As winter grows dark and the weather gets gloomy, it’s time to acquire some companions that will change your mood: houseplants.

Research indicates that indoor plants can reduce stress and boost happiness. And beyond their outlook-improving powers, many verdant beauties claim air-purifying properties, too.

“People don’t realize that indoor pollution is often several times higher than the pollution outside,” says Donna Zagrapan, a horticulture specialist and former Penn State master gardener. “Plants become a simple and pleasant solution to alleviate that problem.”

Not all plants, however, are created equal. As Zagrapan noted at a recent Plants for Indoor Air Quality workshop at Greensgrow Farms, while most simply carry out the give-and-take of oxygen for carbon dioxide, some plants absorb toxins, too.

So which indoor varieties maximize your returns? The NASA can answer that.

Following a 1989 study to determine the best ways to clean the air in space stations, the government agency published a report on plants proven to purify the air. Researchers identified 29 species and varieties that remove common airborne chemicals, specifically benzene, formaldehyde, trichloroethylene, xylene, and ammonia — all of which are linked to health issues ranging from headaches and eye irritation to heart problems.

Zagrapan notes that these chemicals are omnipresent in our homes, emitted as gases from various solids or liquids such as paint, rubber, floor wax, plywood paneling, and cleaning supplies. It makes her appreciate the understated capabilities of plants all the more.

“The idea that a plant can actually take these poisons out of the air — Mother Nature is just incredible.”

Below, Zagrapan shares the 10 NASA-endorsed, air-purifying plants that are easiest to sustain indoors.

The first seven will thrive even in low-light conditions, meaning that while you will need at least one small window in the room, direct sunlight isn’t necessary. The latter three — aloe and two types of ferns — are only slightly more demanding.

Zagrapan recommends one 4- to 6-inch plant for every 100 square feet of your home. The larger the plant, the more toxins it will absorb. And she has a clear favorite: “There is one plant — only one — that collects every single toxin that NASA studied, and that is the peace lily,” she says. “Everyone should have a peace lily.”

LOW-LIGHT TOLERANT

Peace lily
Grace Dickinson / STAFF
Peace lily

Peace lily

  • Absorbs benzene, formaldehyde, trichloroethylene, xylene, and ammonia
  • Prefers temps above 60 F, ideally above 70 F (keep away from drafty windows)
  • Prefers bright, indirect light; can survive in low-light conditions
  • Is toxic to pets
English ivy
Grace Dickinson / STAFF
English ivy

English ivy

  • Absorbs benzene, formaldehyde, trichloroethylene, and xylene
  • Does well in cool temps, by drafty doors and windows
  • Not light-sensitive; can survive in sun and shady corners
  • Is toxic to pets
Snake plant
Grace Dickinson / STAFF
Snake plant

Snake plant

  • Absorbs benzene, formaldehyde, trichloroethylene, and xylene
  • Prefers temps above 50 F
  • Does well in shady corners and can handle some direct sunlight
  • Is toxic to pets
Devil's ivy
Grace Dickinson / STAFF
Devil's ivy

Devil’s ivy (a.k.a. money plant, pothos)

  • Absorbs benzene, formaldehyde, and xylene
  • Prefers temps between 60 F and 80 F
  • Prefers bright, indirect light; can survive in low-light conditions 
  • Is toxic to pets
Spider plant
Grace Dickinson / STAFF
Spider plant

Spider plant

  • Absorbs formaldehyde and xylene
  • Prefers temps between 55 F and 80 F
  • Prefers bright, indirect light; can survive in low-light conditions; 
  • Is not toxic to pets
Elephant ear philodendron
Grace Dickinson / STAFF
Elephant ear philodendron

Elephant ear philodendron

  • Absorbs formaldehyde
  • Prefers temps between 65 F and 75 F
  • Prefers bright, indirect light; can survive in low-light conditions
  • Is toxic to pets
Heartleaf philodendron
Grace Dickinson / STAFF
Heartleaf philodendron

Heartleaf philodendron

  • Absorbs formaldehyde
  • Prefers temps between 60 F and 75 F
  • Prefers bright, indirect light; can survive in low-light conditions
  • Is toxic to pets
Aloe
Grace Dickinson / STAFF
Aloe

WINDOW LIGHT REQUIRED

Aloe

  • Absorbs benzene and formaldehyde
  • Prefers temps between 55 F and 80 F
  • Requires bright, indirect light; does best in south- and west-facing windows
  • Can go weeks in between watering
  • Is toxic to pets
Boston fern
Grace Dickinson / STAFF
Boston fern

HUMIDITY REQUIRED

Boston fern

  • Absorbs formaldehyde and xylene
  • Must have a humid environment, like a bathroom
  • Prefers temps between 55 F to 75 F
  • Prefers lots of indirect light
  • Is not toxic to pets

Kimberly Queen fern

  • Absorbs formaldehyde and xylene
  • Must have a humid environment, like a bathroom
  • Prefers temps between 60 F to 80 F
  • Prefers lots of indirect light
  • Is not toxic to pets