Re: TB: Mariah/Mulch
In a message dated 12/20/2002 8:03:43 PM Central Standard Time,
> I would like a little clarification please. Are you saying:
> You mulch on top of the iris rzs? All year long?
> Are you saying that the current lore (to not mulch at least during
> spring and summer) is not valid?
Checking some records the following is an accurate account of iris rhizomes
covered with mulch here that support the Morrison Research Project
In 1995 the following irises were planted and mulched over the top with
course pine bark.
Bed FCB 1
Bed FCB 2
Blue Chip Pink
Honky Tonk Blues
Each of the two beds were mulched over the top each year, more or less, as
required with the same course pine bark.
Malaguena died following the first bloom season from soft rot. Snowbrook also
died at some point between 1995 and 2000. I do not know the cause. Champagne
Elegance and Sky Hooks were doing particularly well and were removed from the
beds in 2000 as part of a donation to the Region 24 Spring Regional. FYI:
Malaguena died once more here before I gave up.
9/14/2000 the plants in bed FCB 1 were moved and replanted according to
conventional wisdom (details available). Additionally, Jessie's Song and
Mariah were removed from Bed FCB 2. Jessie's Song was replanted in a
clay/gravel mix were it does well to this day and Mariah was replanted in a
heavy clay. A rhizome of Mariah was also left in the bark mulched bed.
All plants not removed from bed FCB 2 are still mulched periodically with
pine bark over the top. To date no rot has been observed. Increase is however
somewhat retarded. I deem this to be from lack of sun. The bed receives
approximately half sun.
In the spring of 2002 Proud Tradition, though an early bloomer here, began
bloom uncharacteristically early. Examination showed it had contracted soft
rot under it's new growing conditions. No action was taken. It no longer
lives. All other plants transplanted from Bed FCB 1 survive today.
Initially, mulching of beds FCB 1 and FCB 2 was done from a lack of
knowledge. As I gained knowledge (conventional wisdom) and acquired more
expensive irises I discontinued the mulching practice. Curiosity and disdain
for weed pulling did however force me to continue the practice in these two
beds since it was doing no apparent harm.
Now, after reading the Morrison data (pine straw mulch) and in light of my
experience with these two beds and pine bark mulch, I am reexamining some of
the conventional wisdom I had previously accepted as fact relative to irises
and mulch. I am not recommending my horticultural practices to anyone. It's
much safer to parrot what conventional wisdom suggest. It should be noted
that climatic conditions here are significantly different from those from
were most conventional wisdom appears to emanate. The Morrison Research
Project, to the best of my limited knowledge is the only controlled study to
ever address iris issues in the southern portion of the US. It also implies
that conventional wisdom concerning fertilizers might bare some
reexamination, though I suspect some more timely controlled studies in this
area may be available.
It is not my intent to belittle either conventional wisdom or garden lore. My
intent is to point out the need for controlled study of iris issues that
produce definitive answers and to share what I believe to be factual
information others have been generous enough to share with me.
For my climate current lore is now suspect relative to mulch, but not
necessarily deemed invalid. The Morrison data does not record mulch being
removed other than by natural phenomena (wind, etc.) and implies that plants
remained mulched year round.
As a side note, I have on occasion had irises grow upright rhizomes when
mulched heavily. I don't know whether that's from them being left in the dark
or because I keep looking for the light.
Old South Iris Society
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