When a leaf pushes its way past a developing bud to emerge from the center of the fan, its tip tends to form a slight "hook" that points toward the emerging stalk. Once you've learned what this looks like, you watch for this type of leaf as an indicator of impending bloom - even before the tip of the bloomstalk emerges from the fan or the bulge of the forming bud is obvious. In the photo below, the seedling I've circled is a good example. The bud is already showing, highlighted against the tree trunk. The indicator "hooked" leaf is the one immediately to the left of the bud, with most of the leaf extending upward along the left side of the tree trunk and just its hooked tip showing against the sandy path in the background.

The problem with using shadecloth to protect the iris from the intense desert sun is that it's a tempting hammock for a sleepy old tomcat - and one this size can bring the suspended cover crashing down on baby seedlings. So we built a sleeping platform over his favorite seedling bed, using wire mesh for the bottom and folded shadecloth for a cushion.