You have a problem in your yard or garden. Maybe the water cuts a muddy swale through the grass of a hillside every time it rains, or everything you plant in a particular location dies, or you live near a stream where erosion is undercutting the banks, or your plantings just aren't doing what you intended.

You know you need help, but where do you go for advice? Do you need a landscape designer, a nurseryman, a groundskeeper, an engineer or excavator? Do you need work that involves a shovel, or will a bulldozer be required? Will you be at the mercy of the person you hire or have some input in the process?

Following is a primer on experts, the different types of professionals with whom you are most likely to come into contact while you consider beautification, transformation and maintenance of your property. It will help you figure out what people in a particular specialty do and what you can expect from them. One thing I believe you can expect from all of them is that you will be included in the creative work. It's your property, and most professionals are eager to make it work for you.

In general, contractors who belong to professional organizations have pledged to meet certain standards and to perform in a professional manner. These organizations set standards, oversee licensing and registration, and certify professionals. However, the best recommendation for any person or company you're thinking of hiring is references from satisfied customers. Ask for references and proof of insurance.

* Landscape architect. A landscape architect oversees the landscape design of large-scale projects, such as the regional planning of parks, subdivisions, apartments and other commercial sites. Landscape architects also perform residential landscape design. They do landscape construction design and develop planting and drainage plans. Their education gives them an understanding of plants and sensitivity for the environment. Landscape architects must pass the strictest licensing requirements of all landscape professionals, and their practice is regulated in about 40 states.

For information about where to locate a Registered Landscape Architect and how to learn more about this profession, contact the American Society of Landscape Architects, 636 I St. NW, Washington, D.C. 20001; call 202-898-2444 or 888-999-2752; Web site: www.asla.org.

* Landscape designer. Through education, training and experience, landscape designers engage in the consultation, planning, design and construction of exterior spaces. Their designs locate plants and the incidental paving and building materials necessary to enhance a property, such as trellises, water gardens, paths, patios, walls, arbors, sculpture, furniture and the like.

Landscape designers might have a certificate, a bachelor's or a master's degree in a landscape design curriculum. Training is usually in horticulture. But individuals using the title "landscape designer" are not required to have training in the profession. One way to know a landscape designer's expertise and experience is through a nationally recognized certification program offered by the Association of Professional Landscape Designers. Ask whether the designer is a Certified Professional Landscape Designer and a member of the association. And of course, ask to see examples of work and references.

Information about finding a Certified Professional Landscape Designer is available from the Association of Professional Landscape Designers, International Headquarters, 1924 N. Second St., Harrisburg, Pa. 17102; call 717-238-9780; Web site: www.apld.org.

* Grower or nurseryman. These professionals represent the source of your plant material and are often employed at nurseries, garden centers or large general landscape companies. They also know about growing and site preparation. Many garden centers offer a full line of products and services for do-it-yourselfers.

For names of nurseries, garden centers and landscape companies that offer design, installation and care, contact the American Nursery & Landscape Association, 1000 Vermont Ave. NW, Suite 300, Washington, D.C. 20005; call 202-789-2900; Web site: www.anla.org.

* Grounds manager. The importance of home lawns and golf courses has catapulted these pros to the forefront of the greens industry. Grounds management includes pruning, fertilizing, mowing, pesticide application, seeding, weeding, mulching, snow removal and more. Grounds managers know general cultural practices for plants as well as how to operate and repair landscape equipment.

Professional grounds managers are employed to care for trees, shrubs, flowers and lawns. Ways to certify expertise in this field are through the Professional Grounds Management Society or by investigating a firm's qualifications yourself.

The society can give you names of Certified Grounds Managers and Certified Grounds Keepers. To locate certified grounds professionals, contact the Professional Grounds Management Society, 720 Light St., Baltimore, Md. 21230; call 800-609-7467; Web site: www.pgms.org.

* Landscape contractor. Contractors are the professionals who install the grounds design. But, as with general contractors associated with nurseries or garden centers, they oversee a wide range of projects from landscape architecture and design to grounds management. They have a variety of experience and expertise. Check their work and references, especially if you're hiring one to oversee a project from beginning to end.

For more information, contact the Professional Landcare Network, 950 Herndon Pkwy., Suite 450, Herndon, Va. 20170; call 703-736-9666; Web site: www.landcarenetwork.org.

Time to Subcontract

There are some types of contractors you might need to work on your property, but you will not necessarily be hiring them yourself. Some homeowners might not be able to tell an excavator how to rearrange vast quantities of soil in the landscape, or explain to an engineer what is needed to shore up a sagging patio. In these situations, these people are often hired as subcontractors by the professional landscaper, designer or maintenance professional with whom you're working. These pros include:

* Masonry contractors. Masonry includes brick, stone, marble, terrazzo, tile, plaster and cement, concrete and concrete block. These professionals will create or repair steps, porches, sidewalks, chimneys, walls or built-in barbecues. They can repair or re-point brick or stone, and install or repair concrete block. A professional organization representing these professionals is the International Masonry Institute, 42 East St., Annapolis, Md. 21401; call 410-280-1305; Web site: www.imiweb.org.

* Excavators. Excavators work with large loaders and graders to prepare a site and move large quantities of soil. They usually work with general contractors who have some knowledge of earth-moving requirements. You or your contractor should ask the excavator for references and proof of insurance.

* Engineers. A contractor might also need to hire a civil or professional engineer to determine certain structural requirements of a project. If you're building a roof deck and garden, an engineer could assess the existing structure to determine how much load-bearing capacity it has, and how the structure might need to be reinforced or altered to withstand the weight of the new construction. For more information contact the National Society of Professional Engineers, 1420 King St., Alexandria, Va. 22314; call 703-684-2800; Web site: www.nspe.org.

Finally, there is the Agriculture Department's Cooperative State Research, Education and Extension Service. These horticultural experts, found in nearly every county in the United States, range from trained master gardeners to PhDs dedicated to providing thorough, unbiased information about every aspect of landscaping. Whatever you need to know, they'll get you the answer. It's an invaluable service for do-it-yourselfers. To find the extension office near you, go to the Web site at www.csrees.usda.gov and click on Local Extension Offices.

Joel M. Lerner is president of Environmental Design in Capitol View Park, Md. E-mail or contact him through his Web site, www.gardenlerner.com.