Atmosphere: Carry-out casual. Price range: Sandwiches and salads up to $2.50. Hours: 8 a.m. to 6 p.m. Monday through Friday. Reservations: Not necessary. Special facilities: Accessible to the handicapped. Credit cards: None accepted.

A friend asked me not to write about Grass Roots' - it already is too crowded, she says, when she goes to lunch there. But I was unable to resist, for the surroundings (summery), as well as the food (natural) are too good to keep to myself.

The only thing wrong with Grass Roots is its hours - 8 a.m. to 6 p.m. Monday through Friday - which means lunch or a very early dinner. I decided on dinner one evening when my husband worked late and my two-year-old was in no mood to wait out my preparations.

That night it was below freezing and the wind stung our faces as we pushed through the doors of the Atrium Building. Inside was an oasis from winter. Banks of lush green plants and trees were everywhere.

In the back of the courtyard is Grass Roots, really a garden within a garden. The decor is pure summer: A few bright green-and-glass pation tables line one wall which is papered in a leafy green pattern; the floor is brick, repeating the bricks of the atrium, and hanging plants add the final touch.

The menu is simple: soup, salads, sandwiches, soft frozen yogurt and delicious desserts.

When we arrived, there were no other customers, just a few young people chatting with a friend behind the counter. He interrupted his conversation to take our order, and although it was near closing-a bleak time in many restaurants - he was able to accommodate us on everything we wanted.

Grass Roots offers only one soup, which changes every day. On my drive into Old Town that cold night, I longed for a bowl of potato soup that I had at Grass Roots one lunchtime - not the usual heavy version, but a peppery clear broth with big chunks of potato, onion and celery.The soup this night was curry, not as memorable, but a good tangy soup with meat and vegetables. The small version - really a large cupful - cost 70 cents.

Along with it, I ordered the cornucopia sandwich($1.80), a kind of huge garden special. Whole wheat honey pita bread is stuffed with bits of ham, cheese, lettuce, cabbage,alfalfa sprouts, mushrooms, cucumbers and carrots and served with a flavorful mustard dressing. There was plenty to share with my son, who was finally enticed to eat with the promise of a yogurt sundae for dessert.

The other sandwiches and salads concentrate on cheeses, avocado, tuna and vegetables, although there is a peanut butter, banana and honey sandwich we'd like to try on our next visit,. Fresh squeezed juices, including apple and carrot, also are available as well as a wide range of herbal teas and cider.

My son ordered a lemonade, which he immediately spilled, but the waiter was very helpful with our mopping up.

For dessert, my son ordered a cup of strawberry yogurt topped with granola(90 cents) and I chose the apricot nut bread (45 cents). Grass Roots also has baklava, brownies, cheesecake and a large cake-like chocolate chip cookie which is a worthy match for any around. The cookie was sold out the night we visited.

By the this time Grass Roots really was closing and my son was dissolving into restless energy so we moved our dessert out onto a brick wall in the atrium. My two-year-old was able to play and hide in the nooks and crannies of the garden - in between bites of yogurt-while I had time to finish my coffee. A nice "summer" break for $5.12 Grass Roots

In the Atrium Building, Duke and Washington Streets, Alexandria. 548-7770.

Atmospere: Carry-out casual.

Price range: Sandwiches and salads up to $2.50.

Hours: 8 a.m. to 6 p.m. Monday through Friday.

Reservations: Not necessary.

Special facilities: Accessible to the handicapped.

Credit cards: None accepted.