Re: Warning about invasive grass!

**"Marge Talt" m*@hort.net**

Well, Peter, I've been growing P. 'Moudry' for more than 20 years. 
While it does seed heavily, I have yet to find it many feet from the
parent plant, certainly not more than say 5 or 6 feet away, depending
on which way the flowering heads get mashed down in winter.  It does
want to cover the ground around the parent clumps and needs weeding
in spring if you don't cut off the 'bottle brushes' before they
shatter - something I seldom get around to, so I get to pull out the
babies in spring; not an arduous task, though boring.

I don't doubt that some animal walking through the clumps could carry
off a seed or three, but I have yet to see any animal do this. 
Probably some enthusiastic dog would be the likeliest; don't have one
so don't know, but wild animals and cats don't walk through the
clumps I have in various places in my garden.  Clumps are substantial
and most animals would go around rather than through.  

Plants will flower about 2 years from seed germination.  Seed can
germinate at 68ºF (20ºC), but if they do not within three or four
weeks, then they need a cold stratification at 24-39ºF (-4 to +4ºC)
for two to four weeks, according to Tom Clothier's Seed Germination
Database.  I've not tried sowing seed in a controlled situation for
this one.  I can find no data on the web concerning seed viability,
but I would hazard, from the behavior of my  plants, that it is
relatively short-lived.  Either it germinates the spring / early
summer after it's dropped or it never germinates.  Many grasses have
short seed viability, but I understand there is some variation on the
different species of Pennisetum.  

Situations will differ in different places and, like many plants,
this one can become a problem in the deep south (i.e. Florida) when
planted in moist conditions.  Many plants are over exuberant in the
south that barely hang on in the north, as you know.   So, any
warnings about plant aggressiveness need to be tempered by
location:-)  For those with severe deer depredation problems, this is
one plant they will not touch.

P. 'Moudry' will be unlikely to survive happily in USDA zones colder
than 6, although I have seen it listed as hardy to z 5 by one
nursery.  U of Wisc. did a trial of ornamental grasses in 1995 -
2000, at their Noer Facility (USDA z 4), and most of the P. 'Moudry' 
died, so they put it in their Class 3 - not hardy.  I would expect
that there would be less seeding at the far north end of the plant's
hardiness range because it blooms so late in the season that it might
not be able to ripen before killing frost.  Mine is just coming into
bloom now at the end of September and seeds are generally not ripe
until into November here.   I also find that, while it will grow in
part shade, if it is too shady, the clumps tend to die out in a few
years. 

While I class this plant as one that I certainly would not plant if I
weren't willing to weed out seedlings, I really do not class it as
"invasive" in the true sense of the word.  Any plant that sets viable
seed will try to reproduce itself if given the right conditions - I'd
put our native asters far ahead of P. 'Moudry' in the race to
dominate the world.  I must pull 100 aster seedlings to every P.
'Moudry' seedling in my garden:-)

Personally, I think we, as writers, have to be careful using the word
"invasive".  It gets bandied about a lot these days and often applied
to any plant that seeds freely or covers ground in any way in any
part of the country...sometimes very desirable traits, depending on
your goals and where you garden.   I think we need to be responsible
and inform our readers when a plant is known to be aggressive in any
way in some area, but we need to be very judicious in our use of the
word 'invasive'.

Rather than "invasive", I prefer 'aggressive' or 'robust' or
'rambunctious' for plants that have horticultural value and are worth
having if you are willing to keep an eye on them.  I keep "invasive"
for true thugs like Alliaria petiolata (garlic mustard), Kudzu,
Phytolacca americana (pokeweed), wild grape, Parthenocissus
quinquefolia (Virginia creeper), Glechoma hederacea  (ground ivy -
creeping Charlie), Duchesnea indica and Lonicera  japonica 'Halliana'
(Japanese honeysuckle), to name a few winners of my most unfavorite
weed award. 

I do think it unwise for companies to sell P. 'Moudry' - or any
aggressive plant - without mentioning that it can be aggressive, but
I doubt we'll ever see that happen, esp. considering that it is
propagated and sold by Monrovia, who do not mention any aggressive
seeding qualities in their information about it and who seem to
supply most of the US garden centers and probably those big box
stores.

Marge Talt, zone 7 Maryland
mtalt@hort.net
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----------
> From: Peter Loewer <thewildgardener@earthlink.net>
> 
> Group: Just a warning about a potentially dangerous grass. The only
reason
> I'm writing concerns finding plants for sale this past weekend at
two local
> box stores. It's Pennisetum alopecuroides 'Moudry' [P.
alopecuroides
> 'Viridescens'], or the black-flowering pennisetum. This is a
beautiful grass
> that was not imported from New Zealand and named in honor of a
native tribe,
> nor was it, as rumored, a horticultural form found by the
Cincinnati Parks
> Department (seed actually was came from the Baltimore City
Horticulturist,
> G. Moudry), and while strikingly beautiful, it is extremely
invasive. Upon
> ripening, the bristly seeds attach themselves to people and
animals, not to
> mention the wind, and are soon invading your lawn, your garden,
your
> neighbor's lawn two doors down the street or perennial borders two
or three
> blocks away. This grass is attractive just in growth but when in
flower,
> sporting six-inch black plumes on eighteen-inch stems, it's almost
worth the
> trouble of cutting back those flowering stems before the seeds
mature. And
> that's a job you must do! If you don't--Peter Loewer
> 
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