There isn't really a feature here called "Ask Douglas Justice", as Douglas reads all the postings anyway, but Joseph Lin sent Douglas one email with several unrelated questions, and the replies were interesting enough that I'm copying them here, and I wanted a title that indicated that these were educational tidbits and they're not my own. Q: Does any wild (Japanese) flowering cherry with 5 petals produce cherries? Douglas's reply: All wild cherries should produce fruits, but some cherries have a complicated pollination biology. A good example is the sweet cherries. Certain cultivars require pollen from specific cultivars. Bing, for example, requires pollen from cultivars that are cross compatible (such as Van or Rainier). Some cherries are self-compatible (don't need a different pollinizer). Presumably, in a large group of different kinds of flowering cherries (flowering at the same time), we should get at least a few cherries forming.
Sweet cherry is a weed in this region so apparently fruiting is frequent outside of orchards. I certainly have seen this tree with fruits many times myself, both inside and outside of cultivation. And it also apparently crosses readily with seemingly dissimilar bitter cherry as the resulting hybrid Prunus x pugetensis is quite abundant locally. Among Japanese cherries the one I have noticed sporting fruits most often here is 'Snofozam'. Its drooping branches are often rather evenly sprinkled with small black cherries.
We saw tons of cherry fruits on the ornamental cherries in Washington, DC. I don't think I saw any cherry tree that didn't have at least one fruit (well, maybe I missed noticing some), and the ones that are supposed to be 'Somei-yoshino' had lots of fruits. Even the late-flowering cherries had lost all their flowers by the time we were there, last week in April, 2012.
Most Japanese cherry garden cultivars are double-flowered (extra petals replacing the sexual parts of the flower), and therefore sterile or nearly sterile. Single-flowered cultivars can produce fruit, but in practice rarely do so in Britain at least, probably for climatic reasons (so I'd not be surprised if the same applied in the PNW). The climate there is much closer to Japan's climate, so better fruiting is perhaps to be expected. Not Japanese, of course; being European, it is better adapted to the similar PNW climate, so again, good fruiting can be expected.
In addition to the consistent general fruiting of 'Snofozam' in this area I have also observed that a collection near here has had multiple seedlings of Prunus pendula come up. And I have seen the P. jamasakura at the Loyal Heights Neighborhood Center in Seattle cover the pavement with fruits, with sheets of seedlings appearing in the bed. But I don't know if this happens most years. I have also noted fruiting of 'Hosokawa-nioi' (A.L. Jacobson provisional identification) in this area. Pretty sure I have seen Yoshino cherries with fruits as well. Jacobson mentions these producing "Small, shiny black, bitter cherries" in Trees of Seattle - Second Edition (2006). About P. verecunda he says "Though the fruit is not choice, it is better than that of Sargent cherry", which bears "Tiny bitter black cherries". Such assessments of flavors would be based on him sampling the output of local trees.
At UBC we have a grove of Prunus serrula in the Winter Garden (two different clones, I think) that occasionally produce abundant crops of cherries. A couple of years ago I collected the cherries and we sowed about a hundred. The seedlings were subsequently lined out in the field and I'm now assessing them for vigor, disease resistance and stem attractiveness. Curiously, a grove of P. sargentii (three seedlings planted together), which flowers well every year despite being in quite a bit of shade, only rarely produce cherries. I don't think I've ever seen more than about a dozen over the whole canopy.
I thought the question was whether these trees ever produce cherries, never mind 100 of them, so I just went looking for any cherries. Here's what I found today: Old 'Somei-yoshino' at the Stanley Park Causeway on the way to the Rose Garden, maybe one per branch, nothing like what we saw in Washington, DC Old 'Akebono' at the Rose Garden, really hard to find Young 'Snow Goose' at Ceperley Meadow - tons of cherries 'Shujaku' near Lost Lagoon, hard to find And double flowering trees: Old 'Accolade' at Chilco minipark, hard to find Old 'Shirotae' at the Japanese Memorial and young 'Shirotae' at Lost Lagoon, not too hard to find
I would wait and survey fully developed fruits later in the year as I think many of the skinny green ones you are seeing now may abort.
Re: White Rock / South Surrey This is funny post about not flowers but fruits of flowering cherries [Edited by wcutler 2012may19: it was only "funny" in the White Rock / South Surrey thread where it was originally posted; I've copied it here where it's right on topic] Snofozam Pandora, I was surprised how small are leaves on Pandora cherry Umineko Shirotae Colt, this tree or bush looks so beautiful with leaves,much better than most flowering cherries after blooming Accolade
Here is (was) a nice cherry on a new 'Rancho' on Davie east of Seymour. It wasn't very tasty - not sweet, not sour, not particularly cherry-tasting, juicy enough but dry mouth-feel. The two cherries I saw on this tree were both on stiff upright stems.
I forgot that we posted so much on this topic, but not for a while. I was surprised to see so many cherries on the 'Kanzan' (double-flowering) trees at Park Royal North. Every tree in this area had fruits. A flower photo was posted by @Orchard at West Vancouver. The cherries were all small, but several were ripe. I tried one - it didn't make me want to try another. The 'Somei-yoshino' a few blocks down my street has tons of cherries, but none within reach.
Pollination is another reason flowering cherries often don't produce fruit. The common variety Yoshino is a very poor pollinator, but may produce if there are other different varieties around flowering at the same time. I've tasted the "cherries" on flowering cherry trees and they are nothing you would want to eat. The fruits are very small, have a very poor flesh to seed ratio, and are a bit bitter, not sweet, and kind of astringent. Japanese flowering cherries are very closely related to sweet cherries though, both of these groups happen to have the same number of chromosomes, and it is possible for them to hybridize together. I was having a conversation with a Chinese person and we speculated that the reason the Chinese never domesticated cherry or apricot was that they already had so many other species of fruits available, whereas in colder Europe there were fewer species, so the population had to focus on domesticating the more limited number of species that could grow there. Chinese did cultivate cherry and apricot but they were the flowering ornamental forms.
Never seen before this year (but I may just be more observant this year) - apparently edible cherries on street planting of Sargentii hybrid trees on 27th Ave. just west of Fraser in Vancouver: I tasted one, and it was not bitter at all - it was sweet, but there was not much flesh on the fruit - too small.
