MISSISSIPPI STATE -- Knowing that proper landscaping can add as much as 15 percent to a house's value makes it easier to avoid the temptation to hire someone to do the work just because they are cheap.

Patricia Knight, assistant horticulturist with the South Mississippi Research and Experiment Station in Poplarville, said landscaping takes time to learn and do correctly. Hiring someone to do landscaping without knowing their credentials or references can be a big mistake.

"It's risky to hire somebody off the street who has no references and you have no way to get hold of them. What happens three months down the road if they over-fertilized or you have some type of problem with your landscaping?" Knight asked.

Established businesses have a vested interest in keeping their customers happy. They offer continuity of services and are able to respond whenever something happens with a landscape.

"The thing professionals need, whether they have a college degree or not, is a good working knowledge of horticulture," Knight said. This includes planting and maintenance practices, insect and disease control, turf grass, irrigation, flower beds and more.

Knight recommended checking the references of a landscape professional before hiring them to do work.

"It is essential to know what kind of work they have done in the past," she said.

Norman Winter, Mississippi State University extension horticulturist, said another reason to hire professionals is to ensure the plants installed in the landscape are well-cared for and disease- and insect-free.

"You don't know the history of the plants if a person just shows up at the door," Winter said.

If someone comes offering to do landscaping, ask to see credentials, Winter said. Professionals have certain affiliations and accreditations and don't mind giving proof of their position.

Installing and maintaining a good landscape is a long and somewhat expensive process, but worth the investment, Winter said. Not only does an established landscape add to a home's value, but it also can cut heating and cooling costs.

Winter cautioned that if a landscape plan requires structural improvements, such as a retaining wall, irrigation or support, a professional should be used.

"By all means, you need a professional to do the work rather than a fly-by-night," he said.

Nurseries and garden centers usually have at least one trained and certified designer, architect or nurseryman on hand to assist customers. These people can be hired to do the work or can teach customers what to do.

"It is a big cost, but it will pay off in the long run to install a landscape that will perform well over time," Knight said. "Plants are not a short-term investment, and it may take several years for a landscape to look established. Having an instant landscape may not be the best thing for the yard or the home."