Houseplants: Nature’s air purifiers

While many people keep houseplants for their beauty, some also have a beneficial effect on indoor climate. By cleaning the air of toxins, reducing mould, and increasing a room’s oxygen content, plants can increase the well-being of a home’s occupants while reducing allergies and other negative effects of polluted air. In addition, plants can absorb excess moisture in indoor air, releasing it via transpiration1 when needed. This helps maintain a healthy indoor humidity level, which helps keep allergens like dust mites to a minimum.

These are some of the best plants to bring into your home for both health and beauty.

This spiky marvel has been renowned for its many medicinal uses for 6,000 years — going back to ancient Egypt, where it was known as the plant of immortality. Besides soothing a burn and taming acid reflux, it acts as an air filter.

• Toxins Removed: Formaldehyde, benzene
• Toxic to Pets: Yes
• Care Level: Easy
• Cost: Inexpensive
• Care Tips: Water Aloe Vera plants deeply, but in order to discourage rot, allow the soil to dry at least 1 to 2 inches deep between watering. Water about every 3 weeks and even more sparingly during the winter. Use your finger to test dryness before watering.

This small palm from Madagascar is widely acknowledged as the heavyweight champion of air purification. As it grows larger, the areca palm acts as an air humidifier by transpiring moisture into the surrounding space. In fact, a five-foot tree can release over one litre of water in a 24-hour period! This is especially beneficial in the winter, when HVACs dry the air.

It’s one of the plants most studied by NASA in a search for ways to purify air during extended space missions.

• Toxins Removed: Formaldehyde, xylene, toluene, and more
• Toxic to Pets: No
• Care Level: Easy/Medium
• Cost: Moderately Priced
• Care Tips: Care of Areca palms indoors isn’t difficult, but the plant won’t tolerate neglect. Water them often enough to keep the soil lightly moist in spring and summer, and allow the soil to dry slightly between watering in fall and winter. Fertilize areca palm plants with a time-release fertilizer in spring.

It’s delicately marbled, almost heart-shaped leaves give this plant a beautifully unique look. It’s perfect for hanging baskets, where if you pinch back the runners it will stay bushy. This type of plant is relatively easy to grow, but in terms of clean air its big selling point is a high transpiration rate.

• Toxins Removed: Benzene, formaldehyde, trichloroethylene, xylene, and ammonia
• Toxic to Pets: Yes
• Care Level: Easy
• Cost: Moderately Priced
• Care Tips: Overall, arrowhead plant care is quite easy. It should be allowed to dry out between watering. Although the plant enjoys some moisture, it should not be kept too wet, which may lead to root rot. It prefers temperatures between 60 and 75 F (16 and 24 C.) but can tolerate a wider range, if necessary. Proper arrowhead plant care requires humid conditions, especially during dry winter months. Mist the plant daily or place its container on a tray filled with pebbles and water to increase humidity for optimal growth. The arrowhead plant can be fertilized monthly with a balanced fertilizer.

Native to Mexico and Central America, this small palm thrives in shady indoor spaces. It can grow to a maximum height of two metres, and often produces flowers and small berries. When it comes to air filtration, the bamboo palm is among the most effective houseplants.

• Toxins Removed: Benzene, trichloroethylene, formaldehyde
• Toxic to Pets: No
• Care Level: Medium Difficulty
• Cost: Moderate to Expensive
• Care Tips: Keep the bamboo palm moist, but never overwater. Soggy soil leads to root rot. Water enough to keep the soil moist. Pour water from the drainage tray after watering. Only water when the soil feels dry and allow the soil to dry out in between watering in the winter.

Ferns can be difficult to maintain, but not the hardy Boston fern. This popular houseplant looks great in a hanging basket and absorbs formaldehyde more effectively than any other known air-purifying plant.

• Toxins Removed: Formaldehyde, xylene, benzene
• Toxic to Pets: No
• Care Level: Easy to Medium Difficulty
• Cost: Inexpensive
• Care Tips: Make sure that it’s in the right kind of environment. Boston ferns need a cool space with high humidity and indirect light. When you care for Boston fern plants indoors, it’s a good idea to provide additional humidity for them, especially in the winter, otherwise the leaves will dry quickly and shed.

This tropical plant isn’t choosy: It thrives in places where other plants won’t grow. Even in low light, it produces blooms and berries. It does prefer humidity to dry air. The Chinese evergreen’s air-purifying abilities increase with time and continued exposure to toxins.

• Toxins Removed: Benzene, formaldehyde
• Toxic to Pets: Yes
• Care Level: Easy to Medium Difficulty
• Cost: Expensive
• Care Tips: Allow the plant to dry out some between watering. Overwatering will lead to root rot. As part of your Chinese evergreen care, you should fertilize older plants once or twice yearly using a water-soluble houseplant fertilizer.

Left to its own devices, this tropical flowering plant reaches about 1.5 metres tall, but with regular pruning and trimming you can keep it smaller and in any shape you like. Some people even grow it as a bonsai.

This plant requires little care and can live for 20 years. To maximize its effectiveness as an air cleaner, wipe off the leaves each month to keep dust from clogging their pores.

• Toxins Removed: Benzene
• Toxic to Pets: Mildly toxic
• Care Level: Medium Difficulty
• Cost: Expensive
• Care Tips: The ideal setting for a dwarf umbrella plant is directly in front of an east-, west- or south-facing window with a sheer curtain hanging between the plant and window to diffuse the direct sunlight. Direct sunlight will scorch an umbrella plant’s leaves, and they will turn yellow and drop. Average room temperatures of 65 to 75 °F (18 to 24 °C) are ideal, although the dwarf umbrella plant will do fine with temperatures up to 85 °F (29 °C). Average room humidity is usually fine for this plant, but if the house tends to get dry from heating or cooling, mist it each morning with room temperature water. Water the plant when the soil becomes dry or the leaves begin to wilt, using aged water. Fill the watering container a few days before watering the plant and leave it uncovered. This will allow the chlorine to dissipate, and the water will be at room temperature. This is a tropical plant that can be stressed by fresh, cold tap water. If the leaves become wrinkled, the plant is not getting enough water. If it is being overwatered, the leaves will turn black and drop.

You have likely seen this climbing vine outdoors because of its popularity in landscaping and tendency to spread aggressively. It’s so invasive that horticulturists advise caution when planting English ivy outside, but it makes a great indoor plant. It’s proficient at cleaning the air and easy to maintain.

• Toxins Removed: Benzene, formaldehyde, xylene, toluene, mould
• Toxic to Pets: Yes
• Care Level: Easy
• Cost: Inexpensive
• Care Tips: To maintain the bright color of a variegated ivy, give it plenty of light. Ivies can be grown with artificial light, or near a north, east or west window. Water ivies thoroughly, then let the soil dry to the touch to a depth of ½ inch before watering again.

The garden mum originated in China and belongs to a large family of flowering plants, many of which are staples of summer gardens. Garden mums come in hundreds of varieties, and plant breeders are always creating more.

• Toxins Removed: Benzene, formaldehyde, xylene, toluene, trichloroethylene, ammonia
• Toxic to Pets: Yes
• Care Level: Medium
• Cost: Inexpensive
• Care Tips: Give them as much sun as you can. Mums will thrive in full sun conditions, given adequate moisture. About three hours of direct sunlight is about the minimum that will produce bushy plants and plenty of flowers. Early in the season mums should be watered like your lawn, about one inch a week. Regular watering is a crucial part of indoor mum care. Water the plant from under the leaves to help prevent fungal issues when caring for container mums. Deadhead if you wish, to keep the plant looking its best. Keep chrysanthemum houseplants where they can receive good air circulation and avoid excess humidity.

This green and yellow vine is native to the Soloman Islands, but grows all over the world. It’s among the most popular houseplants because it grows quickly and requires very little care. Even beginners can easily start one from a cutting.

• Toxins Removed: Benzene, formaldehyde, xylene, toluene
• Toxic to Pets: Yes
• Care Level: Easy
• Cost: Inexpensive
• Care Tips: Try not to soak the soil but instead water lightly around the pot. Reduce the frequency and amount of water to light or moderate watering in winter. Golden Pothos is a very stable houseplant so applying a balanced (20-20-20) fertilizer monthly will suffice. Use a soil-based potting mix when potting indoors.

The peace lily may look dainty, but it’s a powerhouse of toxin absorption. This plant prefers low-light areas. A typical peace lily sends up only a few flowers at a time. Peace lilies bred for sale often have been treated with a plant hormone to make them flower more. You can encourage your peace lily to flower naturally by increasing its light exposure; however, avoid direct sunlight. This can cause the leaves to burn.

• Toxins Removed: Benzene, formaldehyde, xylene, toluene, trichloroethylene, ammonia, mould
• Toxic to Pets: Yes
• Care Level: Easy
• Cost: Moderate to Expensive
• Care Tips: Give them evenly moist, well-drained soil and temperatures of at least 55 degrees. If peace lilies wilt every two to three days, repot them in larger containers, which don’t need watering as often. Fertilize plants growing in bright light about every six weeks with a liquid 20-20-20 product.

The calathea comes in many colorful, eye-catching varieties. Besides its looks, this plant has another exceptional feature: The leaves open and close, which sometimes makes a rustling sound. Small “joints” between the leaves and stems are affected by light and cause the plant to close in darkness, and then open again in brighter surroundings. This slow grower eventually tops out at just under one metre.

• Toxins Removed: Formaldehyde, benzene
• Toxic to Pets: No
• Care Level: Medium Difficulty
• Cost: Inexpensive/Moderate
• Care Tips: Use distilled water, rain water, or allow your tap water to sit out over night before using. Keep the soil of a Calathea Plant moist but never soggy. Allow the top 2-3” (25 to 50 mm) to dry out before watering. Never let a Calathea Plant sit in water.

Technically a ficus, the rubber plant will grow tall within a few years. You might think this hardy plant gets its name from the rubbery leaves, but “rubber” actually refers to the milky, latex-like sap that oozes from leaves and stems if they are cut.

Dr. B.C. Wolverton, one of the scientists involved in the NASA Clean Air Study, ranks the rubber plant as one of the very best at cleaning indoor air. It also scores high on resistance to pests and diseases, and its high transpiration rate means the rubber plant is a good choice for boosting humidity in a room.

• Toxins Removed: Formaldehyde
• Toxic to Pets: Yes
• Care Level: Medium Difficulty
• Cost: Expensive
• Care Tips: During the growing season, it needs to be kept moist. It is also a good idea to wipe off the leaves of your rubber tree houseplant with a damp cloth or spritz it with water. If you water the rubber tree plant too much, the leaves will turn yellow and brown and fall off.

This evergreen perennial plant belongs to the Asparagaceae family of plants commonly found in Nigeria and the Congo. It’s popular around the world, and with good reason. It’s among the top air-cleaning plants rated by NASA study, and extremely tolerant of low light to boot. Even nongardeners can maintain this plant and benefit from the large amounts of oxygen it emits at night.

• Toxins Removed: Benzene, carbon monoxide, formaldehyde, xylene, toluene, trichloroethylene, and more
• Toxic to Pets: Yes
• Care Level: Medium Difficulty
• Cost: Expensive
• Care Tips: Allow soil to dry between watering and take extra care not to over water in winter. Try to avoid getting leaves wet when watering. Place your snake plants in indirect light (although they are tolerant of a variety of light conditions) and fertilize during the growing season with an all-purpose plant food.

These resilient plants can adapt to just about any environment and don’t need a lot of attention. They like dry soil, but regular misting will keep away pests like spider mites and aphids.

With lots of rich foliage and tiny white flowers, the spider plant is also easy to regrow. Just cut off one of the “spiders” and place it in a pot.

• Toxins Removed: Formaldehyde, carbon monoxide, xylene, toluene
• Toxic to Pets: No
• Care Level: Easy
• Cost: Inexpensive
• Care Tips: During initial growth, water occasionally; once fully developed (within one year), water moderately. In the spring and summer months, keep the soil moist to encourage growth. Fertilize up to twice a month in the spring and summer, however, avoid over-fertilization.

When it comes to cleaning the air, this plant shines. Absorbing benzene seems to be its specialty. The dracaena also ranks high in transpiration, so you can enlist its help in humidifying a room.

• Toxins Removed: Benzene, formaldehyde, trichloroethylene
• Toxic to Pets: Yes
• Care Level: Medium Difficulty
• Cost: Expensive
• Care Tips: Direct sun burns the leaves of a Striped Dracaena. They like to be kept on the dry side. Water well and then allow the top 50% of the soil to dry out before watering again. Dark brown leaf tips are a sign of over-watering or extreme under-watering.

Native to Australia and Southeast Asia, this evergreen plant doesn’t need much maintenance with the right conditions. It likes warm temperatures, humidity, well-drained soil, and indirect sunlight. When deciding where to place your ficus benjamina, keep in mind that it can grow up to three metres tall.

• Toxins Removed: Formaldehyde, xylene, toluene
• Toxic to Pets: Yes
• Care Level: Medium to Difficult
• Cost: Expensive
• Care Tips: Plant the ficus in a well-draining potting mix, and keep it in a high-light area. Rotate the plant periodically so it grows evenly. Water weekly during the summer months using room-temperature water. Use a general-purpose fertilizer in the summer, and prune the ficus to control growth. Ficuses are temperamental and will drop their leaves when they sense an environmental change. Usually, they will grow back once the plant has become accustomed to the new conditions.

Erik Rosen is a former copywriter, journalist, and medical writer. He is currently the Director of Programs for the Building Biology Institute.

Andrew Guido is the President & Founder of Erth. He is a Certified Building Biologist and Circadian (Lighting) Wellness Auditor.