Philodendron X evansii is a hybrid between the arborescent Philodendron selloum and the climbing P. speciosum. (The hybrid name is a horticultural term and not a valid botanical designation.) Evansii is similar in habit to Philodendron selloum, but the leaf blades are not as deeply lobed and grow much larger than the leaves of either parent. The leaf blades of the photographed evansii were approximately 60 centimeters (24 inches) by 90 centimeters (36 inches).

Plants in the Araceae (Aroid or Arum family) have small flowers densely crowded along the erect inflorescence or spadix. The subtending sheath or spathe is a modified leaf. The flowers of most aroids emit strong odors to attract pollinators generally beetles or flies. (Note the yellow exudate on the surface of the spathe. No odor was noted at the time.)

All flowers produce heat, but the metabolic rates are slow and the heat is dissipated as it is produced. Aroid flowers are thermogenic producing heat as a result of the rapid metabolism of starch. Philodendron selloum flowers warm in the evening generating the highest temperature recorded in the family, 46° C (114° F). This parent of evansii is believed unique because it not only utilizes starches, but also oxidizes lipids (oils and fats).

The evansii inflorescence was photographed in the late morning in early April. The following day, the inflorescence was 'spent'; the spadix and spathe were wilted.

Phyllis M. Pineda of Colorado State University has an excellent article, "The Role of Odoriferous Chemical Compounds and Thermogenesis in the Pollination Ecology of Certain Plant Species". To learn more about the ecology of aroids and their pollinators, click on the link:

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