Thank you for getting back to me. There are several reasons why irises don't bloom. The most common is lack of sunlight, but we have ruled that out. The second most common problem is planting depth. The tubers should be planted so the top is visible at the soil surface. Just because the plants came potted from a nursery doesn't mean they were at the correct depth, so double-check this. If you can't see the tuber at the surface, the plants are too deep. Even that little layer of rock could interfere because the tops of the tubers should be exposed to sun.
If planting depth is fine, we have to look deeper. Soil that is too acidic or alkaline can interfere with blooming (that could also affect tomato growth), but we'd need to know which it is before we could make any changes. If you can't get your soil tested, tell me in which state you live and in what part, and I may be able to get a general idea of the soil's pH.
Too much nitrogen in the soil can lead to good leaf growth, but no flowers. A good fertilizer for irises is 6-10-10. The first number is the nitrogen content. The bone meal you're considering would be a good choice, too, but I wouldn't add any sand. It has no nutrients and would just put something else on top of the tubers.
Poorly drained soil is another culprit. Irises don't do well if the soil they are in stays soggy after rain or watering.
Finally, irises won't bloom if they are crowded. When you bought the plants, they may have formed a clump in the pot. If you planted them that way, they may simply be too crowded to bloom. In general, irises need to be dug up, separated, and replanted every 3-4 years to maintain their vigor.
You're probably wondering what you should do now. If we can, I'd like to try to narrow down the possibilities and then give you some recommendations. Give me the information on your location so we can know at least a little more about the soil. If possible, post a photo of the planting. That would tell me a lot. You can upload a photo by clicking on REPLY, then at the top of the area where you would type is a tool bar with icons. Click on the little paper clip icon (it's right next to the YouTube icon). Instructions will pop up. On some browsers, this doesn't work. if that happens, you can put your photo on one of the free photo sharing websites, such as www.photobucket.com
. Then come back here and paste the link to your picture in a REPLY.
I'll watch for your response and we'll go from there.
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