If you have a chain saw, some oak trees you can spare, and a couple of years for the venture, you can grow your own shiitake mushrooms.

Hiroatsu Sato of White Hall, Va., who began growing shiitake mushrooms on a small scale in 1978, expects to harvest several thousand pounds this autumn. Sato is a financial consultant for Innisfree Village, a residential community for handicapped people, and he says that the steady, simple, methodical tasks required to grow shiitake mushrooms can easily be performed by Innisfree villagers. His house is tucked among black walnut and chestnut oak trees along with low, neatly criss-crossed piles of logs impregnated with the spore of shiitake mushrooms.

Sato learned how to grow mushrooms in his native Japan by working with a mushroom farmers co-op in the early 1960s. "The co-op people said we should take some injected logs home, so we did, in the spring," says Sato. "We lived in Tokyo, right in the city, but we left that log in the yard and grew our own mushrooms."

The Virginia countryside presented a more promising mushroom-growing environment than downtown Tokyo, and Sato's success provides a good model for many a backyard mushroom grower. Step by step, to grow shiitakes:

1. In winter or early spring, cut down a living oak tree, preferably 20-40 years old or 10-15 inches in diameter. Let it sit two weeks before cutting it into logs.

2. Cut all branches with diameters of 2 1/2-6 inches into 3- to 5-foot lengths (the shorter they are, the easier to handle).

3. Drill holes 1/2 inch wide by 3/4 inch deep, just to the depth where the bark meets wood. Drill holes six inches apart, spiraling around the log. A 6-inch diameter, 3-foot long log will have at least a dozen holes.

4. In early April, inoculate the log by placing mushroom spawn in the holes and tamping or capping tightly.

5. Stack the logs in 10 layers of 10 parallel logs each, with alternating layers perpendicular to each other, in a moderately shady location for one month.

6. Restack the logs similarly but with five logs in each of the 10 layers to allow more air space between them, also in a moderately shady location, through the summer.

7.In the fall, remove the logs from stacks and rest one end on the ground and the other end on a support log. Do not stack one upon another.

8. Throughout fall and winter, turn the logs one half turn so the bottom comes on top and flip them end to end so the other end touches ground. If the spring or summer season is particularly dry, occasional sprinkling will encourage fungal growth.

9. In autumn, tiny buttons can be seen to emerge. Once they are visible, stand the logs up straighter, against trees or sawhorses. Maintain moisture if necessary by sprinkling.

Sato says he and the Innisfree villagers will harvest more than 5,000 pounds of mushrooms this year. He plans to sell them to restaurants and individuals in the Charlottesville area. Now that he has entered the commercial mushroom market (even if not on the scale of the Elix Corp. 50 miles south), he maintains some control as sprouting season approaches by dipping the logs in a large vat of water, covering them with a plastic tarp, and resting them on a basement rack as the mushrooms become ripe.

But Sato and other experienced mushroom growers agree--even if all you do is cut up an oak tree, inoculate a few branches and leave them in a shady spot, you should see a few shiitake mushrooms sprouting in approximately 18 months. The more maintenance you give the logs, the larger your harvest will be.

Mushroom spores and growing instructions are available from Elix Corp. (Route 1, Arvonia, Va. 23004) and Dr. Yoo Farm (P.O. Box 290, College Park, Md. 20740).

Elix Corp. supplies one bottle of mushroom spores, enough to inoculate 20 to 30 four-foot logs, for $21.50 and will also supply 500 waterproof plastic plugs for $3 (enough for 20 to 30 logs in holes drilled by standard 5/8-inch bit).

Byong W. Yoo, who has been growing shiitake mushrooms since 1974, supplies 500 shiitake spawn chips (enough to produce 250 pounds of mushrooms in the next 5-6 years), spore-impregnated wood-chip plugs and matching drill bit, for $26.50.