vascular leaf expansion stage vascular leaf unfolding stage A vascular leaf expansion stage during which a vascular leaf participates in the process of unfolding. This stage ends when a leaf is considered unfolded, which varies by species, but generally occurs once the leaf blade has unfolded enough to appear more or less like a small version of the adult leaf. For species with scaled buds, this is generally once the entire leaf blade has emerged from a breaking bud; for conifers, once a needle begins to spread away at an angle from the developing stem or from other needles in a bundle (e.g. pines); for grasses, once the leaf blade unrolls slightly from around the stem and begins to fall away at an angle; for sedges, once the leaf has grown long enough that the two halves of the blade have begun to spread apart like an open book; for rushes, once the exposed, green portion of the leaf has reached a specified length.