Alder (Alnus glutinosa) is a broadleaved tree that is native to the UK and one that the Wild Ingleborough Programme is planting out among many others in various reserve areas that make up Wild Ingleborough. It is a species that is not immediately striking in stature, nor the most useful in terms of timber, but one I’ve come to know over the years as a crooked, purple tinged pioneer of wetlands and riverbanks. It just so happens to be my personal favourite tree!

Getting to know the alder

Once you ‘get your eye in’ for the alder there’s no mistaking it for any other tree. The signature cone shaped outline makes them easy to recognise from near and afar, in winter and in summer. alder trees prefer wet, damp habitats and their presence in an area should give you some clues about the habitat they are growing in. An alder is very likely to be close to water, perhaps a river bank or flood plain, or maybe an area of upland that gets high rainfall with waterlogged soil.

As a young, budding shoot, the alder has a light orange hue to its stalk with small pimply nodules on it, contrasting beautifully with its pastel, lilac coloured leaf buds. The purple buds are one of my favourite features and one that is a useful ID clue in winter.

As the tree matures, its trunk becomes deeply fissured and rough. Its branches are often gnarly as it bends over the river bank, its bark turns darker and hosts tree loving lichens as it grows. When allowed to grow in an open area, the alder canopy grows into a distinctive cone shape with the branches growing out from the trunk horizontally.

It has large and glossy green leaves that are roughly heart shaped and produces male and female catkins. The female ones are like ‘lamb’s tails’, similar to Hazel, and the male catkins are like miniature pine cones that start green but turn hard after pollination.

Look out for the small, woody cones in the twigs and on the floor - they are a great identification feature as alder is the only broadleaved tree to produce cones like this.

Habitat and history

If you look at a map of the Dales or other areas of England that were settled by the Norse and Danes during the Viking Era, you may occasionally come across the place name, ‘Eller’. Indeed, if you look around Chapel-le-Dale and Ribblesdale which flank Wild Ingleborough you will see ‘Ellerbeck,’ ‘Ellerbeck Pasture’ and ‘Ashes Eller Bank’, the latter forms part of a drumlin within Ashes Pasture.

‘Eller’, is the Old Norse term for alder, and seeing the words ‘alder’ or ‘eller’ in any place is a clue that if there aren’t alder trees there now, there probably were when it was named! This is a useful word to know to give us clues of historic habitats and gives us a positive indication that planting alder in areas named after it can result in an established wet woodland habitat. ‘Eller’, is where the alder wants to be!

I mentioned earlier that alder timber is not the most useful, but one use that alder has seen for thousands of years is its ability to make good charcoal, a crucial fuel in the past. It is not hard to imagine the ancient people who lived around Ingleborough going down to the banks of the Ribble to cut and coppice the alder for fuel.

Biodiversity boost – alder’s influence

At Wild Ingleborough we want to introduce trees to key areas not only to increase the tree cover in the Dales, but to also allow wildlife to thrive. As a wetland pioneering tree, it has numerous benefits to a range of organisms.

Introducing the alder to bare ground gives structure to the terrain with the stems, acting like scaffolds that mosses, lichens and liverworts can use to grow up and around. The catkins produce pollen and nectar when in their flowering stage which helps bees and invertebrates survive in the months when resources are scarce. When in seed, the catkins will provide food for seed eating birds like the finches, especially goldfinches.

There are also several species of moths which use alder as their foodplant for their caterpillars, particularly the alder kitten moth. A shiny metallic blue beetle called the alder leaf beetle can often be found feeding on the foliage of alders, sometimes in big numbers, leaving telltale holes in the leaves.

Eco services of alder

This pioneer of a tree is well adapted to seed into bare and soggy ground where no other trees are growing and begin to create habitable conditions for the next generation of incoming trees to establish. It does this by ‘fixing’ nitrogen into the soil with the help of a bacterium called Frankia alni which is able to absorb nitrogen from the air so that the tree can use it. In return the alder trades the nitrogen for sugars which it produces through photosynthesis, and because of this mutually beneficial relationship it increases the fertility of the soil to enable more trees to succeed in the future.

Through our tree monitoring of planted trees from previous seasons we have found that alder seems to be targeted by deer browsing much less than other species such as rowan. We think this might have something to do with the higher levels of tannins in the alder making it less palatable, which helps our trees survive and stand a better chance of reaching maturity.

Final thoughts

I hope this blog has informed you of the various good reasons why we plant this remarkable tree species at Wild Ingleborough, and the cascading benefits that nature will use to become resilient in the face of increasing challenges for nature in the Dales.