This word is driving me crazy
'Macerado' is the Spanish word used in that context and with people with the same interests as me. I've looked it up at the RAE, the second entry will be the one I want to translate:
http://lema.rae.es/drae/?val=macerado
2. tr. Mantener sumergida alguna sustancia sólida en un líquido a la temperatura ambiente, con el fin de ablandarla o de
extraer de ella las partes solubles.
That is what I'm doing with pot marigold, although I can do it with other herbs, such as rosemary, with several plants or just one. I'm extracting the beneficial parts of a plant when steeping (?) them in oil.
So, for instance I could say: Oil in which pot marigold and rosemary (just to use the plural) have been steeped in
Would it be understood?
