Saltwater plants are useful for growers who are attempting to grow plants close to the coastline. Whether you plan to grow these plants in a saltwater pond or in soil watered by high-salinity water, these plants will provide an interesting and unusual addition to your garden or yard. Saltwater plants vary widely in their environmental requirements. Some, like kelp and other forms of seaweed, are aquatic and grow underwater. Others, such as the mangrove tree, are terrestrial and have a tolerance of or need for salty water or soil. The requirements for growing such plants differ widely for terrestrial versus aquatic types.
Determine what kind of saltwater plant you want to grow. There are two primary categories to choose from among plants adapted to saltwater. The first is a group of plants called halophytes, which are terrestrial plants that can tolerate -- and in some cases require -- salt to be present in the water they take in. The second category is aquatic plants that grow in saltwater and includes seaweeds and similar plants. Choose from the first category if you are planting on soil watered with saltwater and the second if you intend to populate a saltwater pool with aquatic plants.
Determine the salinity (in other words, salt concentration) of the water you will be using for the plant. This step is most important if you are growing halophytes, which differ widely in their range of salinity tolerance. You can do this relatively easily with an electrical conductivity meter. These devices are relatively inexpensive and available from vendors that sell equipment to farmers. Follow the instructions provided by the manufacturer of the instrument.
Choose a plant from the category you have selected with the appropriate salinity tolerance. Halophytes, especially, vary widely in their tolerance of salinity. If you will grow the plant outdoors, research what types of plants are most suitable for your climate and region.
Plant the halophyte or aquatic plant according to its individual needs. Planting requirements differ widely based on the species of plant you want to grow.
Care for the plant as needed. Seaweed generally requires little maintenance, but halophytes can require a lot care depending on the species. Avoid changing the salinity of the water you use with these plants.