— Erma Bombeck
A houseplant is a plant that is grown indoors, such as residences and offices, namely for decorative purposes. Studies have also shown them to have positive psychological effects and as well as help with indoor air purification, since some species, and the soil-dwelling microbes associated with them, reduce indoor air pollution by absorbing volatile organic compounds including benzene, formaldehyde, and trichloroethylene.
While generally toxic to humans, such pollutants are absorbed by the plant and its soil-dwelling microbes without harm. Common houseplants are usually tropical or semi-tropical epiphytes, succulents or cacti. Houseplants need the correct moisture, light levels, soil mixture, temperature, and humidity. As well, houseplants need the proper fertilizer and correct-sized pots.
A 2015 study showed that active interaction with houseplants "can reduce physiological and psychological stress compared with mental work".
The phenomenon of biophilia explains why houseplants have positive psychological effects. Biophilia describes humans’ subconscious need for a connection with nature. Having plants in indoor living areas can have positive effects on physiological, psychological and cognitive health.
Humans enjoy looking at things that are not boring but also not too complex. The presence of plants and nature-inspired designs is restorative and not dull like the modern cookie cutter designs.
Both under-watering and over-watering can be detrimental to a houseplant. Different species of houseplants require different soil moisture levels. Brown crispy tips on a plant's leaves are a sign that the plant is under-watered. Yellowing leaves can show that the plant is overwatered. House plants need drainage in the pots because if the water builds up at the bottom of the pot, mold and root rot can occur.
Different plants require different amounts of light, for different durations. Photoperiodism is a consideration, since some plants such as Poinsettia and Schlumbergera are influenced by either decreasing or increasing daylight hours. It is possible to supplement window light with artificial lighting of suitable wavelengths
Most houseplants are tropical evergreen species that adapted to survive in a tropical climate which ranges from 15°C to 25°C (60°F to 80°F) year-round. This is similar to the temperature in most homes.