinction between these individuals and those from elsewhere in the range”.  The name “Primula ellisiae” persists in cultivation but should be corrected to Primula rusbyi.


Calyx equals the tube

Calyx 2x's the tube

Primula rusbyi comes from mountain locations in dry areas but survives on moist slopes and cliff edges.

P. rusbyi in habitat

 See the Species Gallery for more images.

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Primula strumosa vs Primula sikkimensis

Being able to identify a species in the field is like being able to recognize a friend in a crowd. The more familiar you are with your friend’s features, the easier it is to find him. If you aren’t sure of a particular species, botanical keys can help you determine an identity, but that requires you to be familiar with some technical botanical terms.

When I was recently asked to distinguish between P. strumosa and P. sikkimensis, my answer included technical terms which not everyone was familiar with. Part of my reasons for starting the website “Primula World – A Visual Reference for the Genus Primula” at www.primulaworld.com was to be able to show the important characteristics of species and their variations through images.

Primula sikkimensis

Primula strumosa

Primula strumosa and Primula sikkimensis are both yellow flowered species found in a large area of the Himalaya including Nepal. They belong to different Sections (groupings) in the Genus, with P. sikkimensis being in Section Sikkimensis and P. strumosa being in Section Petiolares. Species in each Section are grouped according to common characteristics.

Though both of these species have yellow flowers, the structure of those flowers is different. P. sikkimensis has campanulate (bell shaped) flowers, and the calyx (the cup shaped structure at the base of the flower) is split to the middle into sharp triangular teeth (indicated by the red arrow). P. strumosa has flat faced flowers with a calyx split to the middle but into blunt (rounded) teeth (indicated by the red arrow).


Primula sikkimensis flowers

Primula strumosa flowers

 The leaves of these two species are also different. P. sikkimensis has leaves which are of a thin, papery texture and usually has a fairly distinct petiole (leaf stalk) whereas P. strumosa has leathery leaves with a broadly winged petiole (that is, no distinct leaf stalk).

Primula sikkimensis leaf

Primula strumosa leaf

Primula strumosa overwinters above ground as a resting bud. This resting bud is covered in yellow farina (a powdery substance) and the bud scales remain around the base of the plant, under the true leaves. Primula sikkimensis is deciduous and disappears completely below ground until Spring therefor it has no bud scales.

Primula strumosa resting bud

Most Primula species have seed capsules which split into 5 parts and empty from the top of the capsule. Members of Section Petiolares have a different capsule where a thin membrane covers the seeds which eventually disintegrates, releasing the seeds.

Primula sikkimensis seed capsule

Primula strumosa seed capsule

 

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