Collecting holly with the UK National Tree Seed Project

The aim of the UK National Tree Seed Project (UKNTSP) is to provide a national repository of plant material and associated knowledge for long-term conservation, and to make this available to improve understanding and management of tree and shrub species in the UK landscape. Collections need to be genetically representative of UK populations and must also comprise sufficient seed numbers to support such conservation and research activities. The holly populations from which we collected seed on our most recent trip met our Peak District area upland collection target; for each collection, we wanted to capture individuals with traits well adapted to the local environment.

Ilex aquifolium is an iconic and traditional winter decoration due, in part, to the bright red fruits that appear late in the season and the fact that the species is one of few British woody angiosperms to retain its leaves over winter (1). Whilst it is a bonus for Christmas festivities, this late seeding means that special seed collection trips are normally required for Ilex aquifolium as it is rarely possible to collect other species at the same time. As this trip testifies, the time of year means that collecting conditions can be abysmal!

Ilex aquifolium in the Peak District

The collection team, including Kew scientists Frances Stanley, Rachael Davies and I, visited sites across the Peak District to collect from different upland populations of Ilex aquifolium (250-300 m). The team arrived in the Peak District in torrential rain and failing light, conditions that meant we were unable to search the site or start collecting.

The second day provided a relief from the torrential downpour but ground conditions were far from ideal, especially as certain areas of the sites we visited were somewhat flooded!

The first site contained no seeding individuals, so after an unfruitful morning the team moved to the southern side of Millers Dale. Here a number of mature individuals were found, some of which were seeding. Finally, a collection could begin.

On the third day, the team visited a National Trust site on the western slopes of Kinder. This was the highest site with the best weather and views. As Ilex aquifolium is predominantly a lowland species, the height of this site provided poor growing conditions, so individuals were rather sparsely distributed, with few producing seed.

It is extremely important that the project conserves the genetic diversity of such individuals surviving at the edge of their ecological niche. Fortunately, the individuals fruiting had a considerable amount of seed, making a large collection possible. We also collected field data, tissue samples (for DNA extraction) and herbarium specimens alongside the seed.

The last day involved returning to Kew’s Millennium Seed Bank (MSB) to hand over the collection for processing and banking.

The future of the seed collections

The UKNTSP has a wider focus than simply collecting and conserving seed. Its research activities seek to overcome current constraints to seed banking woody flora in the UK through studies on seed dormancy, germination and storage, as well as genetic studies (2).

Germination protocols are essential so that staff at the MSB can monitor the viability of collections over time and ensure that new plants may be generated from our seed collections. Germination is straightforward for many species but Ilex aquifolium has a deep morphophysiological dormancy (3,4). The UKNTSP germination team is working on improving dormancy breaking of Ilex aquifolium collected in the UK, which has proved more complex than expected in comparison with Ilex aquifolium found elsewhere. A long temperature treatment period - warm, to less warm, to cold - is being used to break UK Ilex aquifolium dormancy.

Once the current work is complete, the UKNTSP will have built national collections for the 70 targeted species banked at the MSB. The most obvious and ideal use of the collections would be the establishment of provenance trails, not just for typical tree improvement but also for potential climate change resilience. Collections could also be used to screen for pest and pathogen resistance, or to determine prevention and treatment methods. The DNA from the collected seeds can be used as a baseline to determine population and species change over time, or as a source of traits that could become apparent in potential provenance trails. The UKNTSP is also providing data and, potentially, material to contribute to the creation of local provenance seed orchards.

A botanical analysis of an arboreal Christmas carol

Hopefully this blog post has provided a seasonal insight into the UKNTSP's work. It set me thinking about the botanical merits of the popular carol, “The Holly and the Ivy”, which has multiple arboreal references but, from a scientific perspective, has a number of shortcomings!

The first concern is the lack of botanical names in the first line which, while better lyrically, are not scientific. The second line, while poetic, lacks clarity - “full grown” has no scientific definition. ‘Wood’ in the third line is a described UK habitat type but surprisingly, there is no standard scientific definition of a tree. Also, Ilex aquifolium bears no crown but is relatively unusual in the fact that it is diecious, meaning the species has separate male and female trees. Deer in the sixth line is best corrected to its taxonomic family name Cervidae. To overcome these issues a more scientifically accurate (and possibly less poetic!) alternative first verse is proposed below.

Original

The holly and the ivy,

When they are both full grown,

Of all the trees that are in the wood,

The holly bears the crown,

O the rising of the sun,

And the running of the deer,

The playing of the merry organ,

Sweet singing of the choir.

UKNTSP alternative

Ilex aquifolium, Hedera helix,

When reaching fruiting stage,

Of all the species observed in the wood,

Ilex aquifolium is diecious,

O the turning of the earth,

And the running of the Cervidae,

The collecting of our many seeds,

Seasonal analyses at Kew.

We would appreciate hearing a performance from anyone feeling up to the challenge!

Acknowledgements

The UKNTSP would like to thank the National Trust Peak District team and Derbyshire Wildlife Trust for their assistance and cooperation, and players of People’s Postcode Lottery, who have provided funding for the project.

References

Kew Science; Discover plants and fungi; Ilex aquifolium (common holly). Available online
Kew Science; Projects, UKNTSP; UK National Tree Seed Project. Available online
Gosling, P. (2007). Practice Guide: Raising trees and shrubs from seed. Forest Research. Forestry Commission, Edinburgh. Available online
Sagrario, A. & Suarez, F. (2004). Germination and seed bank depletion of holly (Ilex aquifolium L.) in four microhabitat types. Seed Science Research 14: 305–313 DOI:10.1079/SSR2004180. Available online