What makes irises not bloom

The fibrous roots should be planted deeply, but the top of the rhizome should be at or slightly below the soil surface. Keep mulch away from the tops of the rhizomes. Look at the size of the rhizome when you plant it; if it is small, it is possibly a young rhizome that needs to grow for a year or two to reach maturity before it is able to flower.

Irises that are too closely planted may not bloom. When putting in new iris rhizomes, place them at 12 to 24 inches apart. Place the end of the rhizome bearing the fan of leaves so that it faces into an empty spot in the bed because the iris will increase its growth in this direction. This gives the plants room to grow over the next two to three years.

After two to four years, the irises become crowded from new growth and can stop blooming. Dig up the clumps and divide them. Replant the divisions, give them away to friends or donate them to your local iris society. Irises need at least six hours of direct sunlight every day to bloom well.

I answered her post with a list of conditions that could be responsible. When bearded irises are planted in the shade, they will often produce only leaves. Make sure they get hours of sunlight per day more is better. The rhizomes are lousy. Bearded iris rizomes should be about a little fatter than your thumb, and firm not mushy.

I would wait until early August weeks after their normal bloom time. When you dig up the irises, use a spading fork instead of a shovel.

The rhizomes might be planted too shallow or too deep. They should be just beneath the surface, so you can sometimes see the tops exposed in a few places. Just cover with an inch of compost or well-rotted wood chips. Which brings us to Reason No. Iris likes loose, well-drained soil. Lack of water in late winter and early spring may also prevent proper growth. To remedy the problem, determine which of the scenarios described above is most likely to fit your situation.

If none seem likely, contact your local Cooperative Extension Service agent who can make a diagnosis after seeing the problem on-site.

It may be a good idea to divide and replant your irises. Find a sunny location receiving at least 6 hours of direct sunlight each day.

Prepare the planting site by digging the soil deeply to loosen compacted soil. As you are turning the soil, add amendments such as compost and a phosphate fertilizer. If you use a complete fertilizer that contains nitrogen, phosphorus and potassium, be sure to select one that has a high phosphorus content the second number of three large numbers on the bag.

You can also use superphosphate or colloidal phosphate. Both of these are sources of only phosphorus no nitrogen of potassium and will not "burn" the plants. If the site chosen is the existing site, remove the iris plants and store them in a shady location until you are ready to replant.