INTERIOR DESIGN is going from pot to grass, and none of your jokes please: Marijuana isn't grass.

Pots as in pottery were big when the back-to-nature movement began six years ago in reaction to the proliferation of plastics. During the pottery craze it sometimes seemed that everything from pillows to planters had to be ceramic in a properly up-to-date household.

Now the new buzz-word is grass. Woodward & Lothrop, the Hecht Co. and Bloomingdale's have separate displays devoted to grass from planters to bamboo stands. With the opening of China as a new source, many baskets of forgotten form have reappeared, such as cricket baskets. Importers such as Dockside and Pier One have long urged upon Washington the Casablanca look of bamboo furniture and fans.

Bamboo, a remarkably tenacious plant that tends to take over the garden, is doing the same with interior design, and bringing along its whole family of grass relatives. This is not of the first blooming for grass. England's Brighton Pavilion and the Regency Period were full of bamboo furniture and oriental vases full of grass. In France, straw hat making was the principal reason for many towns.

In the United States, Easter once was called straw hat day, that being the first proper day to put away your felt hat. Today, in places as far apart as the Carolinas and California, basketry is becoming the new popular craft.

In time to educate us all in the subject is a show of 540 objects made of grass just opened at the Renwick Gallery of the National Collection of Fine Arts. The show was organized by Mary Hunt Kahlenberg, textile curator at the Los Angeles County Museum of Art, and installed here by Val Lewton.

Kahlenberg came to Washington last week from Indonesia, where she was photographing and researching more grass objects for a book growing out of this exhibit. She stopped long enough to discuss how it began.

"Naively. A few years ago, as textile curator, I realized how many textile techniques are the same in grass as in farbic. Lace is made almost the same, whether of grass or linen. The show orginally started out to be about baskets, but the more work I did, the more I realized how many thousands of different objects are made from grass.

"The hardest job was to get some sort of informed agreement as to just what grass is. Even the botanists argue about it. We finally agreed to use the dictionary definition":

In the widest sense, green herbage affording food for cattle or other grazing animals, especially that of plants belonging to the families Poaceae (true grasses), cyuperaceae (sedges), and Juncaceae (rushes) in which the leaves have narrow and spear-shaped blades.

"There are other plants often confused with grass. Wicker is actually made from tree branches. Rattan is a vine. Palm is related, the next closest family for instance, but it isn't a grass, though I did have an indignant letter from the Palm Society people who though it should have been included.

"Of the grasses, bamboo is the strongest, stronger than rattan and wicker. A variety called steel bamboo is even used to make bridges in some parts of the world. In Indonesia, people make tiny bamboo baskets, fill them with a few grains of rice, throw them into the boiling pot to cook and swell and then serve them as prepackaged square rice cakes."

In the Renwick show, the objects come from everywhere - Sweden to Mexico, and points east and west. None of the objects is especially old, the odlest hardly more than 150 years, because gras usually does not have a long life. But many of the works are very old in form, made today in the same way that they have been for 1,000 years or more.

In this category is the boat prow still made by the Indians of Lake Titicaca in Bolivia. The form is much the same as used in ancient Egypt and more recently by Thor Heyderdahl on one of his voyages.

Far older are the ceremonial or votive objects made since 7,000 B.C. when the corn goddess ruled the Nile. The corn dollies, as they are called, were made of the last sheafs of grain harvested, twisted into a decorative shape, with the seeds left on them, and preserved in the house over the winter as the host for the spirit of the field. Similarly, St. Bridget's Cross on Aran Island in Ireland is made of straw and hung in the barn as a protection against evil.

Doris Johnson, who grows her own grain for her craft in Luray, Kan., made a decoration for the show combining the first evening star, the traditional sign to quit work in the fields, withe Welsh border corn dolly. The custom is also observed as far north as Scandinavia and as far south as Mexico. Kahlenberg reports a revival of interest in corn dollies in England.

Particularly decorative corn dollies are made in Switzerland and Sweden. Despite the name, the shapes are just as often stars or crosses or other geometric forms. About 12 different ones are displayed in the Renwick show. Probably the largest such corn dolly is the 25-to 30-foot Shimenawa, a rope made of rich straw and hung in the doorway of the Izuma Shrine in Japan.

In the Amazon, the important mating dance that draws villagers from miles around requires a huge grass cape with a hood covering the head. "During its feathers to attract a mate," says Kahlenberg. In Taxco, Mexican, Kahlenberg bought a magnificient mask made of reed, presumably used in some great dance.

But apart from ceremony, grass is used for utilitarian costumes. In the show is a fine grass cape and hood from Japan, worn as a protection against the rain.There are also straw overshoes, again from Japan, though similar ones are worn in Scandinavia and called sleigh boots.

The collection of hats in the show is splendid, enough to start a whole hat revival. One of the most beautiful is a 1920s hat, amde in France by an unknown milliner and collected by the Los Angeles County Museum. It has straw flowers and unusual braiding. Two others were made for horseback riders, one a no-nonsense polo hat type and another with great plumes of feathers. A straw lace collar is, Kahlenberg points out, the ultimate in Victorian obsessive ornamentation.

Musical instruments were possibility first made of grass. The show includes a great number of instruments. A type of guitar from Madagascar, collected by a botanist who specializes in grass, is highly decorated with figures showing the Dutch influence.

Like the cricket cage of China, the bamboo bird cage of Mexico has become a familiar decorative piece in American households. The one shown here is made of a small neat bamboo.

A food cover from Thailand is very finely made of intricate braiding techniques and subtly colored. A food tray from Ethiopia of dyed grass shows one example of the wide use of grass to make food servers. Another display is of food preparation tools made of grass, from tea twirlers to tongs. For modern tasts, the double basket made by the Japanese master Chikuensai Azuma may be the most beautiful object in the show.

Fans are another popular use of grass. A huge one that would have to be wielded by one's personal attendant comes from the Phillipines.

Grass furniture is not well represented in the show, perhaps because of the show's travels, but there is a chair made of grass from Adjmer, India. A slide show details its manufacture. A small stool made of rice straw comes from Japan. Rice straw sitting mats are also made in Japan and similar ones of corn husks in China. An intricately colored Chinese suitcase is one of the oldest and handsomest objects in the show. A Korean basket for flowers arrangements has a fine asymmetrical form. It was obviously made to last forever. A Polish grass chandelier surely was copied from the glass chandeliers of the gnetry, and hung on high feast days.

Grass, according to Kahlenberg, makes up a third of the plants on the earth's surface, growing from the Arctic and Antarctic to the tropics. It can be carved, cut, twined, plaited, bound, coiled, woven, spit, shredded, shaped, tied, tortured and gathered into a 1,000 shapes.

And, as you'll see in the Renwick sho, it can also be much admired.

(The show, funded by a National Endowment for the Arts grant, comes here from the Museum of Contemporary Crafts in New York, which coincidently now has the Object as Poet show from the Renwick.)