Hello, my name's Lindsay Turnbull and I'm an associate professor in the Department of Plant Sciences
at the University of Oxford, and we're right in the middle of this very serious corona virus crisis right
now. And my students are all stuck at home and we want to keep them in touch with biology
and keep in touch with us. And so we're going to make a new series of videos and they're going to be called back garden
biology.
Well, welcome to this episode. Back in biology, I'm going to look at the plant today that most
gardeners, I think, would be pretty confident to just cool of weed and they wouldn't allow it to grow in their gardens.
So some of the plants we've looked at so far are like primroses and the flotilla arrays and
the Longuet are native plants or close to native plants. The flotilla was probably brought
to Britain in around the 15 hundreds. It has naturalised itself very well and it's certainly native
to northern Europe. But most gardeners are happy to have these things in their garden going
as far as actually buying them and garden centres and deliberately planting them. But this plant
is not something I've deliberately planted, but I'm allowing it to grow in my garden. And if you just pan
left, we can see that there is quite a stand of it here, growing in my garden
and in the back corner where it's not doing any harm to anyone. And I quite like kids. And its
name is Garlic Mustard and its common name when one of its common names
is Jack by the hedge amounts, because it always grows in this where you see these stands
of it just growing the long side hedges. It can't invade grassland, it seems,
and it rarely invades the woodland itself. So there's just this narrow strip of habitat where it
can grow extremely well and you can find a lot of it. Now, if we just zoom in a bit more
closely and see what it looks like, you can see these are obviously
flowering. You can see the small white flowers appearing at the top of the plants. They just have four
petals. And those little four petals, flowers are typical of the
brassica family. So this belongs in the brassica family. And that's the
cabbage family. Right. So we eat lots of brassicas. And if that this is edible,
I don't personally. But it is edible. And if I take a leaf, Marbury's it. Then I get an amazing
smell of garlic. Right. So it's not a typical brassica smell. It's got
a very strong smell of garlic and garlic. Of course, we associate with a completely different plant family.
The alliums, the onion family, they are famous for producing garlic compounds.
But this brassica can do that as well, as well as having the sort of mustardy
flavour of of some of the brassicas because mustard that you actually eat in a jar, that they are
the seeds of a mustard plant farmed. So it's related to this also in the in the cabbage family.
It used to be widely eaten. It was a very popular thing. And for that reason,
it was taken from Europe to North America by settlers who wanted to
have this plan, which they considered to be valuable for food and for various medicines. They took it
with them. And that has created an enormous problem in North America. And
this is not the only plants we've done that. So when many plants from Europe, which appeared to be quite
well behaved here, didn't really cause a problem, are taken to other parts of the world,
they can suddenly cause very big problems indeed.
So I brought in a piece of the garlic mustard. I just cut it off and placed it on this tray so we can look at it
a bit more closely. You can see it has quite large leaves with a
sort of a little bit of a heart shaped base and then there to around the edge. This
is a two year old plant. I know that for sure, because garlic must that is what we call a biennial.
That means in the first year, it just forms a rosette that doesn't flower. In the second year, it flowers
and dies. So it never last very long. So it has these large, quite soft,
thin leaves. And you can see they've already suffered quite a lot of damage. You can see little holes
in them or they've been nibbled away at. And if I move up a bit further, we can see
even more holes here. So things are eating this plant. And if we move up to the
top, we can see the sort of business end of the plant and a bug just ran out at me. This
is the flowering part. And a lots of the insects I've been seeing on here are concentrated on this.
And you can see the little white flowers with their four petals.
And in here you see the developing seed pod. So they're just starting to develop
now. Must hold it against the white background. You can see they are going to be long, thin, upright seed
pods. And inside there's the seeds will develop. What's interesting about
here, I'm going to show some little bits of clips that I've taken. I've been monitoring the plants for the last week
or two while I've been flowering and just trying to take pictures of all the things I see on there. And
they're covered in insects all the time. In fact, this plant in its European native
range has sixty nine different inset herbivores that eat it. None
of them look massively impressive. Perhaps you don't even realise that they are having an impact
on the plant. They are. They are things like tiny little weevils, tiny little pollen
beetles and all those things that eating the business end of the plant. They are reducing
its fitness and taking away its pollen, which means it can't so successfully pollinate. The plants,
they're eating, the seed pods themselves. And one of our most charismatic insects that we're most
interested in having perhaps in our garden, the butterflies and the orange tip butterfly, which
is a very attractive butterfly that you might see flying around your garden at the moment, is white with orange tips
to the four wings. The females lay their eggs on this plant. And when they emerge,
they eat those developing seed pods. And all those things take a toll on the plant
and probably help to prevent it from being too successful. And that's
one of the problems when we take a plant somewhere else and when we take this plant to America, it may
well be that people just took the seeds and therefore all the insect passengers didn't go
with it. And what happens in the States is you don't find all these insects on the plants at all.
That was virtually nothing. They're eating it because they're insects are not adapted to this
plant and it's unique chemistry. All plants have a unique chemistry and insects have to be coevolved
with their host plants. And that is probably contributing to
the problem in the States. And they've been doing some trials with some of the weevils
that we have here that eat garlic mustard to see whether an introduction might be possible.
People are very reluctant to introduce yet more things even as biological
control agents, because what we know is that although they're supposed to only garlic mustard,
you know, this is a brassica brassicas are a commercial crop. And if those weevils turn
their attentions to broccoli or cabbage, you'd suddenly have a new pest species to deal
with. And so perhaps that's why that permission has not been given.
If you're not sure how to identify Weevil, but you're interested in what it looks like, a weevil is a little beetle with a
very distinctive head into the straw one for you now. So the head
looks like this had me either down here and they have this amazing
rostrum. My antennae normally come off around here. And on the end of this rostrum
are the mouthparts. Most weevils eat plants and they use the mouthparts on the end to often
chomp into the plants and then lay their eggs inside them. Some of them live below ground
on the roots and some of them live above ground on the leaves. And a little grey weevils are the ones
we've seen on the garlic mustard. So what exactly have we seen on the garlic mustard?
Well, here you see the sort of inset falls that constantly hangs around these plants, tiny
little midges or parasitic wasps that we can't even see properly. Close up here,
the little pollen beetle, a shiny little guy who lives on the flowers. I'm walking
up and down the stems. Here are two of those little grey weevils. I managed to catch
one in my hand and here he is and freeze frame. And we can see that tiny little rostrum
there, almost like a little elephant's trunk. When we took that plant out of the tray, there was this bug
running around wildly. Again, I'm really not sure what species that is, but where there are
prey, there are predators. And this is the rather handsome 14 spot Lady Bird who is crawling
around the plants and also things coming to the flowers. This an early hover fly.
And, of course, the pest resistance, the orange tip butterfly itself didn't manage to get it on the garlic
mustard, but here it is, having a rest on a daisy and the more. So I want to finish
this piece, not back exactly where I started, but on the other side of the garden where there's something
that gardeners will be a lot more comfortable with. This is Camastra. This is a North
American plant. It's been brought here and it's grown very widely in gardens
and plants like this sometimes. Give me pause for thought. It grows very well. It
forms very large clumps. We know that in its native North America, it can form
very dense patches in wet meadows. And you start to wonder, well,
what if this plant escaped from my garden and started to establish in the U.K.?
Could it become a difficult, invasive one that we would then have to spend a lot of money
getting rid of? Like Japanese knotweed and we just don't know. Gardens are harbouring
hundreds of plants that have been brought to Britain from all over the world. And rather looking
thought, frankly, puts into wondering which ones of them will become problematical
and which ones are bad ways. We know that most don't because that they have to be cossetted and
gardens gardeners have to work really hard to grow them. But you certainly don't have to work hard for this thing. It's
very easy to grow. It thickens up and grows very well. And what you can say
is, unlike the garlic mustard, I can see virtually no insects on it. You know, it's advertised
as being pest free, disease free, trouble free. What that means is that none of our native
herbivores actually eat it. And that could mean that something like this in
50 years time, rather than admiring it, we might be seeing this as a brand new villain of the piece.
So what can you do in your garden this week? Well, have a look around. What native plants.
Have you got. Popping up in your flower beds that perhaps weren't invited, but perhaps. Are there any
way. And can you see those tiny little bugs and insects? They're little
aphids. The little weevils that little pollen beetles. All those things that we saw
on the garlic mustard. And remember, all those things are playing their part. They're stopping
those plants from becoming too invasive and dominating everywhere. And they're also food
for the things we like best. I see all those little birds that are foraging around your garden,
too, till next time. Have a great week.