A big flower show, the Washington International World of Plants and Flowers, began its five-day run yesterday at Capital Centre in Landover.

Once the mind recovers from the mind-boggling" 35-foot high volcano, centerpiece for the show, and which may give the gardener some ideas for installing volcanoes (where appropriate) in his own garden, the visitor can explore the 2-acre show. And yet, if one has no room for a volcano or a 70-foot "tarzan vine," and in fact has nothing more than five ailing begonias trying to get through the winter, there is a University of Maryland Extension Service booth called the Plant Information Center, prepared to advise on almost anything.

There is a 14-foot waterfall, plus a lagoon full of water lilies in bloom and bright fishes (it cost $12,000 in case you think it would be grand near the garage).

A good section is being devoted to "arrangements" of flowers, with some attention given to dried flowers, and an exhibit of terrariums, fiber glass ploors (you just dig a hole and set them in, and you're all set) and a little group of flowering cherries in bloom.

A 2,400-square-foot jungle has been created with such notables as a 40-foot Norfolk Island pine in it, and a pair of 24-foot double-trunked ponytail palms. Golden spider monkeys in bamboo cages add a further dimension of simian chatter to the show and, though they add nothing to music, a collection of land crabs.

There are some 10-foot-high carved wooden tiki idols and six stone pools. People who provide golf courses with grass have a putting green, and give advice on grass.

Six greenhouses have been erected for temptation's sake, and there will be an exhibit of hydroponic (water, not soil, is the growing medium) gardening.

The Virginia Polytechnic Institute, so very sound on grapes, among many other things, will have staffers along with the District's own. Extenstion Service to offer free soil analysis, and some hanging baskets of vegetables with apartment dwellers in mind.

A wine garden and a beer garden are displayed, and among the 100 commercial displays are some devoted to such practical things as fences.

The National Arboretum, and Maryland's forestry department are represented, along with the Maryland Horticultural Society, Brookside Gardens (the splendid public gardens at Wheaton) and the Department of the Interior which demonstrates its system of seasonal changing of flowers in parks.

The volcano, which cost somewhat less than $10,000 - a bargain the more you think of it - has a frame of chicken wire, ladders and black plastic sheathed with 28,000 pounds of red rock from Colorado.

Show hours are noon to 10 p.m. today and Saturday; 11 a.m. to 10 p.m. Friday and noon to 8 p.m. Sunday.