Goethe's name for The Ultimate plant. All other plants are a mere shadow of the dawn-plant, the ideal in plantness. He came up with this while working on a taxonomy for plants. (He did some other, more lasting, stuff too -- he came up the word Morphology).
"The primordial plant would be the most wonderful creation of the world, for which nature itself should envy me. With this model and the key that it contains, one could invent an infinite number of plants, ones that despite their imaginary existence could possibly be real, thus which are not solely literary and painterly shadows and illusions, but which possess an inner truth and necessity. This same principle would be applicable to every other aspect of life as well."
-- Johann Wolfgang von Goethe, Italienische Reise in a letter to Herder on the 17th May, 1787.
The Urpflanze is the universal (almost one of Plato's forms) of 'plant'.