Pros: great piney scent, violet flowers, lovely cascading form
Cons: very sensitive to dampness, fairly sensitive to cold.
Rosemary is an aromatic herb with woody stems and needle-like foliage that blooms in clouds of tiny violet stars for months at a time. The piney-scented foliage is a common cooking herb, and the stems can be used as flavor-enhanced skewers for lamb kebobs.
Irene is of the prostrate or cascading form, and is either the most attractive of the drought-tolerant plants, or the most drought-tolerant of blue-flowering herbs. It tolerates, even prefers thin soils, and can tolerate chalky, sandy, arid areas with the ultimate cool, its blue flowers refusing to bleach out in the sun, and its foliage standing out wonderfully against the silvery foliage of most drought tolerant plants. In extreme drought conditions, the leaves will fold in on themselves, protecting the glossy green fronts, presenting a more needle-like appearance.
What it cannot tolerate are frosts and dampness, and I have found it hard to maintain as a perennial on the east coast, which is generally too humid in summer, and too damply cold in the winter. Planting it in a porous container with a Succulent (high drainage) mix added to the potting soil (avoid the soils with moisture crystals a sure way to encourage root rot in these plants) or at the top of a garden wall or mound will also combat the humidity , but the plant is not frost hardy, so restricted to zones 7 and higher if you want it to grow to its full potential (and with a 3 fall to the cascade, there is a tremendous amount of potential to the plant)
Rosemary is one of those plants that I've never heard of anyone managing to grow from seed - in fact, I can't say I've ever SEEN a Rosemary seed! Irene is a 'patented cultivar' bred for a more ornamental appearance (more flowers over a longer season, if I remember right)
Home Depot's website insists that it carries Irene, but I've never seen it in the Philly Region - but they're fairly week on Xeriscaping plants in general. On the other hand, Park Seeds does a good job with its live plants, and they carry it as a 3" potted live plant that can put on a foot and a half of growth the first year.