Humus
Morning mist over a bog pool, pines on the shore reflected in the water

PracticePlants4 min read

A Phenological Calendar

A simple practice for the whole year: note when the first blackthorn blooms, when the swallows arrive and when the first frost falls.

By Hanna Sitowie

Phenology is the study of when things happen in nature. When buds break, when the lime trees flower, when the cranes leave. It sounds modest, but phenological notes are among the oldest climate data we have. Robert Marsham1 An English naturalist who from 1736 recorded the “indications of spring” on his Norfolk estate for over 60 years. His family carried the notes on until 1958. started his calendar in the 18th century, and his family kept it for two hundred years.

You don’t have to be a scientist to keep your own. A notebook, one place and a little attention are enough.

What to watch for

Buds, blossom, autumn colour, first frost. Four moments that are easy to notice.4 photos

Early spring

  • the first hazels and alders in flower (shedding pollen),
  • the first skylark song,
  • the return of starlings and cranes.

Spring

  • buds breaking on birch and horse chestnut,
  • blackthorn, cherry and lilac in flower,
  • the first swallow and the first cuckoo.

Summer

  • lime trees in flower (easiest to smell before you see them),
  • the first ripe cherries and the grain harvest,
  • the last screams of the swifts before they leave.

Autumn

  • beech and maple leaves changing colour,
  • cranes and geese leaving,
  • the first ground frost and the first hoarfrost.
Winter: freezing fog settling on the branches. Worth writing down too.Video: Extemporalist / Wikimedia Commons, CC0

What the calendar tells you

In Europe, spring now arrives on average a few days per decade earlier than it did half a century ago. But not every species is shifting at the same pace. Flowers can open before the insects that pollinate them arrive, and chicks can hatch after the peak of caterpillars has passed. Phenologists call it a mismatch.

A phenological calendar is a diary in which the weather is the hero and patience is the narrator.

Your notebook won’t change the climate. But it will change how you look at an ordinary tree outside your house. After three years you’ll know it is flowering a week early this year. And you’ll know that means something.