Hvorvidt om kilden er sand, kan jeg ikke udtale mig om.
"Generally calea is a southern plant. Growing Calea from seeds is a difficult task, However cloning this plant is extremely simple. the most common way to grow it is propagation from cuttings or layers, the latter of which is very easy in late summer. The Calea plant likes full sun, well drained soils, and medium irrigation. Anecdotal evidence suggests the flowering or post flowering plant harvested in the dry or cold season yields the best herbal product. A good soil mix for calea cultivation is: 1/3 of a rich substrate, 1/3 vermiculite and 1/3 of humus. or a light garden soil.
Propagation from seeds can be tried with the following method: Sow the seeds in a pot with the soil mix indicated as above. Don't cover the seeds, moisten the seeds with water and cover with a plastic bag. This little greenhouse needs from 4 to 6 hours of light to germinate. If the seeds dry out during this period, the plants will not germinate."
http://en.wikipedia.org/wiki/Calea_zacatechichi