It's measured by conductivity of a soil sample in water. You can buy a conductivity meter. They are easy to use and I'm sure relaitively inexpensive.
-----Original Message-----
From: Patrick O'Connor
Sent: Jan 28, 2013 7:27 PM
To: iris-species@yahoogroups.com
Subject: RE: [iris-species] Louisianas
Vic,
Many thanks for your response and information. I think you are right about salt buildup. I wonder how one could test for that. Iâm not sure it is part of the standard Extension Service analysis.
One reason that I am switching to shallower containers is that there is better flushing than in a half barrel. With normal evaporation and watering, I hope that salts will tend to be washed away. I will say that even where there is a âdead zoneâ below 8 inches in a barrel, the irises often bloom well. There are some exceptions, though; in a few barrels the bloom and the multiplication declines over time.
I have used inexpensive granular fertilizers also and canât really say I have notice a big difference in growth as compared to Osmocote. I really think that when growing in water, much less fertilizer of any kind is needed. I am using less Osmocote than I used to. I may experiment with high nitrogen fertilizer on the same basis as you mentioned. I know that nitrogen leaches out of soil where there can be drainage, but I have never understood if âleachingâ meant that the nitrogen ran out or if it was just not long lasting in the soilâs chemistry.
Patrick
From: iris-species@yahoogroups.com [mailto:iris-species@yahoogroups.com] On Behalf Of Victor W. Lambou
Sent: Wednesday, January 23, 2013 6:26 PM
To: iris-species@yahoogroups.com
Subject: RE: [iris-species] Louisianas
Patrick,
You stated that you were interested in how I have fertilized irises in drainless containers. My normal procedure is in late winter or spring to add to the 18-gallon containers  cub of 10-10-10 fertilizer. I fill my drainless containers with a top soil that I buy locally by the truck load. It is a black sandy soil with a very high organic content and is slightly acidic. When fertilizing, because of the nature of the soil that I use, I am most concerned with the addition of nitrogen. The soil I use has a fairly good supply of phosphorus and potassium compounds. Phosphorus and potassium compounds in soil do not move as readily as nitrogen and do not readily volatilize. Nitrogen is different. Many nitrogen compounds move readily, leach readily and volatilizes. On occasions, when I didnât have any 10-10-10 fertilizer or could obtain the nitrogen in some other formulation much cheaper (e.g., a 34-0-0 or 29-2-5 fertilizer), I have used the other formulations with the amount applied to the pots adjusted to be approximately equivalent to the same amount of nitrogen that I use with 10-10-10. Undoubtedly, using Osmoscote fertilizer will work very well and since it is slow release it will stay around for a long time. However, since leaching in drainless containers is minimized, I opt to go the cheaper route. Under the conditions that I am growing irises, I would recommend using the less expensive fertilizers. In my experience, it works just as well. If one has questions about major or trace constitutions in the potting soil one is using or is the containers, I strongly recommend that they bring or spend a sample to an Agricultural Extension Office for analysis and recommendations.
I donât understand why your iris roots do not go deeper than 6 or 8 inches in your containers. However, I would give big odds that it is not because of lack of oxygen, since the roots of Louisiana irises grow readily in oxygen poor soil as long as the leaves are exposed to the atmosphere and can transport oxygen to the roots. And, if you keep water over the soil surface in the containers for any significant amount of time, the soil water is going to devoid of free oxygen in both the upper 6-8 inches and the deeper areas. A salt buildup is a possibility. Is it possible that you have a salt buildup because you are applying excessive amounts of fertilizer combined with the possibility that the soil you are using already has a high salt content, and/or the water you are adding to the containers has a high salt content? Since leaching is minimized in drainless containers, less fertilizer should be needed.
Vic
I
From: i*@yahoogroups.com [i*@yahoogroups.com] On Behalf Of Patrick O'Connor
Sent: Saturday, January 19, 2013 6:18 PM
To: i*@yahoogroups.com
Subject: RE: [iris-species] Louisianas
Hello, Vic. I was interested in how you have fertilized your irises in drainless containers. I have grown Louisianas that way for years but have never been sure how to translate fertilizer recommendations for garden plantings into rates to apply in a container when water canât drain through. SLI literature going way back recommends of 8-10 pounds of 8-8-8 per 100 square feet of iris beds, or the equivalent. But I have no idea what happens to the components of the fertilizer in containers such as yours and the ones I use.
In my case I have used large half-barrels, but am switching to shallow pans a bit bigger than yours. I have generally fertilized twice a year with Osmocote and the irises seem happy, but I really donât know what is going on chemically. Nor do I really know how much fertilizer to use. I sprinkle it in at about the rate that I would in a pot of comparable size with a drain hole, or perhaps a bit less than that. Nutrients canât literally leach out, but I still am not sure what is available to the plant. And I worry about over fertilizing.
I have noticed in some of the big barrels that the growth rate declines after three or so years. When digging the irises out, it is clear that below about 6-8 inches, there is a sort of dead zone, meaning that roots donât go deeper. In a more recently prepared barrel, that is not true. Perhaps this is the effect of salt buildup or the lack of oxygen. Maybe I am over fertilizing. Clearly, the best practice would be to empty and remake the barrels every three years, which I try to do, but I donât always have enough time.
I do think that one advantage of shallower containers will be that they do get more flushing from rainwater, as you said.
I would be interested in any thoughts on how to fertilize Louisianas in drainless containers.
Patrick OâConnor
New Orleans
From: i*@yahoogroups.com [i*@yahoogroups.com] On Behalf Of Victor W. Lambou
Sent: Saturday, January 19, 2013 9:41 AM
To: i*@yahoogroups.com
Subject: RE: [iris-species] Louisianas
Mark,
You asked has anyone tried growing Louisiana Irises in containers and did it work without them destroying the container? I grow Louisiana irises (Iris brevicaulis, I. fulva, I. giganticaerulea, I. hexagona, I. nelsonii & hybrids and clones), I. virginica, I. tridentata, I. versicolor, I. laevigata, & I. pseudacorus in containers. I use mainly 20â x 13â x 12 Ââ deep (18 gallon) rectangular plastic tubs or containers but on occasion use smaller 14â x 12Ââ x 7â deep plastic tubs (10 gallon) and larger 30 gallon plastic tubs. The tubs have no drainage and I attempt to keep several inches of water over the soil surface throughout the year (spring, summer, fall, and winter).
I usually fertilize the pots once a year with a commercial 10-10-10 fertilizer; (except those containing I. tridentata, which receive no fertilizer) but on occasions I have skipped fertilizing some of the pots. I have been asked do I encounter any salt buildup in the pots from the fertilizer. I reside in a high-rainfall area and, I assume, that some flushing out of the tubs occurs during high -rainfall periods. And even during long dry spells, I have not observed any problems with salt buildups in the pots.
I have also been asked do I encounter any problems with mosquitos. My answer to that is yes and no. I find that if I maintain water over the soil surface continuously and not let the soil surface dry out mosquito larvae seem to be almost nonexistent. Let the soil surface dry out and then add water to the containers and they will be full of mosquito larvae. In containers, where I maintain surface water, mosquito predators (dragonfly nymphs, water beetles, etc., etc.) evidently for the most part eliminate the mosquito larvae. And, these predators will rapidly cumulate in the tubs. It is not unusual to observe on a single plant leaf the empty shells of two to four dragonfly nymphs that had metamorphosed into adults. The tubs will at times contain clouds of tadpoles and the serenading of frogs at night is an added bonus. Most mosquito species like temporary water pools and not permanent water bodies to breed.
In far as I can tell I do not have any problem with the irises destroying the containers. After, a number of years I sometimes have a problem with overcrowding. Also, after being out in the garden and the sun for a good number of years (4 or 5 + years), the pots start to become brittle and one does has to careful not bang or hit them too hard with some hard object. But I consider this a minor problem if one is reasonably careful.
Vic
From: i*@yahoogroups.com [i*@yahoogroups.com] On Behalf Of Mark A. Cook
Sent: Thursday, January 17, 2013 8:52 PM
To: i*@yahoogroups.com
Subject: [iris-species] Louisianas
Out of curiosity, has anyone tried growing Louisiana Irises in containers? If so, did it work without them destroying the container?
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