Mustard seeds also denote prosperity and money probably because they were a spice that could be traded. Mace and Nutmeg for similar reasons.
Ferns denote wealth that has been stored or acquired over a period of time.
Tulips also represent wealth because they were once a highly priced commodity.
Salt because it once worth the price of mineral ores.
The Oak is prosperity in the realm of authority.
The Money plant! (also known as the Jade plant). Feng Shui is what you need to look up as there are hundreds of plants and fruits associated with prosperity, including daffodils (buried gold) and holly is supposed to attract wealth.
The Horn of Plenty,sure you have seen pictures of it,at Thanksgiving time,and people make real ones,filling it with an assortment of fruit of all kinds,inside the basket that is called the horn of plenty. This basket represents prosperity.