A few customers have written to us concerned about the lack of new growth on their iris plants this spring.
Yes, it’s been absolutely horrible, very dry and cold as well as far too many hard frosts for my liking and for the iris rhizomes !
What Happens to Cold Damaged Plants?
While many people ask how much cold will kill a plant, the real question should be how much freezing will kill a plant. Freeze damage to plant tissue can be detrimental to plants. A light frost typically doesn’t cause major damage, but these regular hard frosts tend to freeze the water in the plant cells, causing dehydration and damage to cell walls. Then if the plant defrosts too quickly, the leaves and stems are killed.
So here’s my advise;
Protect from Frost overnight
If you are getting regular frosts drape a lightweight fleece fabric over the rhizomes in the evening then remove once the sun is up and the frost has melted. You can leave it over the rhizomes if the temperatures stay cold. This will trap a little warm air round the plants. Once the temperatures increase remove the fleece. Remove the fleece if daytime rain is due, but cover the plants again that evening if there is a frost forecast.
Keep the plants watered, do not let them dry out. Take care not to over water.
Feed your iris. A Blood Fish and Bone fertiliser is best, once a fortnight. Don’t over feed or you will encourage weak growth that will be susceptible to pests and disease.