Seed catalogues this year are featuring more and more new strains of "patio" plants - vegetables, flowers, bushes, even trees - developed to be grown in pots and tubes. For just a few pennies, they suggest, you can have your own Eden and grow more deliciously fresh vegetables than your family can eat.

Pennies for the seeds, sure, but wait 'til you start pricing pots and tubs!

Even plastic ones are prohibitative, and who wants them? The price tags on pottery and wooden planting receptacles will start even the all-thumbs carpenter thinking do-it-yourself. Which is fine, except you've got to remember that you're bullding something to contain dirt, wet dirt, so materials reasonably rot and rust-proof are essential.

Alluminium is ideal, but it's expensive and working with it requires tools not found in the average homeowner's chest. Most people wind up with redwood, the suggestion you'll get at the lumber yard.

Fine, but redwood also puts a dent in the pocketbook and it's tricky to work with - it splits easily and isn't very strong . If a redwood tub isn't properly cross-grain braced, it's not going to last.

The best bet is a trip into the country to a sawmill, which is fascinating place to visit anyway. Oak is what you want, rough-sawn green oak. If you treat it right it will last as long as redwood, and it's a lot easier to work with. And, unless the sawmill operator spots you as a city slicker, a $10 bill will get you enough for three big tubs. If he asks more than 25 cents a board foot, argue.

The easiest oak planter is probably an 18" cube with no top. Your need a 1"x12"x8' and a 1"x6"x8'. Saw each into three 18" peices and two 16" pieces. Rip the leftover piece of the 12" board into four equal strips. (Remember that with rough lumber you've got true measures - a one-inch board is one inch thick.)

The only other materials you'll need are 241 3/4" aluminium screws.If you have corner clamps, the assembly is a breeze. Clamp two of the 18" and the two 16" pieces of the 12" board into a box. Select a drill bit the same gauge as the screws and mark it with a masking tape 1 1/4 inches from the tip. Hold one of the strips of the scrap in a corner so about half of it is above the box and drill through each board into the strip up to your mark. Insert a screw in each hole and drive it in with a hammer until 1/4 inch protrudes. Tighten with a screwdriver.

Complete the box of the 12" boards, then follow suit with the 6" boards atop it, putting the 18" pieces over the 16" ones and vice versa. Use the same drilling and hammering procedure with the other eitht screws to attach the remaining 18" pieces as the bottom.

Variations on this basic tub are limited only by your craftsmanship and imagination. Using all 6" boards with the side pieces vertical is a simple one. Or skewing the sides by ripping pieces corner to corner, using a framing (rafter) square for precise end cuts, and alternating these pieces with plain boards.

Another method is lacing an oak tub together with nylon cord. Simply be sure you get the non-stretch kind of cord, not that used for porch furniture. For decorative effect, mix in some planks from slabs - the outside planks from a log, with the bark. Just remember that they've not as strong.

Use your oak planter the first season just as is. Empty it and let it dry out throughly the next winter and give it a good, soaking coat or two of creosote. Repeat each year and it might outlast you.