A Practical Houseplant Care Guide

Quick answer: Put each plant where the light suits it, wait until the mix is dry about two inches down before you water, grow it in a pot with drainage holes and fertilize sparingly while it is putting out new growth. Being mostly tropical or subtropical, houseplants also want steady warmth and moister air than a heated winter home offers.

That goes for a supermarket pothos and for the rarities on our list of the most expensive houseplants ever sold.

Start With Light

Light is the usual limit for an indoor plant. Leaves run photosynthesis on it, the process behind the oxygen we cover in what plant produces the most oxygen. Here is roughly what the ratings on plant tags mean at your windows.

Snake plant, peace lily and Chinese evergreen get by in low light. Medium light is right for spider plant, rubber plant and peperomia. High light is what cacti, succulents, citrus and most flowering plants need. For anything else, see this houseplant lighting list from Illinois Extension.

Too little light shows as long, skinny stems bending toward the glass, older leaves falling and pale color. Too much leaves scorched or bleached patches. When no window fits, an indoor grow light can supply what is missing.

Water When the Soil Says So

Light, warmth, humidity, pot size and mix all change how fast a pot dries, so skip fixed watering days.

1. Slide a finger about two inches into the mix. Most foliage plants need water once it is dry that deep.
2. Pour slowly until water drains from the holes in the bottom.
3. Tip out the saucer. A pot should never sit in standing water.

Ferns and "keep evenly moist" plants need water sooner, while cacti, succulents and plants in dim spots go longer. Bottom watering works too. Let the pot soak up water from a shallow basin until the surface turns damp.

Use room temperature water, never cold or softened. Unglazed clay loses moisture faster than plastic, so check it more often. And feel the soil before rescuing a droopy plant, because overwatering causes wilting too.

A pot with no drainage hole keeps the mix soggy and leads to root rot. Use a holeless decorative pot only as a sleeve around a nursery pot, and empty any water that pools.

Pick a Pot and Mix That Drain

Buy bagged potting mix, since garden soil drains badly in pots and may carry insects and disease. A blend with equal thirds of sterilized bagged soil, peat moss and either perlite or vermiculite is a good all-purpose choice. A soilless mix is fine, but it holds almost no nutrients, so you will need to feed more.

When and How to Repot

Repot in spring or early summer when roots poke out the holes or creep over the soil, the root ball is a solid mass, new leaves come in smaller, or the plant wilts between usual waterings.

1. Choose a pot only 1 to 2 inches wider. An oversized pot holds water too long.
2. Gently loosen any circling roots.
3. Set the plant at its old depth, with some space under the rim.
4. Water it straight away.

Scrape off the top inch if white salt has crusted on the old soil.

Humidity and Temperature

Most houseplants like relative humidity between 40 and 60 percent, and some tropical types want more. Heated homes often drop under 30 percent in winter, and crisp, brown leaf edges are the usual clue. Cacti and succulents cope with dry air.

Don't humidify the whole house, though. The EPA advises keeping indoor humidity under 60 percent, ideally 30 to 50, to hold back mold, and wet windows mean the air is too damp. Add moisture near the plants instead.

• Run a small, clean humidifier nearby and track the level with a hygrometer.
• Cluster plants so their moisture stays near them.
• Use a pebble tray with pot bottoms above the water, for a modest gain.

Misting helps briefly and can invite disease if overdone. Foliage plants like 65 to 75°F in daylight, a drop of 5 to 10 degrees overnight, and a spot away from drafty doors, radiators, heating and cooling vents and cold glass.

Fertilize Lightly in the Growing Season

Feed only during active growth. From March to September that means roughly every 1 to 3 months, and in winter little or nothing. A plant you just brought home can skip its first few weeks.

Use a houseplant fertilizer like 10-20-10 or 10-10-10, never stronger than the label says. Too much burns roots and harms slow growers in low light. Every 4 to 6 months, flush the pot with plenty of plain water and let it all drain to rinse out built-up salts.

Catch Pests Early

Quarantine a new plant for two weeks to a month and look it over under the leaves, at the joints and on the soil. Wash hands and tools between groups of plants.

• Spider mites leave fine webbing and yellow leaves. Rinse with water, then spray insecticidal soap under the leaves at least twice, 10 days between treatments.
• Mealybugs look like white cotton in leaf joints. Dab them off with rubbing alcohol on a cotton swab.
• Scale shows as brown, shell-like bumps with sticky leaves and black sooty mold. Wipe with a soft cloth and mild soapy water, then again three weeks later.
• Aphids bunch on buds and new shoots and leave leaves shiny. Hose them off or wipe with alcohol.
• Fungus gnats are small, delicate flies with larvae in wet soil. Let the mix dry out more between waterings.
• Whiteflies are tiny, white and moth-like and hide under leaves. Treat with a spray or a dip once a week, keeping it up for several weeks.

A soapy wash is one teaspoon of mild liquid soap per gallon of water. Even insecticidal soap hurts some plants, so check the label.

Pets and Toxic Plants

Several popular houseplants are poisonous to cats and dogs. Insoluble calcium oxalates in pothos, peace lily and anthurium mean a pet that chews them may drool, vomit, struggle to swallow and have an irritated mouth. Snake plant can lead to nausea, vomiting and diarrhea.

Lilies are the big danger for cats. True lilies (Lilium) and daylilies (Hemerocallis) can damage a cat's kidneys to the point of failure, and pollen or vase water is enough. With a cat at home, keep them out completely, bouquets included.

Spider plant, Boston fern and prayer plant appear on the non-toxic list for cats and dogs, though any plant a pet eats can still cause a stomach upset. Check a new plant on the ASPCA toxic and non-toxic plant list before buying, and phone your veterinarian at once if a pet chews something toxic.

Putting It Together With Anthurium

Anthurium, sold as flamingo flower, shows how this works on one plant. The showy spathe is technically a leaf, and the spike of tiny flowers in it is the spadix.

• Light. Medium light keeps it going, and bright, indirect light gives the most blooms. Pale, faded leaves often mean too much light, not a lack of fertilizer.
• Water. Let the mix dry a little, then water deeply.
• Mix. Coarse and quick to drain, like peat, perlite and bark in equal amounts.
• Warmth. Between 70 and 85°F, never under 55°F, away from drafts and appliances.
• Food. Go easy, since extra fertilizer leaves salts that burn leaf tips and edges.
• Upkeep. Snip off faded blooms, repot once roots fill the pot and divide it for more plants.
• Handling. Anthurium is poisonous to pets and its sap is a mild irritant, so wear gloves to prune or divide.

Common Questions

How Do Succulents Reproduce?

Many grow offsets, little plants beside the parent that you cut free once they have roots. Many also root from a leaf or stem cutting left to dry and callus before planting.

How Do I Propagate a Vining Houseplant?

Take a stem tip 3 to 6 inches long with two or more nodes and root it in damp perlite or potting mix in bright, indirect light. Roots grown in water have a harder time adjusting to soil later.

Which Houseplants Grow the Fastest?

Almost any of them grows quicker with more light, up to the most that plant tolerates. Expect slower growth through the dark winter months.