GARDENING : FRAGRANT, TOLERANT ELAEAGNUS MAKES ITS OWN FERTILIZER.

Byline: Joshua Siskin

Imagine a plant that produces fragrant flowers and edible fruit, grows in sun or shade, tolerates heat, wind and ocean spray, requires a scant amount of water and never needs to be fertilized. As if this were not enough of a resume, it also makes a fine hedge and may be kept at any height between 4 and 15 feet.

The plant in question is the Elaeagnus pungens, commonly known as silverberry or thorny elaeagnus. This is the time of year when it flowers and purveys its pungent perfume to passers-by.

If you are unfamiliar with the thorny Elaeagnus, you may walk right by it, wondering at the mysterious source of the delightful scent that bewitches your nostrils. The species is not remarkable for its beauty, its leaves a drab olive green on their upper side and tan below. There are brown dots all over the leaves, giving the plant a sickly look that is without justification since it is inordinately resistant to diseases and insect pests; these dots are merely part of the leaves' natural pigmentation.

Elaeagnus pungens is sort of the Abraham Lincoln of the botanical world. Its outstanding character traits impart to its homely appearance an air of inexplicable dignity.

One of the most fascinating aspects of Elaeagnus is its physiology. It lives in symbiosis with soil bacteria that form nodules in its roots. These so-called nitrogen-fixing bacteria take nitrogen out of the air and combine it with oxygen to form nitrate - the same nitrate that is found in most store-bought fertilizers. In return for the nitrate they provide, these root-dwelling bacteria receive carbohydrate manufactured in Elaeagnus leaves that is transported down the length of the plant. This kind of symbiosis, incidentally, is also found in leguminous or pod-forming plants - including peas and beans, wisteria vines, acacia, mesquite and coral trees. Plants that live in symbiosis with nitrogen-fixing bacteria do not require fertilization and are used throughout the world in infertile, nitrogen-poor soils as sources of food and fuel. Self-fertilizing acacia trees are used for reforestation of ecologically ravaged areas in South America, Africa and Asia.

Because Elaeagnus promotes the growth of nitrogen-fixing bacteria, it makes an outstanding companion plant in the garden, landscape or orchard. The plants that grow around it will have their fertilizer needs reduced and be more productive. Elaeagnus may significantly improve yields from nitrogen-greedy plum and nut trees, for example, when it is interplanted among them.

Do not prune elaeagnus between the time it begins to flower, in the fall and the spring. Pruning during this period will remove the developing berrylike fruits. Both the fruits and the seeds of Elaeagnus are edible. Before consuming seeds, however, you will want to remove their fibrous covers. Elaeagnus makes an excellent container plant. It will waft its fragrance over your patio or balcony each fall, requiring a minimum of maintenance the rest of the year.

Tip of the week: A famous fragrant plant that blooms in October and November is night-blooming jasmine (Chestrum nocturnum). In the Valley, plant it in partial sun or light shade to protect it from summer's scorch. This plant's strong fragrance, which is only produced at night, even though its flowers open during the day, is so intense that some people find it offensive, if not intolerable.