Gardenbite: Teasel - An invasive species coming to a roadside near you? | #GoodGrowing

If you’ve driven along any interstates or highways in Illinois, there’s a good chance you’ve seen tall plants with spiky flower heads. Teasels have become an increasingly common sight across Illinois. While they may appear attractive, especially for cut flower arrangements, these troublesome plants can form large colonies that outcompete and choke out native plants.

 

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Episode Transcript

Ken Johnson (00:04):
Welcome to the Good Garden podcast. I am Ken
Johnson, horticulture educatorwith the University of Illinois
Extension, coming to you todayfrom Jacksonville, Illinois with
a Gardenbite. On this week'sgardenbite, we're gonna talk
about a plant that if you'vedriven along the interstates or
highways here in Illinois,there's a good chance that
you've encountered, and that isteasel. Teasel is becoming an

(00:25):
increasingly common sight herein Illinois. So what exactly
does this plant look like ifyou're not sure?
So here in Illinois, we have twospecies that we commonly find,
cut leaf teasel and commonteasel. And both of these
species are gonna grow as abasal rosette, basically a a
clump of leaves that grows lowto the ground. The leaves are
going to be puckered, with scalpedges for both species, and

(00:49):
while they're growing as arosette, they're going to
develop a large taproot that canbe over two feet long and an
inch in diameter when it's kindof, quote unquote, fully grown.
And we commonly describe teaselas a biennial plant. However,
it's probably more accurate tocall them a monocarpic
perennial.
And these plants, thesemonocarpic perennials are plants
that are going to produce fruitand seeds once, and then the

(01:11):
plants are going to die. Whereaswith a biennial, they produce
this rosette the first year, andthe second year, they flower. So
this would be something like acarrots where we plant the
seeds, we get the large rootthat we typically harvest. But
if you would leave that carrotin the ground, that second year,
they're gonna produce a flower,produce seeds, and that plant
will die. Parsnip would beanother example, of this.

(01:34):
And the reason it's probablymore accurate to call them a
monocarbolic perennial isbecause the size of the rosette
is a better indication of when atesla plant is going to flower
rather than the age. Sotypically, when a a tiso plant,
that rosette gets to be about 12inches diameter, that's when
they're going to start producingflowers typically. So it's more
the size than the age of theplant that you're gonna use to

(01:55):
predict when they're going tostart flowering. Regardless of
how long it takes diesel plants,to do this, when they've
acquired enough energy, they'regonna produce a pretty large
flower stock. It can be sevenplus feet tall, and prickly.
They're gonna have spines andstuff along, that flower stock.
Plants will also produce largeprickly leaves along the stems
of the plants as well. The stemleaves of common teasel are

(02:17):
gonna be appear similar to therosette leaves, but they're
gonna be smaller. They're goingto be opposite on that stem, and
they're gonna have spines on theunderside of the midrib, while
cut leaf is going to have deeplylobed leaves and they will still
have those spines on theunderside of the midrib of the
leaf as well. While the plantsonly flower once, each plant
can't produce multiple flowerheads.
Cut leaf diesels is usuallygoing to produce white flowers,

(02:39):
they're going to bloom typicallyfrom July through September,
while as common teasel, it'stypically going to produce
purple flowers, and they'regonna bloom from June to
October. And these flowers thatare kind of small and clumped
and dense oval shaped spikyheads, and a single plant is
gonna be capable of producingthousands of seeds. After the
seeds are produced, the stemsare going to turn brown, and

(03:01):
they may remain standingthroughout the winter, which is
which is when they really kindof pop out in the landscape,
these dead stems standing therealong the road sides. Teasel is
going to grow in open sunnyareas, and they can tolerate
both wet and dry conditions. Andwhile we can find them in kind
of well established high qualityhabitats, we most commonly see
them in disturbed areas likeroadsides, areas where we've had

(03:23):
a lot of construction, thingslike that, because they're gonna
have this open area that theseseeds really need to germinate.
So how did teasel get here?Teasel is native to Europe,
Asia, and North Africa. Andteasel was introduced into North
America in the seventeenhundreds, and was used in the
textile industry, and as anornamental. So for hundreds of
years, the seed heads of tislelhave been used to raise the nap

(03:44):
of cloth. Teasing was the commonname, and this teasing helps
bring loose fibers to thesurface, and it kinda it can
make cloth feel softer.
But we don't use tisel anymorein any kind of industrial
production for this purposeanymore. The dried seed heads
are also commonly used in flowerarrangements, and it could be
one reason why we often findthese colonies around

(04:05):
cemeteries, because of bouquetsthat people have put out at
grave sites. And they also arecommonly used in craft projects
and things like that. Teasel islisted as an invasive species in
Illinois through the IllinoisExotic Weed Act, which means it
cannot legally be bought, sold,or distributed in Illinois. So
despite being able to buy theseed heads online, legally, you

(04:27):
can't do that in Illinois.
So like I mentioned earlier,teasels can outcompete a lot of
our native plant species andthey because they are aggressive
plants, and cut leaf teasel ismore aggressive, than common
teasel. And they're gonna theycan they're capable of rapidly
spreading and outcompeting thesenative plants. The the thousands
of seeds that these plantsproduce, can remain viable for

(04:47):
at least two years in the soil,and this can lead to really
dense patches of plants thatmake it difficult for other
species to survive basicallybecause they just choke
everything else out. And theseeds typically don't disperse
very far. About 98% of seeds aregonna germinate within 14 and a
half feet of the parent plant.
But the plants growing alonghighways and interstates can be

(05:09):
spread further by passingvehicles, you know, that wind
going by, or by mowingequipment, depending on what
times these plants are beingmowed. As the the plants are
being mowed and that's beingdischarged, that can spread at
further distances. Seeds canalso be spread by birds, and
water. Seeds can survive acouple weeks, floating on water,
so they can move that way inditches, streams, rivers,

(05:32):
etcetera. In addition to theirprolific seed production,
there's not a whole lot thatfeeds on teasel here in
Illinois.
So once they get established,there's not much feeding on them
and that just kind ofperpetuates the problems that
they cause. Fortunately, thereare several things we can do to
manage teasel if you have themin a landscape. So the rosette

(05:53):
stage can be dug up from theground. This is gonna be easier
on smaller rosettes because thethe taproot isn't going to be as
large. So if you dig up theplants, try to remove as much of
that taproot as possible, kindalike dandelions.
The more you can get out, theless likely that plant is to
come back. When you have reallylarge rosettes, when they have
that two foot long taproot, it'sgonna be difficult to get all of

(06:15):
that taproot out. Once theplants begin to flower, the seed
heads can be cut off and bagged,and the roots can be chopped one
to two inches below the soilsurface. If this is done,
typically those plants aren'tgoing to come back. If when you
are cutting off that the flowerhead, make sure remove and
dispose of flower heads.
Don't just drop them on theground. Seeds will continue to

(06:36):
develop even after that flowerhead has been cut off the plant.
So get that out of there anddispose of it in in yard waste
or something like that. Mowingteasel, unfortunately, is not a
very effective way tomanagement. The plants will
still produce flowers even afterrepeated mowing.
They'll just produce very shortflower socks there. And because
these are growing as rosette,more than likely the the mower

(06:58):
blades aren't going to hit thoseto begin with. And if you remove
that flower head before itstarts blooming, it's just going
to send up a new one. Sorepeated cuttings, you're just
going to get short flowers onthose. Fire is not particularly
effective either, and this canactually cause a flush of
growth, from that seed bankthat's in the soil.
Remember, they need open sunnyconditions, and by burning,

(07:20):
you've just created that, so alot of these seeds that are
sitting in the soil, all thatvegetation has been removed, and
you get a flush of growth fromthose seeds that are in the
soil. Burning in the fall canhelp sometimes though, because
it can help expose the rosettesthat may be a little more
difficult to see. And then youcan go back with with an
herbicide and target thoserosettes. But burning alone

(07:41):
isn't going to be very effectiveat managing teasel. You're gonna
have to follow it up withherbicides or manual removal
after you burn.
Tiesil can be managed usingherbicides. So typically
herbicides containing glyphosatetwo four d or trichlopyr can be
applied to the plants in therosette stage, this the spring,
early summer, fall. It's goingto be the rosette stage. The

(08:03):
plants begin to flower, theseherbicides become less effective
and aren't very effective atall. So make sure you're
targeting these plants in thethe rosette stage.
Once they start flowering,you're better off cutting off
those flower heads, baggingthose up, and disposing of them.
If you are going to useherbicides, make sure you read
and follow all the labeldirections. That's all I've got

(08:27):
for this week's Garden Mite.Hopefully, you've learned a
little bit about teasel and howwe can manage it in our
landscapes. Good Growing podcastis a production of University of
Illinois Extension.
Listeners, thank you for doingwhat you do best, and that is
listening, or if you're watchingus on YouTube watching. And as
always, keep on growing.