Q. I planted several bulbs of iris in my yard about 7 years ago. They bloomed for many years but the last two years they had no blooms. Is there anything I should be doing? I clean out all the dead leaves between bulbs and have removed a couple of bulbs. They are watered same as other plants according to the time of year for 25 minutes.
A. The usual problem when iris is not blooming when they were when they were younger is not dividing them.
They must be dug up, the rhizomes severed, dusted with a fungicide and left to heal for a day or two in the shade, spaced appropriately and replanted. Throw out damaged or rhizomes that are too small unless you want to baby the small ones until they get enough size to bloom.
Distances apart depend on the size of the iris; smaller ones closer together and larger ones further apart. Taller ones toward the back and shorter ones near the front.
Replant them with compost and a starter fertilizer mixed in such as bone meal. Fertilize once a month lightly with a good quality flower fertilizer.
But overcrowding will cause them to stop blooming. They are in the same spot so I am figuring the light is the same unless some trees got bigger and limited sunlight to them.
For watering a large iris bed I would use low pressure, in-line drip emitters in half inch poly pipe such as Jain or Netafim brands preferably. Space the pipe about 12 inches apart parallel to each other throughout the bed. They can be laid on top of the soil, just under mulch.