Houseplants are, in terms of human civilization, a fairly recent phenomenon. While small pockets of people from Ancient Egyptian, Greek, and Roman cultures were known to have a few houseplants as decor, only the richest could afford it. After these civilizations fell, indoor plants were mostly restricted to foods or spices. For over a thousand years, houseplants didn’t exist.
In the late-18th century, “flower tables” became a popular feature of the fashionable French salon. By then, naturalists had developed effective plant breeding; the bourgeois could now include fanciful arrangements of these crossbred and colorful flowers. Plant breeding also created hardier species that could survive the trauma of transplanting. Nurseries became a profitable business. While houseplants became slightly more common, they were still restricted to the wealthy, or near-wealthy.

Outdoor plants finally came indoors on a large scale in the late 19th and early 20th century, during the Victorian and Edwardian eras. City populations exploded with the Second Industrial Revolution, and smaller homes and apartments became common. Factories jobs carried a higher health risk, but they also produced a larger paycheck. Households now had a very unusual problem: how do they project their wealth and social superiority…in such a small space?
Some displayed wealth with fine clothes and fashionable trappings. It is no accident department stores began at this time, since manufacturing not only produced the goods, but also generated the consumers needed to buy them. Clothes, food, recreation, family vacations, all these became suitable symbols of social status.
And houseplants, too.
By the late-1800s, plant breeding had produced an affordable array of tough houseplants, and middle class homes of factory workers could decorate their homes just like the upper class (a classic use of snob appeal). Improved glass manufacturing allowed for larger windows, and homemakers could create arrangements with an expanded variety of plants. Compact gardens popped up on balconies and window ledges. Terrariums and intricate plant stands added attractive accents to these small homes, particularly in drawing rooms or parlors.

These weren’t just a subtle display of material wealth, but also moral “wealth” as well. The emulation of the upper class implied better education and etiquette. By the late-1800s, doctors had been able to prove the value of their work to society, so medical advice gained real authority. Houseplants became a subject of study during this medical boom, with some doctors believing houseplants could improve the sanitary conditions of the home and even ward off consumption (tuberculosis).
…plants and flowers, particularly when cultivated in-doors, are worthy to be placed in the foremost rank of sanitary agencies. The mass of evidence at hand relating to the subject in the author’s opinion, established the complete efficacy of living plants as preventative measure in that deadly malady, consumption of the lungs…”
~House-plants as Sanitary Agents by J.M. Anders, MD, PhD
While many health trends in this era proved pointless, there is strong evidence to these beliefs. In 1989 and (again) in 2007, NASA scientists demonstrated plants could reduce dangerous or even deadly air toxicity by 87% in less than 24 hours, literally by absorbing toxins through the soil and breaking it down to harmless molecules or elements.
Houseplants fell out of favor (again) in the 1920s, mostly as a counter-punch to the moral and social rigidity of Victorian and Edwardian culture. Worldwide economic panic and the horrors of war had worn away the appeal of Victorian posturing.