Terry Aitken reports on a variagated Louisiana iris in his nursery in Vancouver, Washington and speculates what may have caused this to occur.
We have been growing Louisianas in the Northwest for about 10 or 15 years. We have found that they pose a cultural challenge. Louisianas dearly love heat. The problem in the Northwest is that daytime temperatures can reach up to or above 100 degrees F, but the nighttime temperatures drop into the 50s and 60s. The ground remains relatively cool, and we get slow growth on the Louisianas. In the artificial environment of a greenhouse, we have found that Louisianas, potted up in October or November, can be forced into bloom in February. However, Louisianas kept in the greenhouse all year do not receive enough light to initiate buds. (The greenhouse has one or two layers of shade cloth during the heat of summer.)
About two years ago, we reported in the SLI Newsletter the discovery of a variegated Louisiana in our Louisiana field. In last January's AIS Bulletin, I described it in more detail and included a photo on page 39 (#95-LA-l). The one in bloom had been grown outdoors.
The one not in bloom came out of the greenhouse. This year, we kept a piece in the greenhouse in hopes that we would get more vegetative increase. In spite of aspirin and fertilizer, nothing happened.
During the summer, we moved it back outside but did not realize that it was only getting about one fourth day length of direct sun. Finally in September we moved it into full sun where it immediately responded with new growth. The fan doubled in size by the end of October. Perhaps the heavily variegated foliage is even more sensitive to direct sun than are regular Louisiana irises. In the same AIS January Bulletin, there was an article by John Wieler with the theory that either Surflan or Roundup may induce variegation in seedlings. I suspect that it was a factor in my Louisiana seedling. Adding more fuel to that fire, this fall I found a variegated wild daisy in the seedling patch! I still cannot point a finger at which chemical is responsible.
Editor's Note: This article first appeared in the SLI Newsletter in the Summer 2001 edition.