Local Tree Provenance

The bare-root season is almost upon us. Planting trees and shrubs bare-root is a great way to forgo pots, plants are a lot cheaper to buy than throughout the rest of the year, and they need a lot less watering when planted now. When selecting bare-root plants, there is a very important thing to consider though that is often overlooked – provenance, the place of origin.

Imported Diseases
There are fungi, like hymenoscyphus fraxineus and phytophthora, silently sweeping across Scotland, brought in from plants imported to the country, affecting large numbers of our trees. Hymenoscyphus fraxineus, known as ash dieback and phytophthora, which can suddenly manifest in alder trees, can render, otherwise healthy looking trees, dead. Our trees do not have resistance to these imported diseases.

Ash dieback Image courtesy of The Woodland Trust

The New Zealand flatworm, arthurdendyus triangulatus, is an invasive species slowly gaining ground, threatening populations of earthworms and other beneficial soil organisms. When people first discover these ugly looking creatures in their garden, they are unsure what they are looking at and unfortunately, it is nearly impossible to get rid of them. Again, as the name suggests, these critters were brought in through import from other countries. If we want to stop further pathogens coming into Scotland, choosing local provenance is an important step in the right direction.

Epigenetics
Grim pathogens and killer worms aside, trees from local, genetic material have their flowering seasons lined up with local pollinators and their dormancy patterns synched with local conditions. 

A process called epigenetics makes sure that species are fine-tuned to their environment. Selecting genetic material from abroad, growing them abroad, and then transporting plants into our climate will not give your tree the edge it might need.

Epigenetics is amazing. Years ago when I was studying, the process was illustrated to me with a post-it metaphor. DNA is like an instruction manual, determining what the tree looks like over its development and when it is mature. Epigenetics is like a post it, stuck on top of the genetic manual. Say the environment changes to be a lot warmer, this post-it has improved instructions on a genetic level to better deal with the increase in temperature.

New cells are made all the time in the tree, like when buds are formed, and when seeds are formed after pollination. Whenever such a new cell is made, the DNA is copied. And just like when we would photocopy a manual with a post-it on it, the DNA in the new cells shows the instructions on the post it, not the underlying original text. It is evolution on speed dial and that can be really useful. There might for example, be epigenetic changes that help trees deal with viruses.

Native Species
The best solution we have to overcome disease existing here right now, is to have a large pool of genetically different trees – maybe one of these varieties has the potential to be resilient. Variation is generally high in locally grown, native plants, especially when compared to ornamental varieties grown in large nurseries abroad.

Look at volunteer saplings that pop in your garden over time by themselves. Select strong ones that are in a good place or move them, and complement them with other natives from local nurseries to give our native gene pool a chance to deal with diseases.

Doing your bit is easy: when buying bare-root this season, choose local provenance where you can and celebrate the local variety and beauty that we have right on our doorstep.

Katrina Flad runs her sustainable garden design and landscaping business frock n wellies from her home in Aberdeenshire. Passionate about the planet and all things that live on it, she wanted to make a real difference to her environment ever since she can remember. In her regular column, Katrina will bring you design solutions for your garden which are sustainable, practical and beautiful. Follow Katrina at frock n wellies on Instagram and Facebook

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