Hydrangeas do not like this weather. Neither do delphiniums, larkspur or maple trees. Boxwood and lavender can deal with it, but don't expect them to look their best.

All sorts of plants are drooping and dying during this summer's heat and drought, and the result is not pretty for landscapers or their customers.

"After the last heat wave, things are dropping right and left because of the drought and heat," said Lisbeth Prins, owner of Plant-A-Plant Landscaping Co. in Loudoun County. "It's put a kibosh on quite a few things."

And the heat is back again. Temperatures were in the mid-90s yesterday, and today's forecast is about the same. With the high humidity, it will feel as though it's 100 to 105 degrees, the National Weather Service said.

The Weather Service's urban heat advisory is likely to remain in effect until tomorrow, and the Metropolitan Washington Council of Governments has issued a "code red" advisory indicating poor air quality.

So instead of putting annuals and perennials in the ground, landscapers are spending most of their time and resources simply trying to keep them alive. Landscaping is a booming industry in the Washington area--every new home is a job opportunity--and these lost plants mean a loss in profits and labor for the landscapers, as well as disappointment for their clients.

Most companies provide a one-year warranty that requires them to replace plants that don't survive. Despite efforts to educate customers about how to properly water plants, landscapers are receiving a bevy of calls about trees and flowers that have perished and need to be replaced.

A typical suburban lawn costs $10,000 to $20,000 to adorn, landscapers say, while plants range in price from $10 for the low-end foxglove to more than $500 for a Japanese red maple. Price tags for exotic trees or shrubs run into the thousands. In these adverse weather conditions, that can add up to a lot of lost time and money.

Michael and Karen Davis, for example, had to have Plant-A-Plant return to their Ashburn home last week after two white dogwoods, two thyme plants and one stewartia, all of which were planted in March, died. One of the dogwoods died from too much water, a problem that landscapers say accounts for as many replacements as under-watering because people overcompensate for the dry weather.

The Davises use an in-ground irrigation system, but "one of the dogwoods was right by a drainage," Karen Davis said. "Whenever we would water, it collected right there." So the dogwood was replaced with a water-loving cypress, and the settings on the irrigation system were adjusted to prevent other plants from drowning.

In Southern Maryland, where the drought follows months of similarly desertlike conditions last summer and fall, replacing plants has become a particularly time-consuming and costly problem.

"Some of the crews come back every day with plants they're already replacing," said Bob Wentworth, one of four brothers who own Wentworth's Nursery in St. Mary's County. The weather has knocked profits down 15 to 20 percent, Wentworth said.

At Middleton Manner Nurseries in Waldorf, which grows flowers, trees, shrubs and sod, several costly measures have been taken to keep the extensive inventory alive. New wells, with a total price tag of $14,000, have been drilled. Irrigation pipes have been added, and two men spend their days moving the pipes around the fields so that everything gets the inch of water a week it needs.

"This is absolutely the worst drought in my lifetime," said John Roberts, 58, general manager of the nursery.

Unlike the plants, sod does not come with a warranty, so sales have fallen off considerably. "We tell anybody who wants to put down sod now that it's not the best time," Roberts said. "I wouldn't guarantee a blade of grass this time of year."

Developers, however, cannot afford to wait for the weather to change, so many continue to landscape no matter how hot it gets.

"We obviously can't put off the landscaping too long," said Dee Minich, spokeswoman for Washington Homes, which builds houses and subdivisions throughout Maryland, Virginia and the District. "We want the house completely done so we can move on to something else."

Steady orders from builders have helped offset some of the losses from the drought, but many of the plants that are put in the ground now will have to be replaced fairly soon.

Following a few general guidelines can help keep plants alive.

Plants need about an inch of water a week and closer to two inches if temperatures are consistently in the high 90s, Prins says. It's best to water two to three times a week either early in the morning or in the evening. Water the roots, not the branches or leaves. If you are unsure whether a plant has the proper water, stick your finger into the ground at the outer edge of its root ball. If the ground is the consistency of baked cake, it needs water; if it's the consistency of batter, the plant is in good shape.

But, as Robert and Maggie Marchetti are learning, sometimes careful effort can't save everything. One stewartia and several foxgloves already have been replaced in the garden they planted this spring at their Great Falls home, and everyone's fingers are crossed about the heuchera.

"One stewartia is healthy and thriving, and the other decided to die," Maggie Marchetti said. "I don't know if the heat caused it or if it got too much water."

But she knows what killed the foxgloves: "I watered them every other day. It was too much for them.

"I'm not sure how to care for each and every plant," Marchetti lamented. "In spring it was so easy; they were just growing and happy. Now they're not as happy."

Staff writer Jessie Mangaliman contributed to this report.

CAPTION: Ciro Hurtado-Jimenez, left, and Mark Crombie, of Plant-A-Plant Landscaping Co., plant a replacement tree in Ashburn.

CAPTION: Mark Crombie, of Plant-A-Plant Landscaping Co., inspects the ground around a newly planted tree in a subdivision in Ashburn. "It's just dust," he said.