I'm building a new raised bed for some Oriental lilies and I want to build the very best soil mix I can. I was hoping to get a little input from the folks here.
I feel that some background info regarding my seasons and growing conditions is very important to consider. I live up at Latitude 61 near Anchorage AK. I have a pretty short season. I typically have snow on the ground until May, so I get a late start. It's also very cool by the time Oriental Lilies want to start blooming towards the end of August (temps in the 50's) and into September (even cooler).
My current lily beds all run a soil ph of 6.8-7.0. This works excellent for all my other lilies (Asiatics, OT, LA, AO) and works ok for Orientals. According to everything I have read, the Orientals prefer more acidic soil in the range of PH 5.5-6.5. I'm wondering if the lower PH is needed beacause the Orientals have a real hard time taking up Phosphorus at the higher PH. This seems to be what I see in my Oriental lilies, a slight Phosphorus deficiency in the leaves. This deficiency becomes a little more noticeable as the temps drop. To me that makes sense because plants have an even harder time taking up Phosphorus in cooler temps.
I normally build my soil from leaf mold, compost, small bark nuggets, rock dust/sand and perlite. I was thinking of adding 10% Canadian Sphagnum Peat Moss to my usual mix to bring down the ph a touch.
Does this sound like I'm on the right track?
I love the Oriental lilies and don't mind doing everything right to ensure they do well.
Thx

Sorry i'm no soil expert but sphagnum moss always seems like a good idea. With such a short season plants like lilies with their relatively short bloom times would seem to have a bigger impact on your garden. I'm on Long Island [zone 7] and i'm annoyed my crape myrtles just started to bloom. Need a little more sun i guess.

I think you are on the right track, but I wonder if you really have a phosphorus deficiency. The purpling of lily leaves (if that is what you are basing it on) can be caused by other much more common things. Cool/cold weather is probably the most common reason, but also just general stress from several kinds where the purpling is a precursor to natural leaf senescence (although it may be premature).

Oriental lilies do always prefer an acidic soil. Especially in climates zone 4 and colder, it helps with cold hardiness, too. However, I don't think 10% sphagnum peat will have much effect (but even a small amount is good). I would recommend 25% in your mix, and 40-50% in a clay based soil. It would be pretty unusual if you have a phosphorus deficiency because of higher pH without also deficiencies in other nutrients like iron, magnesium or manganese. You ought to have ample phosphorus from the leaf mold, compost and bark.

@Leftwood thanks for the info. Stress and cold makes lots of sense, it's cool and rains a lot here.
I have plenty of peat moss so 25% works good for me.
Thanks again!