One of the most memorable of the original ‘Star Trek’ episodes
involves an itinerant space peddler who barters for an alcoholic beverage with
a small, fluffy creature called a Tribble, the likes of which no one had ever
seen before. The Tribble likes to be stroked; it coos and makes people feel
good; perhaps
too good. The Tribble’s chief downside is that is fecund
to a fault. In the words, of Dr. McCoy, “Jim, as near as I can tell, these
things are born pregnant.” Tribbles soon overrun the space station and threaten
a shipment of a valuable grain seed stock. I won’t spoil the plot, but at the
end of the episode the Tribbles are dispatched to a Klingon war ship.
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| Perennial ageratum |
I was thinking about that episode yesterday as I spent the
better part of an hour getting rid of my own Tribbles; specifically, pulling
out patches of
Conoclinium coelestinum, better known as perennial
ageratum, from my garden. Thus far I have filled two, 50-gallon cloth barrels with the nasty stuff. I suspect my work is not yet done.
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| 'Good' Ageratum houstonianum |
A quick tutorial:
Ageratum houstonianum, as anyone who
grows summer annuals knows, is a wonderful filler plant for containers and a
great ‘boots and socks’ border for beds. It has a lovely, bluish-purple flower
than draws the eye. Alas, it dies with the first frost. It is a wonderfully
well-behaved annual, prized for that unusual color. I can recommend it unconditionally.
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Note the area circled in blue:
the perennial ageratum was
half the height of the Fothergilla
'Blue Shadow' |
Now, let’s talk about perennial ageratum. While both it and
its annual namesake are members of the aster family, their only common attribute
is their similar-colored flower.
Conoclinium is anything but
well-behaved. It spreads by rhizomes; it spreads by flower seeds. It may even
spread by word of mouth. But, once it is in your garden, controlling it is a
full-time job come the end of summer.
To the best of my knowledge, neither Betty nor I have ever
purchased a pot of perennial ageratum, yet this August it is everywhere in the
garden. It is crowding out our beautiful Astilbe, upstaging our Fothergilla,
and colonizing a bed of spring bulbs that, without human intervention, would be
suffocated by a mat of roots. How did it get here? Maybe an itinerant peddler
traded a sprig if it to one of our neighbors for an alcoholic beverage.
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This false strawberry ground cover was
engulfed by perennial ageratum. Time
will tell if I got it all. |
What I do know is it has to go. But the
Conoclinium has
its own plan. Pulling it out is a piece of cake: it appears to come out with
its roots intact. But, if you pull out a stand and then sift the soil, you’ll
find pieces of roots and rhizomes cleverly left behind. I found that out
because I thought I had completely eradicated perennial ageratum from the top
of our driveway bed. Three weeks later, there were hundreds of replacement stalk
coming into flower. (The plant apparently thrives in rain, of which we have more
than our share.)
Now, whenever I remove
a patch of
Conoclinium, I immediately also dig around in the surrounding
soil to see what may have been left behind. I am seldom disappointed.
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Note the perennial ageratum
(circled in blue) hiding in
the Rudbeckia goldstrum |
What is worse, the more I look, the more of it I find. The
plant loves the sun. It also thrives in deep shade. It had insinuated itself in
a bed of
Potentilla indica (false strawberry) where it was keeping a low
profile, as well as in a clump of just-past-bloom
Clethra alnifolia
(summersweet), where it had stretched to a height of four feet. Perennial
ageratum is an ambitious interloper.
As of yesterday, I believe I have, at least for the moment,
gotten it under control. Which is, of
course, a foolish statement. We’ve had two inches of rain in the past 24 hours.
I know darned well the perennial ageratum is using the time to take stock of
where its remaining troops are recovering. Reinforcements will be called in,
perhaps from neighboring properties. I don’t know exactly when this war was
declared. What’s more unsettling is that I don’t know if I’m winning or losing.
