Further down the block from the curious fruiting pear, there's a trio of raised planters housing a struggling perennial garden. The planters spend the summer under the dense shade of large Sophoras so few perennials thrive there.
However, hosta plants do best in the shade and one guesses that whomever takes care of this garden (maybe they're the same person who planted the pear?), has figured this out -- there are certainly a fair amount of cultivars planted there.
Most hostas are hybrids or cultivars of Hosta plantiginea, H. ventricosa or H. montana. Though the flowers, which are in bloom now, are lovely (and some are fragrant), hostas are sought after for their lush foliage, which varies widely in size, shape and color.
For example, the hosta above looks like 'Blue Angel' (or 'Blue Umbrella' or 'Blue Mammoth' or 'Blue Cadet' or 'Blue Jay'...I could go on), and is clearly cultivated for its color and large leaves. Alternatively, the hosta below is cultivated for its teeny-tiny size and chartreuse hue.
Here's another one, with a clear, jade-green leaf and white flowers.
And another, cultivated for its variegation (most likely this is 'Patriot').
As you can see, the variegated specimen is still leafing out and not nearly as full as the other plants. That can be due to an array of mitigating circumstances (bad soil, cigarette butts, who knows?) but variegated plants also grow more slowly because they have less chlorophyll. Chlorophyll, as you may recall from high school biology, basically runs the show in a plant leaf - on a cellular level. It's key to the process of photosynthesis, the process that produces sugars so that the plant can live and grow. Chlorophyll is also what makes a plant leaf green. So, on the white part of the leaves, there's no (or diminished amounts of) chlorophyll, thus less opportunity for photosynthesis, thus less robust growth.
Hostas are native to Japan and are named for a 19th Century Austrian botanist, Nicolaus Thomas Host. I've read that the young leaves are quite tasty and sold as greens in Japanese grocery stores. I know that deer certainly love them and that slugs will make quick work of a hosta leaf, too.