what am I doing wrong?

My Zone 5 yard has clayey soil, amended with an eclectic mix of natural materials and lightly fertilized with bonemeal and manure. We do not use chemicals of any kind. Ph hovers about 6. My hemerocallis, iris, correopsis, delphinia and roses do well but true lilies give me a poor show. Asiatics do not flower at all; Madonnas do nothing after the first year. Other true lilies come up stunted or not at all. What can be the problem?

Poor drainge ? Too much nitrogen rich organic fertilizer ? Manure not composted before applying ? bulbs not planted deep enough ?

Ditto on the poor drainage as a possible cause. Lilies hate to be wet. Have you ever dug up a failed bulb to see if it is rotten? I would look at this as the primary cause of your flower failure.

You might try adding extra potassium which promotes flowering if water is not the cause and cut back on nitrogen as kd suggested. Bone meal has a fairly low potassium content and is higher in phosphate which promotes root development. Manures are typically low in potassium as well. Wood ash has a higher content of potassium (more than Nitrogen and Phospate) or potash is a good source as well.

Hello over there - I'm up in Brighton - always nice to read stuff from other CO folks!
Sorry I can't help with your lilies - my Asiatic does OK here - nothing spectacular though, last year I thought maybe it just needed another year or so to get bigger. Hmmmm, my soil is all sand, amended of course -same as you - sort of with whatever I can find.
My Hems do amazing, and Iris grow well too.
Coreopsis - so, so - they grow, but not very well.
Never had any luck w/ Delphiniums or Roses here, though I am trying another rose this year.
I did put in a ton of Orientals and Asiatics for this year, though, and they're all coming up so we'll see how they do - since climate-wise we're pretty much the same as you. These are all in full sun and will need to be staked since there is no wind protection at all.
Everywhere else I used to live in the Metro area I had to deal w/clay. Bentonite is a dirty word!!
I was thrilled when we got out here 5 years ago and had all this sand!
Good Luck! -Christie

I used to live in Zone 4 Taos, New Mexico. I had tigrinum lilies that did outstanding but any kind of cultivar lilie did so poor I simply gave up. It was not the drainage but the absolutely poor soil quality. The only lilies to ever do well are the tigrinums or 'tiger lilies'.
I think altitude and the intensity of sunlight also effect it.
Michael

Hey, that's good news for me - I did a bunch of Tigers this year!!!
-Christie

Whenever I've had lilies that just were'nt up to par, I've found them to love composted manure. Had some trumpets that were about 3-4' tall with 4 or 5 blooms each, dug them in the fall, worked in a buch of manure, and replanted. The next year they were 6' tall and had over a dozen blooms each and started increasing fast.