Vic -- Iris tridentata

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To:       Dennis in Cincinnati

            Ken Walker

            Rodney Barton

Robt R. Pries

And all interested in I. tridentata

 

There have been several questions relative to and comments on how to grow tridentata.  I grow mine in plastic tubs with no drainage, i.e., in mini-bogs.  I try to keep approximately an inch or so of water over the soil surface.  Mine bloom every year under this type of bog conditions.  They appear to me to be very tough plants and will survive under very adverse conditions; however, bloom will be greatly reduced or nonexistent.   I don?t believe that the type of soil is critical as long it is not alkaline.  I wonder if the lack of water, i.e., not growing them under bog conditions may be why some of you are not getting abundant blooms.   Remember, that in the wild, tridentata are bog plants, at least the tridentata occurring in areas that drain into the Gulf of Mexico.  I am not familiar with plants growing in areas draining into the Atlantic Ocean.

 

It may be worthwhile to consider the grow cycle of tridentata.  In the late summer, fall and early winter the mature rhizomes will produce relatively thin stolons from a few inches to 12 or more inches in length, at the end of which will develop a rhizome with a small fan of leaves.  A habit, totally unlike that possessed by any Louisiana Iris species that I am familiar with or for that matter I. virginica or I. pseudacorus.  The leaves on the mature rhizomes at this stage will be from ~20 to ~25 inches in length.  As winter develops the leaves will become much shorter and in many of the clones will eventually have only small fans of leaves, an inch or so in length, and some will go completely dormant with no top growth evident at all.  In late spring the leaves will elongate and blooming here will occur in May and sometimes continue to early June.  Most of the Louisiana type irises will have finished blooming by the time tridentata blooming commences.   In as far as I can ascertain, the new fans produced in the fall will not bloom the first year even though they may appear to be mature.  The tridentata plants remain in active growth throughout the summer.  Tridentata?s growth cycle seem to be the exact opposite of the Louisiana irises, i.e., the Louisiana irises are in active growth when the tridentata are not in active growth or are dormant and when the tridentata are in active growth, the Louisiana irises are not in active growth and may be semi-dormant.

 

I postulate that if the tridentata is kept too dry during the summer, most of the young fans may not built up sufficient reserves of energy to bloom the next year and may need an additional year or years to build up sufficient reserves.  Could this or something similar explain the sparse number of blooms some of your tridentata are producing?  The above growth cycle description is also why I guessed that tridentata should be relatively cold hardy.  Some of that cycle appears, at least to me, to be adaptations for cold hardness.  It also may raises questions as to tridentata?s evolutionary history.

 

The above also partially explains why I have a difficult time believing that tridentata is related to the Louisiana irises.  I would suggest that the fact that tridentata seeds and Louisiana iris seeds are somewhat similar, may only be a parallel adaptation for utilizing the same method of seed dispersal.  Both of these irises occur in wet areas where the dispersal of seeds by water is common for many different kinds of plants.

 

Ken, I apologize for not having a good set of pictures to forward to the forum.  I am very negligent in picture taking and I know I promised that I would get a good set of pictures last spring.  My only excuse is that I got very busy testifying as an expert witness in some environmental lawsuits and did not get around to it.  I intent to rectify that next spring.

 

Ken stated that he has more than a dozen seedlings from the seeds I contributed last year.  I am curious as to how Ken handled the seeds and what was the approximate germination rate?

 

Vic