Some well-known Dioecious Plants include holly, asparagus, dates, mulberry, ginkgo, persmimmons, currant bushes, juniper bushes, sago, and spinach.
Some fruit trees also require a nearby tree of the opposite sex for fruit to be produced. The tree that ultimately bears fruit will be the female one.
With some trees, such as date trees, it isn’t apparent whether a tree is masculine or feminine until the tree is about three years old. Male flowers usually have small or no stigmas in them; female ones will be missing stamens.
You don’t need 1 male per 1 female; generally 1 male will serve to pollinate a number of female plants (exact range varies by type of plant.) 1 male date palm, for instance, can serve for 40 to 50 females. Sometimes, a branch from the opposite sex, say, a male branch, is even grafted onto a tree to ensure that male flowers are right nearby to ensure proper pollination. This is done with date trees.
You can also use this knowledge if you want a plant that doesn’t produce fruit — say if you want a mulberry bush that doesn’t produce messy berries all over the ground, you can choose a male mulberry plant.
Arabs would often just plant a few males to fertilize a grove of female date palms. In war raids on each other, they’d often slash down each other’s male date palms (presumably they knew how to figure out which ones were the males.) This was a good as cutting down all the female ones, and a lot less work, because without the male ones for pollination the female ones were useless.
“Dioecious” comes from two Greek words, “di” meaning “two”, and “oikos”, meaning “house.”