The weather has continued to be dominated by the cold air from mid europe in the first half of January 2010. Snow has remained on the ground for long periods in this part of Kent. Work at Iris of Sissinghurst has stopped for any external ground work in the stock beds. The daytime temperatures have hovered around freezing point so only occasional days, even in the tunnels, have been available to work on the under cover plants. This has included some work on removing old leaves (still acting as host for some green fly) and subsequent spraying for vine weevils in the potted sibiricas when the temperature has been acceptable. Vine weevils are not interested in bearded iris because the root systems are not a suitable host but sibirica, versicolors, ensata’s etc are attractive to vine weevils in pots as well as in the ground so regular treatment is strongly recommended.
The plants under cover have experienced very little rot because the watering regime is controlled. Iris lovers are recommended to regularly inspect their iris in the garden for signs of rot during winter months. The risk of rot is increased when the rhizomes become covered by surrounding earth or even autumn falling leaves. Gentle touching of the rhizome will identify any softening of the tissue – a sure sign of rot damage. Rot can be cut out in the early stages provided it has not advanced too much. Iris are very hardy plants and can survive a degree of careful surgery but of course the cause of the rot needs to be tackled. Grit around the plant, allowing any surface water to disperse quickly, always helps, particularly on clay or other similiar soils.