Any gardener living near the seashore has a tremendous treasure chest of free fertilizer merely for the taking—seaweed. Not only does it contain the trace elements necessary for normal plant growth, but also it is a valuable source of the major fertilizer elements.
Any seaweeds that wash up on the beach in quantity can be gathered and used for fertilizer.
On Florida’s east coast, the most abundant are two species of gulfweed—Sargassum natans and S. fluitans. These are recognized by their light to dark brown color and berry-like floats.
Another seaweed that may be used is Digenea simplex—a coarse and bristly plant, dark red to red-brown in color. The branches are heavily covered with slender, stiff hairs.
Large quantities of seaweed wash up on the beaches during and after storms and other unpredictable times of the year.
On the east coast of Florida, large piles several feet deep are sometimes found adjacent to the windward side of breakwaters. At times, great quantities can be collected.
Seaweed contains a mass of nourishment. A great deal of rich soil is being washed into the ocean all the time.
Marine plants can pick up and concentrate hundreds of times more plant food elements that are dissolved in the sea around them.
First Step After Gathering Seaweed
The first step after gathering seaweed is to wash the salt out of it with fresh water. This is a precautionary measure; sometimes, there is little or no salt accumulation on the seaweed, and at other times there may be a great deal.
However, there are plants quite sensitive to even a trace of salt. Therefore, after washing, the seaweed is ready for the compost heap.
Seaweed can even be applied directly to the soil around trees, shrubs, and flowers.
Composting Seaweed
A very successful way for the home gardener to compost seaweed is to mix it with soil in a flat hole about a foot or so deep.
No additional fertilizer is needed—in fact, it may be harmful. Vegetables grown in this seaweed composted soil are high in nutrients and grow very vigorously.
Seaweed has many advantages as a mulch. It not only holds moisture but also decays, adding valuable minerals and reducing the pH of the soil.
Fairchild Tropical Garden, one of Florida’s famous tourist attractions, reports it keeps a seaweed compost pile. Seaweed compost seems well adapted for the needs of many tropical plants.
Bugbear Seaweed
Seaweed is a bugbear on bathing beaches and is promptly removed, so quick gathering on the gardener’s part is often necessary. Unfortunately, seaweed decomposes slowly and has an unpleasant odor.
One plan to keep your neighbors from complaining is to cover the seaweed with a layer of sand or soil and keep it moist. This will speed up decomposition and also trap odors.
A preliminary chopping of the fresh seaweed into fairly small particles makes it possible to work it into the soil or cover it with a much thinner layer of soil.
The preliminary removal of shells, sand, and mud, as well as salt, adds considerably to the value of seaweed as a fertilizer. Hand stirring in a large open tank is one way of doing this successfully.
Seaweed Fertilizer
Because of seaweed’s ability to reduce alkalinity is especially valuable to trees and shrubs requiring acidic soil.
In Florida, these include lime, avocado, and mango. A mulch is 1 1/2 inches deep, extending from within 6″ inches of the trunk out beyond the drip is recommended.
A florist here with a grove of coconut trees finds seaweed, which helps his trees bear larger and better fruit.
The Marine Laboratory of the University of Florida has done considerable research on seaweed. It reports that seaweed fertilizer is superior to many chemical fertilizers because its high proportion of organic matter aids in retaining water and minerals in the upper levels of the soil where plant roots can absorb them.
Another advantage of seaweed fertilizers is their lack of the undesirable seeds and fungus spores in manure.
44659 by Anne G. Whitaker