The National Arboretum has ventured briefly into Georgetown with a modest display of Chinese garden plants in the Georgetown Park shopping mall on M Street.

"We're in pothole heaven out here," said Henry M. Cathey, director of the National Arboretum in northeastern Washington, "and thought it might be nice to try uptown."

So a modest planter box or two of standard and good Chinese plants have been installed on the tile floor of the shopping mall, a display 20 by 20 feet with a nice quatrefoil gate suggesting a moon gate.

"You can say what you like about the Chinese juniper," Cathey went on, "but at least it gets through the winter." (The Chinese juniper, in a number of varieties, is, like the native red cedar juniper, an aristocrat among conifers.)

Cathey is a bit touchy at the moment, since the arboretum's 900 camellias, superbly sited on a wooded slope, were decimated by the recent winter and only 27 came through in satisfactory condition. Hence, the director is quite hot for plants that will make it in Anchorage.

Of the plants displayed, now through the next three weeks, two are certain to be killed even in ordinary Washington winters (the dwarf running gardenia and Ardisia crenata) while two others (Mahonia bealeii and Nandina domestica) were severely damaged this past winter, though usually considered bone-hardy.

Others, such as Euonymus alata, Cotoneaster dammeri, Phyllostachys aurea, Liriope (according to the label) variegata, Berberis julianae, the Hangkow and Babylon willows, the Harland box, golden Pfitzer juaniper and pink flowering almond and blue Chinese wisteria, are hardy even in subzero winters.

The little exhibit of plants--modest specimens of all of them--serve two purposes: they remind citizens there IS an arboretum, and they hint what is perfectly true, that China is the world's preeminent fountain of gushing delights for the American garden, since (not to split hairs) virtually everything worth growing is Chinese.

The leatherleaf viburnum, V. rhytidophyllum, is included, possibly as an example of the only fairly ugly species of a magnificent genus.

Cathey himself, who is one of the nation's knowledgeable and most entertaining speakers on gardening, will be present from 2 to 4 p.m. Sunday at the exhibit to interpret it, and will speak of it on WRC radio from 9 to l0 a.m. Sunday.

There are four quite beautiful Chinese carved stone dogs guarding the plants, whose labels are in English, Latin and Chinese (thanks to the chef of a Chinese restaurant near the arboretum).

"If it speaks Chinese," said Cathey, possibly thinking of his ruined Japanese camellias, "you have a better chance."