I read elsewhere that people would plant honeysuckle around a privy to make it smell nice, or hollyhocks to help hide it.
After the great Loma Prieta earthquake in 1989, the Cypress Structure of the Nimitz Freeway (I-80, East SF Bay, Oakland, CA) had to be demolished and rerouted. Along with the reconstruction plans there was an obligatory archaeological study of West Oakland and the houses that would be affected by the construction. This study included an in-depth look at material culture of California in the late 19th - early 20th century (Oakland was founded in 1852) and many, many artifacts were found where outhouses had been located, since they were used as trash heaps.
I remember honeysuckle. I had an archeologist acquaintance who specialized in 17TH and 18th century and she spent most of her time in old privies. I found a certain satisfaction it that.