The first time I ever heard of a phenological tie-in was years ago, when someone pointed out that it's time to look for morel mushrooms when the oak leaves are as big as squirrels' ears -- and called it a phenological tie-in.

It's a memory trick, too. Now when the oak leaves are that size, they remind me to look for morels. And I've noticed that both of these things happen when the wild asparagus is just starting to grow into ferns, and when sweet woodruff is in flower. If I hit it on the button, I can eat morels with late stalks of wild asparagus and drink woodruff-flavored May wine.

This phenology, the study of periodic bilogical phenomena, such as flowering, or insect migration, and how these phenomena relate to climate. It sounds techinical, but actually, it's such a simple concept that farmers, peasants, American Indians and nature-lovers used it long before there was a scientific definition for it.

Nature is capable of incredible surprises and seasonal changes, but the events that occur simultaneously almost always do so, and they do it with enough regularity so they can be predicted from year to year. And they play off one another, and predict one another, and tie one another together until nature becomes visible to the observer as a miracle of timing.

Shad come up the rivers when the willow leaves are as big as mouse-ears. Wild raspberries ripen when the milkweed flowers. Elder and honeysuckle perfume the air at the same time.

Farmers have long claimed that appleblossom time is the time to plant cool crops, and that lilac season is the season for sowing hot-weather crops. Folklore says that a cold spell, called a "dogwood winter," is likely to come when the dogwood is in bloom.

And so a season is divided into periods, even smaller seasons of natural events. And, by observing these events, people can learn a lot about nature, and make practical use of the knowledge.

There are complex reasons for natural events' occurring when they do -- temperature, rainfall and, perhaps most important the length of days and nights. Spring flowers bloom as the days shorten, and fruits ripen.

And the phenomena that happen together happen together -- their season might be a week early or late, but, within that little season, there's incredible order. So I start looking for inky cap mushrooms, and maybe even a spring crop of oyster mushrooms when the cherries are in bloom, and I go to gather cherries when the elder is in bloom. c

I've yet to see a work, even for one area that ties nature together in this way. But because natural phenomena make a much more accurate garden calendar than planting dates, it's worthwhile to keep a personal calendar for your particular place.

It's hard to notice everything that's happening in a season, but if you keep a day book and jot down what you see and smell, what's blooming, and a few specifics about what's happening, it will give you the beginnings of a timetable.

Keep a record of unusual weather, hard rains, late frosts, freak hailstorms and things like that -- even a temperature log. It will help you see weather trends, and to decide whether, as oldtimers claim, dogwood blooms are always accompanied by cold weather.

If you keep such a record, even week by week, for a few years, and constantly combine the information, eventually you'll have a volume that tells a lot about nature's timing in your area.

It will become a book of pehnology, and you will become a student of it, schooled in nature's classroom, to see even the small shifts in season -- to see that for everything there is a season, and that a year has many more seasons than simply summer, fall, winter, spring.