Seriously Studying Juniper


We’ve been working on Islay over the last several years to protect and propagate the local juniper populations that have managed to survive over-grazing. There has been additional jeopardy; a micro-oganism that causes disease (a “pathogen”) has been attacking plants on the mainland. Eleanor James is taking her PhD at UKCEH, the Centre for Ecology and Hydrology, Edinburgh; her specialist subject is juniper – and how to conserve its genetic variety. It’s important that juniper stays diverse so it can better resist climate change and pests such as this pathogen. As gin makers, juniper is our most iconic ingredient. Partly supported in her studies by The Botanist Foundation, here Eleanor gives an update on what she’s found out, a year in. 

Juniper in the UK

The common juniper (Juniperus communis) is one of three native conifers in Britain. It is the most widely distributed conifer in the world and the populations we have in Britain are at the far northwest of this range. As we have a unique oceanic climate, we might expect to see unique adaptations in our juniper that are not present elsewhere.

Once a common feature of the British landscape, populations of juniper here are now fragmented and declining. There are probably many reasons, such as low natural regeneration, a serious new Phytophthora pathogen, and land management practices, but one thing is clear: as populations decline we lose vital genetic diversity. I am studying genetic diversity in juniper, to figure out how much there is and where it grows. My results will help to protect and restore the populations we have.

Precious berries

Juniper and genetics

Juniper is very variable – some plants grow as upright trees, others as creeping shrubs. There are separate male and female plants, which may also cause variation in resource use and growth rates.

Is any of this diversity down to genetics? Or are plants changing in response to the environment without passing any of this down to the next generation?

To start answering these questions, a seed collection was made from sixteen natural populations of juniper across Britain, then germinated and grown. The resulting 935 plants are now around five years old, carefully raised under common conditions. This means not only can I measure and compare different parts of the plants (like height and diameter) easily, I can also be confident the differences are down to genetics. The experiment is particularly valuable as juniper is long-lived, relatively slow growing and notoriously tricky to germinate, and has rarely been done before anywhere in the world.

Eleanor James

Looking at the early results, I have found that populations and families share several features, showing that genes are playing a role. Generally, plants from eastern populations had longer, thicker, broader forms than plants from western populations. Needles were significantly longer and broader in plants from southern populations. In the future I’ll be making further trait measurements, recording the timing of certain life events like cone production and measuring differences in biochemistry. These genetic differences tell us that plants have adapted to different local environments, and give a clue as to how.

We can also look at DNA directly. From each of the sixteen populations, small amounts of foliage from several trees were gathered. The extracted DNA from the foliage provides a unique DNA fingerprint for each tree. Using these data I can ask if populations are interbreeding today, and answer questions about ancient movements of juniper through the landscape. I am also working to team up with collaborators to make more collections of juniper from other parts of the UK, Europe and around the world.

Getting her hands dirty

Encouraging the natural regeneration of populations would help avoid some of the risks associated with planting from nursery stock or translocating juniper from one population to another. In a third strand of my research, I spent several long days lugging fencing around hillsides and digging through tough grasses to set up seed plots. Over the next few years, these will let me test how soil water content affects germination and survival of local juniper seeds.

It’s been an odd start to my first year of PhD studies – and with a steep learning curve – but happily I’ve got lots of work underway now. Soon we will know a lot more and be well on the way to protecting our juniper trees.

Juniper in the glasshouses at CEH

Further Reading

Watch Eleanor in conversation with our in house forager James IGTV>

Read about Forager James checking on juniper populations in South Islay in 2020, by Kate Juniper Conservation>

Juniper’s Islay story, by Carl 2014 Islay Juniper >

more features

Due to regulations in your own country of residence, you cannot access this website

By entering you accept the use of cookies to enhance your user experience and collect information on the use of the website. Find out more