That bag of grass seed or lawn food tells you a lot about proper care

All you need to do is learn what the printing on the bag means.

If a homeowner wants a lush green lawn, he cannot go too far wrong if he buys from a company that will refund his money.

Does the bag state plainly that the company will mail you a check at once if you simply say you're not satisfied with the product? No questions asked? No hassle? Just some reasonable proof of purchase, such as the sales slip.

A lawn-food bag should give you six facts:

* The recommended method of seeding, fertilizing, watering, and defeating weeds.

* Explicit directions for applying what you are buying. If you use a spreader , for example, then what is the specific setting?

* How big an area you can count on covering.

* Any toll-free (800) telephone number you can dial for guidance from experts , research specialists, and practical lawn consultants.

* Any exclusive or patented feature to justify a higher price.

* A guaranteedm formula. In a bag of grass fertilizer, it might be 34-4-4 or 27-3-3, while in a sack of grass seed, it might be a blend of bluegrass, fine fescue, ryegrass, etc.

So far as I'm concerned, I don't get mired down in the ''numbers game'' of the fertilizer trade. Those number codes that signify so much nitrogen, so much phosphate, and so much potassium can easily mislead.

Consider N, the standard symbol for the nitrogen your lawn needs. This substance can come from several sources. A supplier of sacked grass fertilizer sometimes uses twom sources -- urea and ureaform -- to provide nitrogen.

The first, urea, will start to release its nitrogen about three days after application and will finish up in about three weeks. The ureaform, however, doesn't even begin to break up until six weeks after application; then it continues releasing for perhaps three months.

Between the end of one release and the start of the other, there is a hiatus. What you get is a kind of roller-coaster effect. First a feast, then a fast. Finally, long, slow fertilizing.

Some fertilizer companies compromise on their chemical formulas. In other words, they draw on nitrogen sources meant for something else and adaptm them for lawn use. They simply mix in a little phosphate and potash; then voila,m they have their turf fertilizer. It's good, of course, but not good enough for the lawn.

Instead of any such mix, you'll do better selecting a uniform and homogeneous product. When you pick up a handful of it, examine it closely. Do you see the separate particles of the nitrogen sources? Do they differ in color and size? That will warn you that the package contains a physical mix, not a composite blend.

What you should see are tiny, look-alike, same-size balls, each of which contains within itself all three fertilizer fractions: nitrogen, phosphate, and potassium; in other words, a completem fertilizer.

One trouble with a mix, even at a bargain price, is this: The heaviest particles (nitrogen) settle to the bottom of the paper bag. When you pour them into the bin of your spreader, they go out last and may burn patches or streaks in your lawn.

(Incidentally, you shouldn't have to ''water in'' fertilizer when you spread it on the lawn.)

After you have emptied a bag into a spreader, it's a good idea to cut out the face of the bag, which then becomes evidence of purchase should you want to claim a refund.

The best time to rebuild and revitalize your lawn?

There isn't any badm time. Immediate growth is faster in the springtime, but fall feeding works during cold weather to build root systems. Grass plants will respond to a year-round diet, if the menu is right.

Should the foregoing shatter any innocent assumption on anybody's part that lawn-raising is simple, let him (or her) learn from those who study the care and feeding of grass. Seed farmers and fertilizer manufacturers maintain experimental plantations - acre upon acre of test plots. Comparisons among grasses and among methods of feeding and watering them go on continually.

These producers bear in mind that your lush lawn, intelligently cared for, will go on greening for 20 years or more. Their goal is to enable you to invest knowledgeably in your own property.

Thus, it is not merely the bagged fertilizer or herbicide or formulated seed they provide, but also the newest and soundest methods of applying such products. The manufacturers tell you, right on the bag, exactly what spreader setting to use to spread lawn products evenly, in the correct amounts, and without overlapping.

Lawn products are just too valuable to waste by broadcasting them.

Today, too, you can buy lawnmaking materials exactly according to the size of the area to which you are going to apply them.

Above all else, pay a little more for your lawn products and you're likely to get a lot more for your money.

Formula is more valuable to you than low price.