QUESTION: All the instructions I see for planting bulbs in window boxes say they must not freeze. But why? Freezing does not seem to bother bulbs planted in the garden.

ANSWER: The bulbs in the garden are insulated by the earth. Eight inches below the surface, soil freezes very slowly (if it freezes at all). This gives the bulbs plenty of time to make strong roots before they freeze (if they freeze at all). And a frozen garden is not as cold as it looks. Even when frost goes deep into the ground, the ground is seldom much colder than 20 degrees or so.

The soil in containers, on the other hand, can rapidly become as cold as the air, plummeting to 10 degrees, zero or below. It can thaw just as quickly. And it often does both, over and over. Hardy bulbs cannot take temperatures that low. And they can also be killed by repeated freezes and thaws. So the standard advice is do not try.

But before the legions take out their pens, let me add that failure is not guaranteed. The key to success is to mimic the earth: The larger the container in relation to the bulb, the better the chances of spring bloom. Try crocuses and grape hyacinths instead of giant tulips. Start early. Apply several layers of bubble wrap. And don't say I didn't warn you if it does not work out.

Address questions to Garden Q&A, The New York Times, 229 W. 43rd St., New York 10036, or by e-mail to gardening(at)nytimes.com. Those of general interest will be published. Unpublished questions cannot be answered individually.

By N.Y. Times Service