Transplanting and Japanese Irises, and regular Irises , delphiniums - Knowledgebase Question

kalamazoo, MI
Question by dfgquilter
August 13, 2009
I've heard that we should wait til Labor Day to start transplanting and another source said that we can start the last two weeks of August. What do you recommend?
I have Japanese Irises that grow and are healthy looking, but have never bloomed. What can I use on them to promote blossoms? Should I dig up and amend the soil too?
Which is the best fertilizer and /or soil for regular Irises?
Also, what should I put on my delphiniums?

Thanks so very very much! ( I have alot to learn!) Dorian

Answer from NGA
August 13, 2009


Mid-August is a great time to dig and divide irises. You can do so all the way up through the middle of September and they will have ample opportunity to settle in before winter arrives. If your Japanese irise are overcrowded or if they are not getting enough sunshine, they can fail to bloom. I'd dig and transplant them. Amend the soil prior to replanting and be sure to give them 4-5 inches of space so the roots won't have to compete for moisture and nutrients. Feed your irises and your delphiniums in the spring with a 10-10-10 general purpose fertilizer (or a 20-20-20, if that's more convenient). Best wishes with your garden!

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