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A gardeners guide to Invasive species

Bressingham -garden -spring -2

One of the trickiest issues any gardener has to face is the problem of harmful invasive species - We decided to get Bressingham head Gardener to talk to us about them.

He had so much to say we’ve had to split it up over 2 posts! (you can read part 2 of Jaime's guide to invasive species here)

Are all invasive species problematic?

When it comes to invasive species we only tend to think about the ones that are causing us trouble.  If something "invades" the garden that does no harm or actively benefits then they wouldn't get mentioned.

But having said (lending weight to the theory) that I can’t think of any that are beneficial!

The problem of invasive species has been going on a long time - Dutch elm disease, for example, came in on imported wood.  Other things that come in they are" wilts" that gets into the Sap stream of plants.

The biggest single problem with an invasive species is that they are out of their natural environment and, because of that, they have been removed from any natural predators or constraints that existed in their natural environment.

For example, Japanese knotweed and a Rhododendron Called Ponticum are out of their natural environment where there would be some other species that eats them, or they are limited in growth (by geology or geography, for example).

Outside of that there are no limits!

What are the most common invasive species of plant you have to contend with?

The most species of invasive plant would be something like Ground Elder, which has been with us a long time - it was one of the things that the Romans did for us!

Another is Oxalis, who’s foliage looks like that of clover, are also terribly problematic.  They run and seed around and produce masses of bulbils.

Yet another common invasive species of plant are Alliums, some species of which have become more of a problem for us - I don't know how they got here at Bressingham (probably binds) but they are here now!

There are a lot of the plants we grow here that are not indigenous have started to become a little invasive, I think because of climactic change.  Things like Gold Rod (Solidago), which seed around and run underground more than they use to.

We never used to get much in the way of seedlings from our Asters, but they are regularly seeding now and becoming a bit of a problem.  The same is true at a lot of ornamental grasses that we grow.

There are other plants that we’ve had here quite a while that are becoming invasive with the changes in climate and conditions which aren’t as obvious - things such as Crocosmia spread under the ground.

What can the gardener do to manage invasive plant species

Warmer summers, longer-drier times leading to wetter winter, -which you would have thought would hinder a plant like the Aster - but it hasn't. Climate change actually suits some plants very well!

So one of my jobs in the winter months which we'll start in January, is going round some of the groups of plants that tend to run beyond their own space and chop round them with a spade and dig out the pieces that have run out where they should be.

That’s a big job for us, every year it takes 2 or 3 weeks!

It's something we've always had to do, but it's noticeable that the spread seems to be greater. The long summers do mean plants can spread beyond what is normal. In times of drought plants reach out further for water - that has had an impact too!

So it turns out things grow if you water them, if you don't water them they grow even better!

(Don't forget, you can read part 2 of Jaime's guide to invasive species here)

Is there anything we should’ve mentioned?

Do you have any thoughts, comments or views on dealing with with UK invasive species?

Is there anything you think we should have mentioned?

If there is get in touch and let us know – you can also do it on Facebook or Twitter.


By Alastair Baker at 15 Jan 2019, 00:00 AM