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Jamie Blake's guide to Invasive species: Pt 2

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Photograph by gailhampshire

Last month we spoke to Jaime Blake, Bressingham’s head gardener, about the invasive species that keep him awake at night and how they affect his job taking care of our gardens - he told us so much we decided to spread it over 2 posts.

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

The biggest problem is probably the vine weevil, which many years ago was only considered to be a problem "under glass" because they weren’t hardy enough for outside, but they certainly are now!

The vine weevil is terrible for finding out and eating anything with a thickish, woody root - so that’s Primula's, Geum, Astilbes and Bergenias (Elephants Ears) amongst others.

Vine Weevil are "radical feminists"! (Green fly are the same) - it's been discovered that they don't need men, so you rarely find an adult.  They are about the size of a ground beetle, but brown rather than black.

They can lay 20000 eggs a year completely asexually. Even if only half of those survive their population will increase exponentially.

Nursery's are a big spreader of them because they stock a lot of plants all together which invites a lot of pests in.

Originating in China, Muntjac deer are another problem, they roam freely through the gardens and eat as they wish.

We have to have a certain amount of deer control on the estate, the shooting of things like Roe or Red Deer are strictly controlled (with restrictions regarding times of year, age and sex of animal), unluckily for them Muntjac’s, like grey squirrels, were cleared to be shot at any time of year.

Another invasive species is Lily Beetle - everybody groans at any talk I do when I mention this one!

It’s a Scarlet coloured beetle which is very visible on the plant - when you go and pick one off, if it drops to the ground and lays on its back it’s soil coloured making it very hard to see.

They eat everything of a plant - the flowers, the stem, leaves even the actual bulbs themselves!

What new invasive species are you planning for?

We're very blasé in this country about how many different types of plant we’re able to grow native to different parts of the world - but obviously, if we can grow the plants, we can probably grow the pests as well!

There is a new invasive species that I'm bracing myself for even though it hasn't got to as in Norfolk yet.

It was first discovered in Wisley Gardens a few years ago and it affects Agapanthus (African water lilies) - It's a tiny maggoty thing that attacks the flowers before they are open resulting in a horrible stumpy mess.

The experts don't currently know much about them but think they came in from South Africa on live plant material.

It’s the same old story - outside of their natural environment they don't have the limiting factors that kept them in check.

There are some lovely varieties Agapanthus that I’d like in the garden but I simply don't dare just in case I introduce a new pest!

When I first arrived at Bressingham, about 30 years ago now, I felt really picked on because it was around the time the Vine Weevil problem exploded and became a big problem!

I've reached a sort of understanding with them, but we still get bad years with them.  One of the things I do is keep the beds as clean as possible in the winter months, exposing the crowns of plants to the weather.

The other thing I find can have an impact is my flame-gun - which is a real boys toy!

In the winter, when the Hemerocalis have finished, one of the ways to clear up the dead foliage is to set fire to it.

We've never hid the mite problem here that other people have reported, and I think it’s measure like these that are the reason.

What, in your opinion, is the worst invasive species of animal?

The one that was a big issue maybe 20 years ago is the New Zealand Flatworm, which isn't actually a problem to our plants but it predates earthworms.

There was a big issue with it in Ireland when it was found to be responsible for the degeneration of meadows.

They came originally from New Zealand (unsurprisingly, given the name), they exist only on one small part of one Island, they’re limited in their range by steep mountains. Plants were collected from there and came to botanic gardens in this country.

We got them because Alan Bloom used to swap plants with some people in Edinburgh, Kew and Cambridge botanic gardens.

I was the one who first discovered it in a garden here, they behave like a Lamprey - they attach themselves to the earthworm and secrete digestive juice which dissolve it, then flatworm absorbs the resultant goo.

Unlike the myth about being able to cut an earthworm in half to create two worms - it's actually true in the flatworm's case, so it’s a real problem!

I remember a conversation with a University Professor when we first identified them at Bressingham.  When I asked for his advice on how to deal with them, he suggested the best thing was to leave them out on a dry surface.

Then he used a great phrase, I'd never heard it before - he said they will "Auto digest"!

In terms of what they are doing, the Flat Worm is probably the worst - they undermine the whole system, because without earthworms we're a bit stuffed.  It's a big issue that I think people have forgotten about.

New Zealand flatworm a pretty widespread but most people don't see it or notice it.  The weed proof barrier you see in many nursery's,for example, now being used by people in their gardens to suppress weeds can create conditions underneath that are perfect for the spread of New Zealand Flat Worms because it's shaded, nice and damp and has a good supply of earthworms!

Do you have any favourite gardening tips or stories?

Horticulture is such a massive subject we always welcome suggestions and experience from visitors.

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