Chuck and I went through the horrendous job of transplanting in late August and September. It seems like all our beds came due to be divided at the same time. Chuck prefers to dig up the entire clump after the second year of bloom.
When our irises are transplanted back into newly conditioned beds, he places them 24" apart. Chuck often plants two rhizomes of the same variety behind the other two – each rhizome representing the corner of an imaginary square. Sometimes he even plants them in a triangle as our visitors really like to see a lot of bloom on each variety.
Here in Paradise, our average annual rainfall is 50 inches. Two years ago we received 102 inches of rain. As a result of these tremendous rains, the irises looked terrible; some plants looked worse than others. We were afraid we would lose all my seedlings. Lots of irises are planted in pots here, so in addition to the 5 beds of two year seedlings there were 2400 potted irises also affected.
The center fans turned brown and were soft and slimy. (Judy: see two photos) We phoned Monarch Labs who does our soil testing and talked to a Mr. Barnes (no relation) who is an agronomist. He asked that we bring plants to him for observation.
A few days later we again talked to Mr. Barnes and he diagnosed our problem as “bacterial leaf spot”. He determined that the excessive rainfall had compacted the soil; the irises could not “breathe” and were suffocating. The ph level had dropped dramatically and the soil was very acidic.
He suggested that we buy a product called Foliar Phosphite, instructing Chuck to spray the irises three times at seven day intervals. In three to four weeks the irises were free of the bacteria, they looked great and it was amazing how they snapped out of it. Mr. Barnes also mentioned to Chuck that the “sugars” on the outside of the fans were also affected, but we do not remember the details of that diagnosis.
We called Mr. Barnes several times because we wanted him to write an article for Tall Talk but he never responded to our calls. We later learned that his wife and son were killed in an auto accident, he sold Monarch Labs and has moved away.
Last year Chuck sprayed late in November just as a precautionary measure. This year the irises were free of everything! We had no crown rot at all which is most unusual.
Our rhizomes were also unusually large this year, some so large that they would not fit into gallon pots. We have no way of knowing if this could be the result of the application of Foliar Phosphite. Perhaps the fact that we received only 35 inches of rain was a factor, and we sure hope we never see 102 inches of rain again!
Foliar Phosphite fertilizer is manufactured for Helene Chemical Company, 225 Schilling Boulevard, Suite 300, Collierville, TN 38017 (near Memphis). The label on the container reads: “This product is only for use in Arizona and California.” The solution is 28% Total Phosphoric Acid and 26% soluble potash (derived from potassium hydroxide and phosphorous acid). We use 1 ounce of Foliar Phosphite and 1 ounce of sticker solution per 3 gallons of water. It is rather expensive and the smallest quantity we could buy will last us for a lifetime.
It is our hope that this information might be of use to other bearded iris growers who may experience the frightening attack of bacterial leaf spot in their gardens.