A calendar of your own making

Most of us carry a vague sense of the seasons. We know spring turns up sometime in March and that the first frost usually arrives before Bonfire Night, but press for specifics and the memory falters. Was it the second week of April when the swallows came back? Did the oak leaf before the ash last year, or the other way round? A nature diary answers those questions, because it keeps the answers in pencil rather than in the unreliable back of your mind.

This is not a birdwatcher's list or a botanist's specimen book. It is a plain record of what you notice on your own patch — the garden, the lane, the walk to the shop, the allotment — kept steadily enough that after a few years it becomes a personal almanac. The pleasure is slow and cumulative, and it costs about ten minutes a day.

What to write down, and what to write it in

All you really need is a notebook small enough to live in a coat pocket, and a pencil. A pencil writes when it is cold and damp, and it does not run when the page gets rained on, which it will.

Keep entries short and concrete: a date, the weather in a few words, and one or two observations. The things worth recording are the ones that mark a threshold:

• First swallow, first swift, first chiffchaff singing.
• First blackthorn blossom, then hawthorn a fortnight later.
• Oak and ash coming into leaf, and which of the two went first.
• First ripe blackberry, first conker on the ground, first elderflower.
• First frost, first hard frost, first snow, first ice on the pond.
• Fieldfares and redwings arriving from the north, and the day the last swallow left.

Add the lasts as well as the firsts. The end of a thing is as useful as its beginning, and much easier to overlook.

Spring and summer

Spring is the busiest season for the diary, and it travels north at roughly the pace of a brisk walk, so your dates will differ from a friend's two counties away. Note where you were as well as when — a swallow over the reservoir and one over your own roof are separate sightings, and the second is the one you will remember.

Summer can feel like a fallow period, because everything is green and settled. It isn't. Note the first cut of hay in the field behind the church, the first ripe strawberry, the first elderflowers ready for cordial, and the evening when the swifts start screaming low over the rooftops. Their departure in early August is one of the quietest events of the year: you rarely see them go, you simply notice one evening that the sky is empty.

Autumn and winter

Autumn gives you leaf fall. Choose one tree you can see from a window — an oak holds its leaves longer than most, ash sheds early — and note the week it turns and the week it stands bare. Then come the conkers, the sloes in the hedge, the smell of leaf mould after rain, and the frosts.

Be precise about frost where you can. A ground frost lies on the grass; an air frost means the temperature at thermometer height has dropped below zero, and it is the harder, later event. Note both. Note the first morning you scrape the car, the first day the puddles stay solid, the first snow that lies. Winter proper brings the thrushes down from Scandinavia, and on the coldest snaps, perhaps a woodcock in the wet corner of a field.

Making the habit stick

Keep the notebook where you will see it — by the kettle, on the hall table, in the boot bag. Write the day's entry while your boots are still wet. Don't aim for completeness; three lines done is worth more than a page intended.

Walk the same short route most days. Differences show up fastest on familiar ground, and a hedgerow you pass daily will tell you more than a dozen new places. If you miss a fortnight, don't abandon the diary. Date the next entry and carry on.

Reading back the years

One year's diary is a curiosity. Four years is data. You will find your own average date for the first frost, and the year the swallows were a fortnight late and everyone blamed the weather. You will learn whether your last frost really does fall around the middle of May, which is worth knowing before you put the tomatoes out, and which week the blackberries are reliably ready on your bit of hedge.

The greater reward, though, is attention. Once you are in the habit of noting the first chiffchaff, you start hearing it. The diary does not make the countryside more interesting; it simply stops you walking past it.