For the vinaigrette: Segment the tangerines over a bowl, catching any juice for the vinaigrette. Place the segments in a medium bowl. In a small bowl, combine the tangerine juice and zest, Champagne vinegar and lemon juice. While whisking, drizzle in the oil in a steady stream until emulsified. Season to taste with salt and pepper.
For the salad: In a medium bowl, combine the crabmeat, chives and chervil. Add enough vinaigrette to lightly coat, and toss gently. Add the hearts of palm to the bowl with the tangerine segments and add vinaigrette to lightly coat; toss well.
Divide the mache among 4 plates. Place the crabmeat in the center of each plate and arrange the hearts of palm and tangerine segments around the edges. Garnish with edible flowers and lightly drizzle the mache with vinaigrette. Serve immediately.