I have placed well over 100 cedars over the course of 15 years when in my twenties and thirties. All them to attract crappie in the water off my dock on a municipal lake. In conversations with an old-timer I was advised not to sink them with green foliage. He recommended to cut and allow the foliage to brown. Then the foliage can quickly be burned off before sinking them. He claimed that crappie would use them sooner that way. I followed his advice and had good results.
The depth off my dock where I sank them was between 14 and 25 feet deep. A cast was required to reach the brush. The brush served to attract crappie particularly through winter and pre-spawn. It's amazing how densely they will pack into brush. I as well as many friends caught insane numbers of crappie from February to Mid-April off my dock casting to these brush piles. Then they would leave to spawn. I would catch them in weed beds while they spawned in depths of 3 to 6 feet. I would just ride the boat on the weeds which held the boat in place while I daubed a jig through openings in the weeds. They would pack densely in the weed beds much like eshupp described. They do like cover when spawning but also spawn communally it would seem.
Post spawn through Fall I would catch them in open water trolling a sassy shad jigs two to a line. It is possible to catch 4 at time when passing through a school. Once you find a school the challenge then is to keep track of them. During the same period, I caught them after dark from my dock using light to attract hexagenia mayflies and also attract the crappie. There is nothing a crappie like better than a jig tipped with a fat mayfly
The summer crappie always seems to be suspended at depths at or above thermocline (in this lake around 12 feet).
It might be important that the species was white crappie and not black crappie.
As for brush. My impression was that it serves more as a resting place for crappie that is most important during cool weather. In warmer weather they range and graze the open water for foraging though likely use brush above the thermocline to rest between foraging forays.
Pat, per your situation of not getting BCP YOY. I am not sure there is way to singly benefit the BCP reproduction. You have a very diverse mix of great fish in your BOW and some occupy space the BCP might fill if only they could. I think I would focus on harvesting those fish that compete most with the BCP.
From the perspective of singly benefitting BCP ... I once read a paper on BCP recruitment that was authored by biologists in Minnesota. They found that rotifer abundance at some time relative to spawn was important to recruitment success. I don't know ... but perhaps a well timed fertilization could help.
