Invariably, my garden plan, by May, is scrunched up in the back pocket of my overalls, having gone through the wash more than once and been rendered illegible. Probably just as well. Someone once said the problem with making plans is they might come through. That doesn't mean you shouldn't have good intentions about laying out your garden. Besides, it's a lot of fun when it's cold, picturing how the tomatoes go here, the lettuce there, the zucchini over by the fence, the peas up the trellis, which will go over here . . . USE GRAPH PAPER: Available at office supply stores and art stores, graph paper is useful because you can easily draw your garden to scale. If you're like me and plant your vegetables in blocks, graph paper is practically a necessity in planning your garden. If you plant in rows, however, you could probably get away with using a legal pad. PLAN PATHS: Such a small detail, and one that's really easy to overlook, but accommodating paths in a garden map is important. Better to have a smaller patch or row of bush beans than not be able to get to them when they must be picked. If you have a vegetable garden that's large enough for a path down the middle, for heaven's sake make sure the path is wide enough to get your garden cart or wheelbarrow all the way down to the end. In the middle of the summer, when the ground is drying and the weeds are getting high, you'll undoubtedly decide it's time for another application of mulch -- several cart loads. And if your garden is big, you'll need the cart to haul vegetables out during harvest. SPACE PLANTS: If you use cages for your tomatoes, allow enough space between the cages not only for you to walk all the way around them, but also at least an extra foot to accommodate foliage and vines that will push through the cage and drape themselves willy-nilly outside. Otherwise, one ends up, in August, literally crawling between cages to pick the fruit because the tomatoes have grown together in one huge matted mess. CONSIDER YOUR SOIL: If you have very rich loamy soil, you can crowd certain vegetables, such as lettuce, spinach, beans, peas, even root crops like turnips and carrots. Don't try to squeeze a dozen broccoli plants into a two-by-three-foot patch. Don't crowd cabbage, Brussels sprouts or corn. These vegetables need space to produce well. If your soil is average, follow space recommendations on the seed packets. SPACE SAVERS: No matter how large the garden is, there's never enough space for all the things you want. But many new varieties of vegetables are bred for compactness. There are a number of good bush-type squashes, like cantaloupes, cucumbers and even summer squashes, that, while they may be a little less prolific, won't take up nearly as much space as the viney types. TRELLISES: Trellises save space and give shade for cool-weather crops such as lettuce and spinach. I don't bother with bush beans or bush peas, growing the pole varieties instead, which give larger harvests in less space. All my cucumbers and many vining squashes are grown on trellises, although you have to be careful with the squash family: too much handling, though it may be necessary when training vines onto a trellis, can bring on wilt disease. FOLIAGE FANTASY: One of the largest greenhouses in the metro area, Seneca Falls Greenhouses, Routes 7 and 606 in Vienna (six miles west of Tysons), is having an interesting show beginning Saturday and running through February 14. The greenhouse is big in bonsai, and for this show, owner Julie Graham has brought in a lively selection of orchids and African violet