Re: JAP: CULT: height

Linda inquired:
> Has anyone experienced stunting of Japanese irises as a result of repeated
> freezes during lush spring growth?  The few that managed to bloom (new last
> year, planted in new to irises, presumably acid (everything is unless limed)
> clay, saturated in winter, and staying alternately soggy or moist thru the
> spring) are on little 12 inch stalks. 

Linda, with the informatin you have provided, I would say you have
several things going on with your Japs.  

1. Most importantly, I suspect that you are expecting TB type results
from your Japs. The best thing to do is forget everything you know about
TB's when you start working with Japs & Siberians.

2. Wet conditions without constant cold (frozen!) in the winter can stun
the Japs. The only real danger with freezing and thawing is heaving the
plants. They can and should be planted much deeper than the TB's to keep
this from happening. Mulch is also beneficial. The deeper you plant it,
the slower it will be to emerge in the spring. George Bush has a theory
that late freezes encourage more bud set and can result in a prolonged
bloom time. I posted on that back in the winter. I don't think it can be
tested on first year specimens.

3. Japs can be slow to establish. My experience has been that the
further south you go, the slower they are to establish. I generally get
+40" height by the 2nd or 3rd year in the bog garden. In the mixed
border, with drier conditions, they don't usually grow as tall. There is
no guarantee of bloom the first year on new aquisitions. I only average
around 75%.

4. Don't assume that your pH is correct. Always check it. Japanese iris
can also use more nitrogen than TB's. Don't be afraid to fertilize them
when they are growing. Azelea or holly fertilize will do.

5. When it really gets hot (and dry) Japanese iris go dormant. In the
fall, foliage growth is not obvious, but it does occur. At the same
time, root growth is quite rapid, so another little dose of fertilize in
the early fall doesn't hurt.

Good luck.

R. Dennis Hager
on Delmarva Zone 7B
Where the LA's have just started and the versicolors are charming the
socks off of all visitors.
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