knuttle...Some interesting reading if you do a search for...who introduced Prunus mume. Will give you answers re when it was introduced into this country. Root using softwood cuttings and rooting hormone. I have not tried rooting it in water but certainly an easy experiment to undertake. Must admit that I am a lazy propagator and mostly use the method I have posted a few times. Do a search on the Propagation Forum for "Toothpick Technique".

The dominant offering in North America is 'Autumnalis Rosea' rather than 'Autumnalis', a distinctly different and less showy variety. Neither is weeping. Both are susceptible to twig die-back in climates where this is prevalent. 'Okame' is essentially worthless in my region for the same reason. Maybe you should visit the Japanese cherry collection at the Brooklyn Botanic Garden and have a look at how different ones appear there. Not all they are growing will be easily found in commerce; some may not be on the market here at this time at all. Otherwise, a small-growing one that you should be able to find offered, with a similar general appearance to 'Autumnalis Rosea' is 'Hally Jolivette'. It is not weeping either. For a smaller-growing, weeping white kind the commonly sold Snow Fountains ('Snofozam') TM would be the expected choice. Pictures on the web site of its introducer the wholesale grower Lake County nursery of Perry, OH show how it can be pruned and trained into some pretty extreme shapes - and still grow acceptably. To avoid the pest and disease problems of Japanese cherry trees choose a modern, dwarf disease-resistant flowering crabapple cultivar instead. Lake County nursery has come up with an entire series of dwarf flowering crabapple cultivars (see their web site); some of these (and those introduced by others) will be fairly easily found on the retail market. Here is a link that might be useful: Brooklyn Botanic Garden: Flowering Cherries at BBG

I agree on the ones that TX said. Salvia regla would be great for the part shade situation. Your winters are mild and sandy feet is what they like.. American beauty berry or any beauty berry. The Mexicans have a turks cap that is much larger and very interesting . also known as Sleeping Hibiscus, Malvaviscus arbors var mexicanus. It is less hardy that the regular turkscap and the larger flowers are pendulous.. . I think it is hardy toZ8b ( -9C- -6C). But I see other people on DG that say they grow it in places colder than Z8b. I also have a pink Turkscap of the hardier variety that is beautiful in the shade. The paler color really pops in the shade and I think the flower is larger. I will look to see if I get seed off of it this summer. I do have salvia regal ,Eupatorum havenense (or whatever they changed it to lately) seed and cow pen daisy (this fall). I didn't know Cowpen was a shade plant. I have it in brutal sun. The E havanense grows here in part shade to brutal sun. In England, It would probably need more sun than shade. There is a person on the Salvia forum that grows an amazing collection and sells salvia seed in England. He/She is really free with his/her knowledge and I bet he/she would know the best salvias for that situation. There are other growers that know a bunch about the different varieties over there. I have a lot of salvia gregii , salvia romeriana seeds that I can collect for you. They do part shade. One perennial that would be great in there would be hydrangea quercifolia. An east Texas native, I think but it is gorgeous with foot long flowers that turn a several colors and great fall color. It also needs sun and shade.I love this plant. Lorepetalum chinense var rub rum AKA Chinese fringe plant.. Many varieties, many sizes. I grew it wit a bit of morning sun. Mine grew to 12' before I sold the house. I was expecting 3'. So much for labels. How do witch hazels do in your neck of the woods.. Chionanthus virginicus ( Fringe tree) might need more sun than what you are asking for but I just love this tree and which I could grow it. It is an understory tree but can grow in shade to full sun in a landscape. A shadeplant I like was Bear's britches, Greek Pattern plant or Acanthus mollis. I understand that it can become a thug in some conditions. I did not find this so. Mahonia , We grow Aesculus pavia var flavesens here ( Texas yellow Buckeye) but any of the Buckeyes would do well in part shade. It likes our "moist" (everything is relative) canyons. There are some gorgeous ones. I love the californian white one. I can get seed for a the Texas one. It is a small multi trunk tree, large bushy shrub. I would not mind getting my hands on a A. glabra var arguta (Texas Buckeye).It can do a dryer brighter hotter situation.

Yoshino and Akebono are beautiful and do well here. Look pretty much the same but they are white flowered, from pink buds, but best of all they're one of the first trees to bloom in spring, starting in March with the flowering plums but are much prettier than the plums. Spreading trees. Kwanzan is the other most common one here in western WA, blooms much later, larger flowers, pink, and burgundy new foliage. The burgundy and pink clash to my eye and the colors are both a bit on the harsh side but I've learned to like them. Beautiful fall foliage color too, big spreading trees. Not pest free but do reasonably well and can live to a huge size in well drained soil. Your sandy soil should drain well enough for cherries if there's no shallow hardpan beneath it but you'll need to add organic matter and fertilize yearly if it's nutrient poor, as sand can be expected to be.