Plan now for sweeter strawberries in '83

It's getting to that time of year when strawberries--red, ripe, and delicious--will be ready for picking in the garden. At least we hope they will be delicious--as rewarding on the tongue as they are appealing to the eye.

That's not always the case, and the fault is more likely to be ours than the berry's.

Unlike most other fruits which can ripen and sweeten up after picking, the strawberry has all the flavor and sweetness it will ever have the moment you pick it. Sure, it will redden up like a rose, but its beauty will be, quite literally, skin deep.

The need, then, is to exercise a little patience and not pick the berry until it is red all over except, perhaps, for a small whitish spot where the berry rests upon the ground. After all, you can get all the sour strawberries you need from restaurants--the type you have to ladle sugar over just to make them palatable.

Meanwhile, go to your garden calendar and mark Aug. 20, or thereabouts, with a big red ''S.'' What you do during the weeks of late August and early September will go a long way toward putting bowls of red-ripe strawberries on your table next year.

I recently spent some time with Curt Massey, president of Rayner Brothers berry farms and nursery here in Salisbury. What he told me made me wish I had been a lot more considerate of my strawberry bed late last summer.

We all know the standard advice for fruit trees: Don't feed them in late summer, or the lush, soft growth that it stimulates will perish in the winter. Well, exactly the opposite applies to strawberries.

A late-summer feeding actually increases winter hardiness and can dramatically increase the number and size of the berries the following June.

This is what happens:

The strawberry plant, having spent much of the summer sending out runners, finally starts looking to its own interests and begins storing up energy that will be converted into flowers and fruit the next year. The more energy, or food reserves, it packs in, the more the plant is able to withstand the rigors of winter.

The plant stores this energy in the crown. Once it has taken in as much as it can for one crown, an interesting thing starts to happen. The crown begins forming tiny subsidiary, or branch, crowns that can store still more energy. These subsidiary crowns also send out flower stems the following year.

It follows, then, that the more subsidiary crowns a strawberry plant has, the more productive it will be.

An excellent organic plant food for strawberries, according to Massey, is cottonseed meal. Ground cottonseed usually contains 6 percent nitrogen, 3 percent phosphoric acid, and 2 percent potash. Applying it in August--four pounds for every 25 square feet--not only meets the food needs of the plants, but also adds to the organic content of the soil as it decays.

Another option is to spread weathered horse manure between the plants up to an inch thick, or to use a combination of the two.

One of the most common mistakes a home gardener makes is not renewing the bed after each harvest. Once the harvest is over, says Massey, ''mow off the old leaves, but be sure to set the mower high enough so that it will not damage the crowns.'' Now thin out the bed with a rake or hoe, leaving 4 to 6 inches between the plants.

A light scattering of soil over the bed at this stage is also helpful because it stimulates new rooting around the old crowns. Water well.

In late August apply the fertilizer and be sure to see that the plants are well watered if rain doesn't fall regularly. At this stage you are, in effect, stocking the freezer with next year's berries.

In the North a mulch should cover the plants to protect them from the deep freezes of winter. Apply hay or straw to a depth of 4 inches once the temperature starts dropping into the low 20s (F.) at night. Sometimes I apply about half that thickness of shredded leaves.

In the spring, as the new leaves start to form, take the mulch off the top of the plants, leaving an inch-thick covering between them. This not only makes for comfortable, weed-free soil conditions, but it also helps keep the berries clean once they form. And, most important, it steadily adds to the organic content of the soil.

If well looked after, strawberry beds can produce significant harvests for 4 to 5 years, says Massey