"I'm a serial plant killer," said Connie Tzioumis, 31, a human- rights analyst who works in Washington, D.C. "I have plants in my office. and I've killed every one. I've also killed every plant in my apartment this year."

Tzioumis' co-worker, Tara Guelig, can relate. "I'm starting to get annoyed," she said. "It's a lot of money down the drain." Guelig, 25, reels off her victims — a jade plant, a Gerbera daisy, a hydrangea — oh, and an orchid.

This death watch is familiar to many who live in apartments, where light and humidity can be painfully low: A once-lush houseplant loses its vigor and starts to wilt. Extra water and a watchful eye do nothing to reverse the decline. The plant gradually dies and, with it, a little bit of the budding gardener.

It doesn't have to be this way, as a trip to the apartment of Anastassia Solovieva and Yashar Saghai, who also live in the District of Columbia, reveals. Their small apartment is home to 20 varieties of plants, including asparagus ferns, a euphorbia and a purple passion plant.

When they lived in Paris, they assembled an indoor garden of 100 plants, including a 14-year-old palm tree.

Solovieva, 25, has a leg up on most of us because of her extensive plant knowledge: She's a landscape design student at George Washington University and works full time at a commercial garden center. But even she admits to having killed a leafy friend or two.

"You have to accept that some might die," she said, philosophically. "Also, different plants have a different life expectancy."

The key to increasing your odds with houseplants, said Solovieva, is a state of mind. View them as a serious commitment, like having a pet. "You can't just completely forget it for a while and then come back to it. With plants in apartments, you are the only thing they have for survival."

Larry Shapira, indoor plant specialist at Merrifield Garden Center in Fair Oaks, Va., says that by far the most common cause of houseplant death is improper watering. People either neglect plants and let them dry out or shower them — literally — with too much attention. Unfortunately, the early symptoms of under-watering and over-watering appear nearly identical: wilting.

One way to tell the difference: If a wilting plant does not perk up a half-hour or so after you water it, there's a good chance over-watering is the culprit and root rot has set in. "It's almost always fatal," Shapira said. "Less water is always better."

Just two or three days of over-watering are enough to kill a plant, Solovieva cautioned.

To diagnose the problem, Shapira recommends taking a plant out of its pot — it's not harmful — and inspecting the roots.

Healthy roots are white or beige; roots that are getting too much water (and are therefore starved for oxygen) are black or purple and smell bad. If your plant is suffering from root rot and its stems are soft, it's time to throw in the towel.

Improper lighting is another big problem for indoor plants. Too little light results in starvation, weakness and reluctant flowering. Too much light "could just end up burning it," Solovieva said.

Before you buy a plant, Shapira said, ask yourself what light conditions you have: Are there windows? Do you live in a basement apartment? Where do you plan to put the plant? And ask a nursery or garden center employee for advice.

Shapira recommends easy-to-maintain plants, such as a peace lily (aka spathyfillum) or dracaena, for almost any kind of light condition, although low-care plants such as a cactus or aloe may be as thirst-proof as a camel but still need bright light.

It is possible to compensate for a lack of light with a regular incandescent light bulb. "One of the easiest adaptations is to buy a light and put it on a timer" near a plant, he said.

Habitual plant killers probably should avoid most palms and orchids (moth orchids and bamboo palms are tougher). "Many people don't have the light to support them," Shapira said.

Field trips to the sunlight may not always be the best thing. "They'll burn right up," he said. "Plants need to acclimate."

Bug infestation can happen to any plant, and it's important to check often for critters, especially after the plants are brought inside after a summer outdoors.

Tzioumis admits frustration with her plant failures and is searching for "the cockroach of plants" before she resorts to an artificial version. "It needs to be able to live through the nuclear holocaust and survive," she said. "That's the kind of plant I need."

Shapira has just the plant — a philodendron: "They're tough to kill," he said. "They really are."