A houseplant is a plant that is grown indoors in places such as residences and offices. Houseplants are commonly grown for decorative purposes, positive psychological effects, keeping fresh or health reasons such as indoor air purification.
Houseplants need the correct moisture, light levels, soil mixture, temperature, and humidity. As well, houseplants need the proper fertilizer and correct-sized pots.
Both under-watering and over-watering can be detrimental to a houseplant. The best way to determine whether a plant needs water is to check the soil moisture. Feeling the soil is most reliable, since moisture meters are often inaccurate. Most potted plants must be allowed to reach an appropriate level of dryness in between waterings, though the amount of watering required varies greatly depending on the species. Proper soil moisture can range from still slightly moist on the soil surface to very dry to nearly the bottom of the pot. Watering a plant by the calendar is not recommended. If a plant does need to be watered, water should be slowly poured over the surface of the soil until it begins to drain out the bottom of the pot, ensuring complete saturation. However, sometimes the soil separates from the sides of the pot if it is allowed to dry out thoroughly, allowing the water to flow down the sides of the rootball and out the bottom too quickly to be absorbed and retained by the soil and roots. If this is the case, it may be necessary to set the plant in a shallow dish of water long enough for it to soak up enough water to moisten the rootball to its center. Repotting should eliminate this problem. Repotting should be done only when necessary, since the roots of a plant that is in an excessively large pot may rot.
Most houseplants are tropical species selected for their adaptation to growth in a climate which ranges from 15 °C to 25 °C (60 °F to 80 °F), similar to the temperature in most homes. Temperature control for other plants with differing requirements needs attention to heating and/or cooling.
Humidity is slightly more difficult to control than temperature. The more commonly used houseplants have established that they can survive in low humidity environments as long as their roots are kept properly irrigated. Most plants thrive in 80% relative humidity while most homes are usually kept around 20% to 60% relative humidity. Besides buying a humidifier, there are a few things that can be done to increase humidity around houseplants. The most popular methods used to raise the ambient humidity are misting and pebble trays, which are shallow trays covered with pebbles and filled with water that evaporates to increase humidity. Other methods of raising humidity include grouping plants closely together and not placing plants in drafty areas. Misting has become controversial among gardeners and horticulturists, some of whom will point out that it seldom provides moisture in the form of water vapor, and that, instead, by wetting the leaves it increases disease problems.
In a potted environment, soil nutrients can eventually deplete. Adding fertilizer can artificially provide these nutrients. However, adding unnecessary fertilizer can be harmful to the plant. Because of this, careful consideration must be taken before fertilizing. If a plant has been in the same potting mix for a year or more and is no longer thriving, then it may be a candidate for nutrient replacement done by using a complete fertilizer at half the recommended label dilution rate.