The secret to keeping plants alive is to recognize what’s killing them and fix it fast. This checklist describes the most common houseplant killers, helps you recognize symptoms, and explains how to apply a remedy before it’s too late.

1. Overwatering. This is the single most common cause of death for houseplants and generally happens for one of two reasons. Most often, we’re overly affectionate, giving plants too much of what they need. Sometimes, we’re overly efficient, regularly, but lethally, giving every plant the same amount of water on the same schedule.

Symptoms. The earliest symptom of overwatering may be as obvious as puddles in the plant saucer. One of the most reliable—but less easy to recognize—signs that you’ve been killing your plant with kindness is a generalized yellowing of the leaves. Sometimes the leaf tips turn black and the yellow leaves fall. As the damage progresses, your plant may sprout brown to black fungal spots on the yellow leaves. If you’ve turned a blind eye to all of this, the plant will eventually collapse and die because its entire root system has rotted away. A foul odor in the plant mix is another sign that the roots are rotting.

Cures. If you’ve overwatered your plant on a single occasion, just pour off any standing water, allow the soil to dry out again, and the plant will be fine. But if you notice advanced symptoms, you’ll need to give it some help drying out. Gently inspect the soil and roots; if the soil is especially mushy and the plant has a reasonably well-established root system, lift it out and put the root ball directly on a stack of newspapers, which will draw out the moisture. If the plant is young, or not that wet, just put the pot (which, of course, has a drainage hole in the bottom!) on newspapers and change them as needed. After drying the plant, disinfect the pot to get rid of any accumulated fungus; otherwise the roots may rot again, however carefully you water.

How much is too much? Most plants like to be watered when the soil is dry about a third of the way down the pot. You can buy a plant meter at the nursery, but any of the low-tech methods like twisting a pencil or your finger deep into the soil will also be a fairly reliable indicator of the moisture level. But check the instructions that come on the plant, or ask the expert at the store if the plant you’re buying has special watering requirements.

2. Underwatering. This can happen if you’re away on vacation, distracted, or forgetful. But the most common cause of parched plants is watering them on a set timetable. “Do not put your plants on a watering schedule,” warns houseplant specialist Vivian Mitchell of Merrifield Garden Center in Merrifield, Virginia. “Water only as plants request watering,” she advises. Plants make their initial request for watering by drooping slightly.

Symptoms. A thirsty plant wilts and perks again when watered. The leaves of a chronically dry plant (one that gets some water, but not enough) will turn brown along the leaf margins and out to the tips. This is a sign that the dehydrated soil has accumulated too much salt and the plant tissue has burned. Older leaves will turn yellow and drop from the bottom of the stalk as their nourishment is sucked away to feed new growth. Note the contrast with overwatered plants, which turn black only at tip of the leaf and have generalized, not localized, yellowing.

Cures. Water the plant when it’s dry about one third down from the top. And check with an expert to make sure this is exactly what each plant requires. Some plants need to be kept moist all the time and some like to dry out thoroughly between watering.

3. Overpotting. Just as you wouldn’t buy a pair of shoes three sizes too big and wait to grow into them, you shouldn’t put a small plant in an enormous container and expect it to grow into the pot. Your plant will be uncomfortable in its “big shoes”; it won’t thrive and may even die. Plants prefer containers that allow them to extend their roots throughout, pulling in moisture and nutrients from every corner. When you attempt to keep the soil moist in a big pot with tiny roots, there is greater danger of rot because the water displaces the soil’s oxygen, causing the root system to stagnate.

Cures. Keep a new plant in the container it comes in unless you see roots growing right out the drainage holes. When you do repot, choose a container that is only one or two sizes larger than the old one.

4. Wrong soil. The general rule is to use only professionally produced potting medium—never “dirt” from the garden or any other dense or heavy soil. When you purchase plants at a nursery or garden shop, they are planted in the right mixture. When you’re repotting, use only soil marked “houseplant potting medium” for the job, and use fresh soil; never recycle soil from another plant.

5. Wrong light. You must know the requirements of your individual plants to get this one right. If the plant didn’t come with instructions, look in a plant book or call a nursery and ask.

Symptoms. Flowering plants (African violets, cyclamen, poinsettias, cactus) usually need a high amount of light to bloom and won’t flower without it. Plants that tolerate only low light will burn and develop an all over yellow-to-brown look if left in direct sun or in a very bright room. Nonflowering houseplants that get too little light may lose color and drop leaves; or they may become leggy as the plant stretches toward the light.

Cures. Those blue “plant-grow” light bulbs are fine to supplement inadequate daylight. But exclusive use of artificial incandescent bulbs will focus too much warmth on the plant. If you are really short of daylight, use a fluorescent bulb in combination with the plant bulbs. Don’t expose any plants to light for more than twelve hours at a time. If a plant shows symptoms of too much light, move it!