Amazing year for aspen at Insh Marshes

Excitement is high for many people in the Badenoch and Strathspey area, including staff at our Insh Marshes nature reserve, as the aspen trees are in flower all across Scotland. This is the first time in 23 years that there has been a mass aspen flowering here. RSPB Scotland’s Jen Mullen tells us more.

Amazing year for aspen at Insh Marshes

The facts

A mass aspen flowering event is happening across Scotland right now. The last time there was a major flowering of aspen in this country was in 1996, following the hot summer of 1995. These trees will generally only flower and set seed here following a hot summer. Mm , just like the one we had last year!

Aspen (Populus tremula) trees are native to the UK but it is rare to encounter a full aspen wood. They mostly occur as small stands of trees and sometimes individual trees. They are extremely vulnerable in Scotland. It is thought that aspen have suffered more from deforestation than any other native tree in Scotland, largely because of this sporadic flowering, relatively short lifespan and being very palatable to grazing. Once aspen has been lost from an area, it is unlikely to be able to return on its own. 

Aspen at Insh. Credit: Cat Vis Christie

The trees

Aspen is a deciduous broadleaf tree. The scientific name ‘tremula’ means ‘to tremble’ which refers to the way the leaves shimmer and make a rattling sound as they ‘shake’ in the wind.

Aspen is most common in the Scottish Highlands but, even here, it occurs in small and isolated populations. There are only a few aspen dominated woodlands left here and one of those is at our Insh Marshes Nature Reserve.

Unlike most trees, where male and female flowers are present on one tree, aspen have both male and female trees. When conditions are right, the trees flower in March and April before the leaves appear. Both male and female trees produce catkins. If the female catkins are successfully pollinated, they will ripen in early summer and release tiny seeds which will grow into new trees.

When conditions aren’t right, it doesn’t mean that the trees do nothing. They can also reproduce asexually by sending up shoots (called suckers) from their roots. These shoots grow into trees that are clones of the parent tree. This is the most common way for aspen to reproduce in this country. So, when you look at an aspen wood here in the Scottish Highlands, genetically it could all be made up of the same tree.

Credit: Cat Vis Christie

What makes aspen special

Aspen supports a wide range of animal and plant species, some very rare and many only found associated with aspen, like the aspen hoverfly. The aspen hoverfly is one of the UK’s rarest hoverflies and it is found at only a few sites, all of which are in Scotland. One of those sites is the aspen wood at our Insh Marshes Nature Reserve. Aspen hoverflies have been present at Insh Marshes for possibly thousands of years and they are regularly recorded on the reserve. Their larvae require decaying aspen wood to feed.

Aspen is also very important for many rare mosses and lichens, for example aspen bristle moss. This rare moss was thought to be extinct in the UK until it was rediscovered in Rothiemurchus in the 1990s.

Credit: Cat Vis Christie

What is being done to help

One of the factors affecting aspen woodlands from regenerating is the way in which it predominantly spreads vegetatively (by sending suckers out), and not by seed which would be dispersed widely. The suckers can be vulnerable to grazing and excessive browsing by deer is a serious issue for aspen conservation. It could result in preventing these woodlands from expanding. Deer populations require to be managed by humans in the absence of their main natural predators. The team at Insh Marshes monitor aspen regeneration in the woodland regularly to help ensure that this rare and ecologically important native tree continues to thrive. This flowering event could be an excellent opportunity for the team to collect some seed to help with this work.

If you would like to experience the magic of a rare aspen woodland, join one of RSPB Scotland Insh Marshes Nature Reserve’s guided walks this spring and summer. More information can be found here: https://www.rspb.org.uk/reserves-and-events/reserves-a-z/insh-marshes/

Have you spotted any aspen trees flowering? Let us know in the comments below!