You saw a plant you loved in a shop or nursery. You brought it home, and for months it warmed your heart. But then it started to decline. What are you doing wrong? Is it dying? Can you save it?
For answers, we talked with the plant doctor: Christopher Satch, who has a master’s degree in botany from Rutgers University, teaches plant science at the New York Botanic Garden, and is involved with the Manhattan Orchid Society and the American Orchid Society. Oh, and he’s also the plant scientist for The Sill, which has two shops in Manhattan and ships houseplants nationwide.
As the plant doctor, Chris fields calls and email from people seeking advice about ailing houseplants; he also dispenses knowledge during weekly drop-in clinics at The Sill’s Upper West Side shop. The best way to keep a plant happy, he says, is to learn what it wants before you buy it—and only buy plants that suit the conditions you can offer. If you live in a ground-floor apartment with little light, say, don’t get a plant that will only thrive with tons of direct sunshine.
How can you diagnose a dying plant’s problem in time to cure it? “A lot of symptoms overlap with many causes,” says Chris. “You have to piece together the puzzle to diagnose the problem.” Here’s how to cure your plant’s ailment.
How can I tell if I am overwatering?
Symptoms: “If the leaves are turning yellow, the soil is moist, and you can see fungus growing at the base, you’re overwatering,” says Chris. Customers are sternly warned about how often their new plants will need water.
Solution: “Keep cacti and succulents in the sun, which cooks them dry very fast—that’s what they like,” Chris says. “Give these plants a dry rest, maybe a week, and then water them. Shade plants like ferns want their soil to be moist for a little while. Let them approach dryness—but then hit them with water right away.”
Prevention: No plant likes its roots sitting in water, which is why the pot needs good drainage—either a hole in the bottom or a layer of lava rocks or recycled terracotta shards (they’re porous, so they absorb excess water and slowly release it).
How do I know if my plant needs more water?
Symptoms: If leaves look droopy and are falling off, it’s a good sign that the plant’s not getting enough water.
Solution: “The goal is to saturate the soil so it’s evenly moist, and then let it dry out before watering again,” says Chris. “Most indoor plants are tropical, and they like warm water, not hot or cold.”
Chris outlines two basic watering techniques. The first: “Pour a little water into the center of the pot, let it sink in, pour a little more, and keep doing that until the soil is saturated.” How much water in all? A good rule of thumb is about a quarter to a third of the pot’s volume.
The second technique: soaking. “Put the potted plant in a sink or bowl and pour water slowly onto the top of the soil. Keep going until about a half inch of water has gone through the pot and collected in the sink or bowl. Then let the plant soak—maybe even a full day. Take it out and let it drip dry before putting it back in its planter or plate.” (This method only works when the pot has a drainage hole in the bottom—it can even be plastic.)
Prevention: “Sometimes people just dump water on the plant and it immediately flows through and comes out the bottom,” says Chris. “Your plant has not been watered—if you stick your finger into the soil you’ll see that the center of the root ball is still bone dry. That’s why soaking is important.”
Tip: That trick about putting ice cubes in the pot so the water is released slowly? Forget it.
How can I tell if my plant needs more or less sun?
Symptoms: You can blast most indoor plants with light and they’ll be fine, because the sun is much weaker when it comes through a window. But plants that prefer low light, like ferns and calathea, will be burned by too much sun—blanched leaves are a sign. On the other hand, plants that are not getting enough light may get spindly and stretched out or start dropping leaves, says Chris.
Solution: Most houseplants prefer medium to bright light. “Think of the fiddle-leaf fig, which people plant as outdoor hedges in Florida. They love the sun, and they’ll drop leaves in response to lower light.”
Prevention: Artificial light may help. If the natural light in your home is really low, artificial light can make plants happier. No bulb offers the full spectrum of light that plants need—not even the ones designed as grow lights—but using a more intense bulb will increase the effect. Chris recommends an LED or CFL (compact fluorescent) bulb (screw-in, not tubes), as long as it’s 1,000 lumens or more; either warm or cool is fine.
How can I tell if I’m fertilizing too much or too little?
Symptoms: Too much fertilizer and “your plant will get crispy edges, called salt burn, and the leaves may turn brown or black,” Chris says. “Basically, the plant will start falling apart very fast.” But too little fertilizer may cause a plant to stop thriving; fertilizer is important for longevity. “When a plant grows in nature, the soil is infinite; the roots can keep stretching out to find new nutrients,” Chris says. “But in a pot, that’s their universe and you’re essentially their god. Once the nutrients have been exhausted, the plant says ‘Uh-oh, what am I going to do?’
Solution: “You have to be their savior, and add fertilizer to provide nutrients—it’s literally a multivitamin for the plant,” says Chris. Follow the instructions on the label.
Prevention: Use crystals, liquid, or slow-release pellets as recommended.
How can I tell if the pot is too small?
Symptoms: Chris says customers email him asking, Why isn’t my plant growing? “I look at the photo and write back, ‘Do you not notice how big the plant is in relation to the pot?’ It’s like trying to jam your foot into a shoe that’s two sizes too small!”
Solution: A rule of thumb is that the volume of the plant should be two-thirds above ground and one-third below ground. The soil level should be within an inch or two of the rim, depending on the pot size, so when you pour in water it can pool before seeping in.
Prevention: When you buy a plant that comes in a plastic pot, repot it right away. “Plants are sold overgrown; they’re not meant to live in those pots. They need room to grow,” says Chris.
Tip: Don’t let your soil get too old. “Potting mix does decay and get mucky over time,” says Chris. Even if you’re fertilizing regularly, swap out some of the soil every year or two. It’s also a good opportunity to see if your plant needs a larger pot.
How can I tell if my plant needs more humidity?
Symptoms: Dry air is very bad, causing plants to crisp their leaves, says Chris.
Solution: Keep plants well away from vents, heaters, radiators, and air conditioners. To combat low humidity, he offers three pieces of advice: “Humidifier, humidifier, humidifier.” Get the largest one you can—it’s great for human health as well. If you only have a dinky one, put it right next to the plants.
Prevention: Misting can help if it’s done regularly, but as soon as the mist dries, the effect is gone. You can also group plants with similar needs to create a microclimate—but note that if you get pests, every plant will be infested.
What can I do if I see bugs?
Symptoms: Mealy bugs look like tiny white cotton balls. Other bugs look like, well, bugs.
Solution: “Using an insecticide like Raid is like using an atom bomb to knock down a house,” says Chris. “And those chemicals can hurt the plant.” He recommends washing the plant with warm water, then wiping it down to remove as many bugs as possible. Follow up with a spray of horticultural oil or insecticidal soap, being careful to reach the crevices and the undersides of the leaves.
Prevention: Keep your plant clean (dust or wipe its leaves gently) and check it regularly for bugs.
Where do I find more information about caring for my houseplant?
“Most of the time those little plastic tags you get with a plant are useless,” says Chris. Ask the person you buy it from; a good nursery should know what they’re selling. Otherwise you can always contact Chris at The Sill, search online, or send your question (with a photo) to your local botanic garden.
How can I tell if my plant is dead or salvageable?
“If it’s brown or looks dead, it probably is dead,” says Chris. But some woody plants, like the rubber tree and the fiddle-leaf fig, can recover even if they’ve died back to the stalk. “Blast it with light, give it a little fertilizer, water it when it’s dry, and it’ll say ‘Life is worth living! Let’s regrow!’ You could have the same luck with plants like pothos and monstera, as long as there’s a little vine or stem left.”
On the other hand, if a plant’s too far gone—and definitely not beautifying your home—it can be wise to cut your losses and start again with something fresh.
An encouraging word?
“Most indoor plants will do absolutely fine on a steady diet of dappled sun and water when they’re dry,” Chris says reassuringly. “Cacti and succulents need more bright light and dry soil; ferns need wetter conditions. And then there’s Sansevieria, which deserves all the respect—whether it’s under artificial light or blasted with direct sun, it’ll just keep growing.”
For more houseplant growing tips, see our curated guide to Houseplants 101: A Field Guide to Planting, Care & Design, including Prayer Plants, Fiddle-Leaf Fig Trees, and Monstera: