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Catkins tree identification


Which trees have catkins and how to identify

Catkins start to appear on trees in the late winter months and provide a cheering sign that spring is on the way. Catkins are easily identified by its long, slim shape and spiky texture. Catkins play an essential role in tree reproduction and can be found on hazel, silver birch and white willow trees among other species.

For a few weeks each year, catkins release pollen into blustery March breezes, then fall the leaf canopy unfolds. As they are blown in the breeze, the female flowers are pollinated by the pollen from the male flowers.

Enjoy them while you can with our catkin guide which explains which trees have catkins and how to identify.

What are catkins – and what do they do?

A catkin is a long slim flower which often has no petals. Catkins allow a tree to reproduce as the female flowers are pollinated by male flowers. This happens when the seed is dispersed by the wind or by insects which play an important role in helping pollination happen.

Which trees have catkins?

Hazel -

Corylus avellana

Golden catkins can be found on the bare twigs of hazel trees. The catkin releases clouds of yellow pollen that seem to dissolve in the air, destined for tiny female flowers that are just clusters of carmine stigmas protruding from a bud.

Hazel - Corylus avellana/Credit: Getty

Alder -

Alnus glutinosa

Longer, more knobbly and darker than hazel, these are the first catkins to shed pollen in spring. They’re carried on the tips of twigs, often alongside clusters of tiny red-tipped female flowers.

Alder - Alnus glutinosa/Credit: Getty

How to identify nuts and seeds from British trees

Can you spot the difference between a sweet chestnut and a horse chestnut? Or a sycamore seed and a field maple? Here is our expert guide on how to identify nuts and seeds from common British tree species.

Goat willow -

Salix caprea

This has separate male and female trees. Male catkins are clad in golden stamens; female catkins are spiky and green. Both secrete nectar – key energy for bees and butterflies in early spring.

Goat willow - Salix caprea/Credit: Getty

Silver birch -

Betula pendula

Male catkins elongate and shed pollen at the same time as leaf buds open. Female catkins are short and point upwards, hanging downwards after pollination, when the seeds develop.

Silver birch - Betula pendula/Credit: Getty

British tree guide: how to identify and where to find

Trees come in many different varieties, shapes and sizes, and many of Britain’s common tree species will be easily recognisable. Purifying our air by absorbing carbon dioxide and other harmful gases, trees are vital for the health of the planet.

Trees also provide a habitat and food for wildlife, creating an ecosystem where birds, insects and other creatures can live.

Can you spot an oak from a horse chestnut tree? Learn how to identify common tree species and the best places to see with our expert guide on British trees.

White poplar -

Populus alba

These long, fat, red-tinged catkins are often carried at the top of the tree, so you may need binoculars to appreciate them. Easily dislodged by wind, they litter the ground after a gale.

White polar - populus alba/Credit: Getty

Walnut -

Juglans regia

The short, fat, green catkins shed pollen at the same time as the leaf buds release their grip on the purple-hued foliage. Female flowers are shaped like little pots, tipped with a pair of curved stigmas.

Walnut - Juglans regia/Credit: Getty

Which trees have catkins and how to ID them

Martha Boalch

Citizen science officer

Have you ever stopped to notice the small and interesting flowers that grow on many of our UK trees? Some of these are catkins: long slim clusters of tiny flowers, with small petals or none at all. Learn which trees have catkins, why and when you can see them with our quick guide.

What are catkins for?

Essentially, catkins allow the tree to reproduce. Catkins allow the female flowers to be pollinated as the pollen from the male flowers is blown by the wind.

Once the seeds have developed they are dispersed by the wind to avoid growing right below their parent. The exception is willow which uses insects for pollination rather than wind.

Which trees have catkins?

Alder (

Alnus glutinosa)

Each alder tree has both male and female flowers. The catkins which house the male flowers are up to 6cm long. Young catkins appear green before turning yellow. The female flower is a smaller red structure, about 1cm long and with many hair-like structures across the surface. Once this is pollinated, it turns into the brown alder fruit or ‘cone’ which houses the seeds.

Alder catkins are green before turning yellow.

Credit: Nature Photographers Ltd / WTML

Hazel (

Corylus avellana)

Hazel shrubs are monoecious, which means they have male and female flowers on the same plant. They can’t self-fertilise though. Hazel catkins look like alder and also house the male flowers. The female flowers are a small vase-shaped bud with red filaments sticking out. If pollinated, these buds become the hazel nuts in autumn.

Hazel catkins eventually turn into hazelnuts.

Credit: Ross Hoddinott / naturepl.com

Silver birch (

Betula pendula)

Silver birch is also monoecious. Male catkins are 4-5cm long and yellow-brown in colour. They hang in groups of two to four at the tips of shoots, like lambs' tails. Female catkins are smaller, short, bright green and erect. Once pollinated, female catkins thicken and change colour to a dark crimson. Masses of tiny seeds are borne in autumn – they have tiny ‘wings’ on each side of the seed to help them travel on the wind.

Silver birch catkins look like lambs' tails.

Credit: Ashley Cooper / Alamy Stock Photo

White willow (

Salix alba)

White willow is dioecious, meaning male and female flowers grow on separate trees. Catkins appear in early spring. The male catkins are 4-5 cm long while female catkins are 3-4 cm long and a bit narrower than the male. After pollination by insects, the female catkins lengthen and develop small capsules, each containing tiny seeds encased in white down. These white feathery attachments help seeds to float on the wind like a dandelion seed head. 

White down makes willow catkins appear fluffy.

Credit: Florapix / WTML

Pedunculate oak (

Quercus robur)

Oak catkins appear less densely packed than those on other trees. Male catkins are yellow, each around 6cm long and grow in rows, hanging down from the branch in a curtain. The female flowers are tiny with fine filaments protruding to catch the pollen. These later become the acorns.

The catkins of oak grow in rows like a curtain.

Credit: Geogphotos / Alamy Stock Photo

When to see catkins

Many catkins appear over winter and are easy to spot on the otherwise bare branches. They tend to flower during spring, but it depends on the weather.

You can typically expect to see catkins in flower in the following months, though these dates can fluctuate. Changes in their timing may be linked with climate change. That’s why it’s important that we monitor events like this.

Recording our seasons


Catkins flowering is one of 69 wildlife events our amazing volunteers record for Nature’s Calendar. This project tracks the effects of weather and climate change on wildlife across the UK – its records date all the way back to 1736!

We ask our recorders across the UK to keep an eye on catkins on their local hazel, silver birch and pedunculate oak trees. We want to know when they appear to swell and release pollen – this is their first flowering date. 

By taking a few minutes to share what you see, you'll be adding to hundreds of years' worth of important data for studies worldwide. Every record is crucial and valuable. The data recorded helps us to understand the effects of climate change and other patterns in the natural environment. We couldn't do this work without you!

Visiting woods

Nature's Calendar

Help monitor the effects of climate change on wildlife near you. Your records contribute to a growing body of evidence on global warming.

Add your wildlife recordings

Learn more about British trees

Trees woods and wildlife

A-Z of British trees

Our A-Z guide to British trees from native species to naturalised and widely planted non-natives.

Trees woods and wildlife

How to identify trees

All trees have clues and features that can help with identification. You just need to know what to look out for with our quick guide.

Trees woods and wildlife

Identify trees with our Tree ID app

Our free Tree ID app for Android and iPhone helps you identify the UK's native and non-native trees. It's an A-Z tree guide in your pocket.

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