The first time I tramped a trail in a Costa Rican rain forest, while being buzzed by hummingbirds as thick as mosquitoes in Michigan, I looked at a vine clambering over a nearby tree and realized: Hey, that’s a philodendron. It was the same plant with heart-shaped leaves that can be found in greenhouses, fern bars and living rooms like mine worldwide.
Philodendrons (it turns out there are more than 50 species in Costa Rica) are just one of the many familiar houseplants that are native to the understory of tropical rain forests around the world. Plant hunters in the 18th and 19th Centuries brought them back to Europe for the conservatories of the wealthy. As the middle class grew and more people could afford windows and central heating, a few of the most shade-tolerant and least finicky plants trickled down into homes.
Because they come from tropical places where there’s not a lot of seasonal variation, these plants keep their leaves year-round. Because they evolved on the forest floor, beneath the shady canopy of trees, they can survive in low light. Because they come from places with poor soil and few nutrients, they can handle life in a pot. They may not be big bloomers—it’s hard to muster enough sunlight to flower in the dark forest—but they bring a welcome touch of green to the indoors and a reminder of the garden to gloomy northern winters.
Many of these plants have evolved the ability to cheat the dark by reproducing in ways other than flowering. Basically, they clone themselves. Some can root from any leaf node that touches soil, such as that philodendron vine, or pothos from Africa, or inch plant from Mexico. Others can root from offshoots that grow on the ends of searching stems, such as my kitchen spider plant from Africa. They are scrambling opportunists, ready and willing to take root in a jar of water on the windowsill.
The hardest part of life indoors, for a rain forest plant, is the lack of rain. Even in the dry season, a rain forest is a lot more humid than a centrally-heated Chicago living room. To help with the humidity, I set my houseplants up on pebbles in trays or saucers filled with water. Spritzing from a spray bottle doesn’t help much, but a humidifier does.
It’s tempting to overcompensate by watering more, but that causes more problems. These plants evolved in a deep, ancient layer of humus—decomposed plants and animals—that drains beautifully (it has to, given the constant rain, or the rain forest would be a lake). In wet soil, their roots will rot. I’m careful to only water my houseplants when their soil is dry to the touch (and barely moist an inch down), and I make sure the excess water drains away.
Since they don’t get daily showers like they would back home, these plants can get as dusty as the piano. I wipe larger, glossy leaves occasionally with plain water in the winter. In summer my plants go outdoors where they get washed by real rain.
If they receive more light, in a greenhouse or a south-facing bay window or sunroom, many of these plants will grow more lushly. But too much sunlight and they’ll shrivel up and die; they didn’t evolve for the full glare of the sun. It’s their ability to grow in low light (not none, but not much) that makes them good companion plants for people.