Fun among aphids and compost. LITTLE GREEN THUMBS

`IF you're interested in gardening, you'll be able to do it, no matter how old you are. ... For now, you don't need to know anything.'' With that jaunty nod of encouragement, The Victory Garden Kids Book (Houghton Mifflin, Boston, 148 pp., $12.95, age 9 and up) gets off to a rousing, child-friendly pace. In the first few pages young readers are told, ``You won't like gardening much if you can't lift the tools.'' Farther on, they find out, ``You can't be sloppy about weeds and just yank the tops off the plants.''

If those don't sound like the sorts of botanically precise instructions we may be used to hearing from the local extension-service expert, Marjorie Waters is delighted.

As author of the latest gardening book published in conjunction with public television's perennially popular ``The Victory Garden,'' she is a stickler for having fun among the aphids and compost.

``One of the things we were trying to do with this book was to see how much abuse a garden could take,'' she says, almost straight-faced. ``The answer is: It can take a lot.

``We also found, thanks to five-year-old Ben Mottau, that a chive plant can be moved 40 or 50 times and still survive.'' Energetic Ben was one of seven youngsters, aged 3 to 13, who spent the summer of 1986 planting seedlings and battling Japanese beetles in a suburban backyard garden with the help of Ms. Waters and photographer/father Gary Mottau.

It was a first for the kids, most of whom didn't know a trowel from a poke hole. It was also a first for Waters. She'd been co-writer, with the late TV host Jim Crockett, of the three previous ``Victory Garden'' books - ``Crockett's Victory Garden,'' ``Crockett's Indoor Garden,'' and ``Crockett's Flower Garden.'' But she'd never written for children before.

The idea was to take the step-by-step approach to gardening, which had proved so successful with adult readers of the ``Victory Garden'' books, and make it accessible to youngsters. But theories needed testing, and the call went out for neighborhood kids.

As the zucchini and cauliflower sprouted, the book began to take shape. Opening chapters on ``Digging,'' ``Making Compost,'' and ``Bugs and Other Munchers'' were quickly followed by individual chapters on 30 different fruits, vegetables, and flowers, ``all easy to grow.'' The focus of the book remained the same, however, even as the weeding gave way to harvesting.

``We were more interested in kids having a wonderful time and experimenting than we were in formalized teaching,'' Waters explains.

``We wanted the book to feel kid-like, to feel like dirt.''

The seven aspiring horticulturists did, indeed, have a good time. They learned how to use their hands to span distances and dig poke holes for seeds. They cut out ``maggot mats'' to protect broccoli seedlings and generally overcame their squeamishness about bugs.

Best of all, they loved snack time: raw veggies fresh from the earth.

``The kids used to walk through the garden chewing on parsley and chomping on chives,'' Waters recalls. ``My son Sam's passion was cauliflower. He couldn't get enough of it. With dip, mind you - he's not a real purist.''

As the youngsters grew to understand that plants needed to eat routinely, just as they did, they doused cantaloupe plants with ``manure tea'' and built a sizable compost mountain. The cantaloupes, like a couple of Brussels sprout and beet seedlings, didn't make it - and that, too, was a lesson worth learning.

``Our assumption was that what happened, happened,'' Waters notes. ``We didn't use any chemical fertilizers, any insecticides, or any fungicides, because we wanted them to know that [gardening] was a natural process that didn't depend on something in a bottle.'' The result of this sweet basil summer is a book designed to be read by a novice nine- or 10-year-old gardener with the hope that his or her parents will join in and supervise the crop rotation.

``I suppose some very disciplined kids could take the book and go off and garden on their own. But what I was hoping to do was to give adults a way of sharing something with their kids - adults who garden and adults who don't garden,'' Waters says.

The one response she probably wasn't prepared for was that of her five-year-old son, Sam. ``His mother wrote the book. He's in the book. He hears it talked about a lot at home - which may explain why he has such a funny relationship with it,'' she comments.

``The thing is he likes it as a bedtime story. My husband just last night read him to sleep with [the chapter titled] `Watermelons.'''