Understanding Catkins and Early Spring Tree Signs

Why the Year Really Begins with Catkins

Stand in a hedgerow on a mild January morning and the wood can look entirely asleep. Look closer, though, and the hazel is already doing something. Those little grey-green cylinders you noticed in November have lengthened and loosened into golden lambs' tails that swing at the least breath of wind. Catkins are the male flowers of our native broadleaf trees, designed to release clouds of pollen into the air long before leaves appear. Because they rely on wind rather than insects, they have no need to be showy in the way that a hawthorn blossom or a poppy needs to be — yet they are among the most reliable markers of the turning year.

Learning two of them properly — hazel and alder — gives you a surprisingly accurate calendar. Once you can tell them apart at a glance, you can walk the same lane each week and watch spring arrive in a series of small, dated events.

Hazel: The Golden Lambs' Tails

Hazel (Corylus avellana) is usually the first catkin tree to catch the eye. A single hazel bush holds dozens of catkins made up of up to eight little green buds strung along a slim stalk. In January they hang, soft and sulphurous yellow, from about two centimetres up to eight. Give one a gentle tap and a fine dust of pollen drifts off, which is exactly what a breezy February day is for.

The male flowers get all the attention, but the female flowers are the real prize for a curious eye. They are almost invisibly small — a fat green bud with a tuft of crimson threads poking out, like a tiny red star. A hand lens or a close look at a low twig is worth the effort. Hazel grows almost anywhere in hedges, coppice and old woodland edges, and its twigs are hairy and slightly zigzagged with softly rounded green buds.

Alder: Purple, Pendulous and Fond of Damp Ground

Alder (Alnus glutinosa) is the hedgerow's damp-footed cousin. You will find it along streams, in wet woodland, on the edges of ponds and in the sort of heavy clay that would finish off a hazel. Its catkins start a deep purplish-green before flushing yellow, and they are noticeably longer and slimmer than hazel's — more like a thin, rolling pin than a lamb's tail.

The real giveaway is what hangs on the twig beside them. Alder carries last year's cones: small, hard, dark woody cones, roughly a centimetre long, still attached to the branch through the winter. You will often see unripe green cones growing alongside the catkins too. That combination of purple catkins and little cones is unmistakable. Alder also fixes nitrogen at its roots, which is why it will grow happily on poor, waterlogged soil where little else thrives.

Telling Hazel and Alder Apart at a Glance

Once you have seen both in the same week, the distinction sticks. A quick checklist for the lane:

• Colour: hazel is butter-yellow; alder is purple-green turning to yellow-green.
• Shape: hazel catkins are short, fat and oval; alder's are long, narrow and cylindrical.
• Extras: alder carries small woody cones from the previous year; hazel has none.
• Buds: hazel has soft, round, green buds; alder's are purplish-brown and sit on short stalks.
• Location: alder likes wet, low ground and watercourses; hazel prefers drier hedges, banks and woods.

Other Early Tree Signs Worth Watching

Catkins are only the beginning of the sequence. In the same weeks, the wych elm flowers in tight reddish-purple clusters on bare branches, and ash puts out its dark, wind-pollinated flowers from black buds. On the ground below, snowdrops, lesser celandine and dog's mercury begin to move, and by March the smell of wild garlic will tell you where a woodland is without you needing to look.

Keep an eye out for blackthorn, whose white blossom opens on bare black twigs, usually a week or two after the hazel has peaked. That blossom is a useful local guide: in much of Britain it runs roughly with the last of the hard frosts, though the exact date shifts a fortnight or more between Cornwall and Aberdeenshire. Then come willow catkins — silvery, soft and round at first, hardening later — and birch, whose slender catkins are longer and more upright than either hazel or alder.

Birdwatchers get a bonus. Siskins and redpolls flock to alder cones through the winter, hanging acrobatically to pick out the seeds, while tits work hazel for the nuts they will not find until September. Early tree pollen is also worth noting if you are a hay fever sufferer: hazel and alder are the first significant sources of the year, usually from January into March.

Bringing It Home to the Garden and Hedgerow

There is a practical side to all this watching. Bare-root hedging is planted between November and March, so if you want hazel in a mixed native hedge, order it now and get it in while the ground is workable. Hazel responds beautifully to coppicing: cut stems back to a low stool between autumn and early March, while the sap is down, and the result is a supply of bean poles, pea sticks, stakes and binders for the year.

Alder is the one to plant where drainage is poor and nothing else will hold the bank — though be prepared to keep it in check, as it suckers freely when happy. Above all, keep a small notebook. Date the first hazel catkin you see, then the first alder, then the first blackthorn flower. Two or three years of those notes and you will have a personal record of spring that is far more interesting than any forecast.