I can give you some help with the beach plum (Prunus maritima) part of your question. This is a subject that I know well and look forward to a book that is being written about the history of and those who have hybridized it. First you should know that beach plums do not set fruit consistently year after year. This has frustrated growers through the years as it is not a dependable crop. There is now a renewed interest in BP's and it is becoming more available in catalogs for the home gardener. Grown inland away from the ocean it forms a pleasing bush shape about 5' high and wide. Those living along the New England coast know it to be a fairly low, wind tossed bush with a major rooting system that often is the 'glue' that hold sand dunes together. As part of a research project we once dug a dune growing BP to study its root structure. Gave up after three days of digging as we never did find the root termination. If you do grow your BP in a container it should be a large one with good drainage set on bricks. Every second year I would probably dig it when dormant and trim the extensive root system. It is a thirsty but very tough shrub as I have found over the years of raising seedlings. Do a search for 'growing beach plums' which may be of further help.

Greetings: I fully realize that this post is too late to help folks in winter 2012, but if your planting plums in the SE USA, and can provide some maintenance, I recommend using hybrids between P angustafolia (Chickasaw Plum) and P. salicacia (Asian plum). These are bread to have the eating quality of an Asian plum but the disease resistance of a Chickasaw plum. Even with these you will have to do some pruning and spraying. There are two series of these, one produced by Auburn University. The Auburn series plums tend to have higher chill requirements and would be better for the upper south. The other major series is the "Byron Series" developed by the agricultural station in Byron GA. These trees have lower chill requirements and are best for the lower south like the coastal plains of GA and AL. There is a third series called the Gulf Series which may be a hybrid with a different wild plum species, but these are good for hardiness zone 9 and higher. Thanks and God bless. PS: I planted 4 varieties of the Byron series and one of the Auburn University series this winter, and so far all the plants are doing great. You can get several members of the AU and Byron Series from Johnson's Nursery out of Ellerjay GA. A couple members of the Byron Series and the Gulf series are available at Just Fruits and Exotics outside of Tallahassee FL.

It is a plum, as bboy said. I am not a botanist so I can't help you with the specific scientific details of why it is. I only know from experience. It just looks like a plum! One thing is the relative sizes of the petals and stamens and another is the bark markings. (Not very helpful, I know.)

Prunus maritima (I assume this is the beach plum you're referring to?) is a suckering and spreading larger shrub-type of woody plant, so it would be best I would think kept away from the foundation of your home, to be safe. They can get up to about 10 feet tall. You can cut back suckering growth yearly in late winter from the base to encourage a trunk to form and thicken if you like the tree form, or let it grow how it will and it'll form a dense mounding shape. The general rule for cross pollination of fruit trees is no more than 100 feet apart for good pollination- the closer the better. I have apple trees on my property that are about that far apart from the big old crab apple that I use for pollination and this works well. Nurseries say 2-3 years after transplant and you can expect a crop, but depending on initial size and health after transplant and all that, it could take a longer or shorter amount of time. These beach plums are a great addition to the landscape for a lot of reasons, so I think you're making a great choice here. Cornell is working on making them more suited to commercial production even, given the quality of fruit these produce and how hardy the species is. Can't argue with the blooms in the early spring either. :) And in case you're interested, the pawpaw is another great edible landscape tree. They get larger than beach plums of course. They're also a native of the US, hardy, healthy, and the fruit is a long time forgotten treat which deserves more recognition. You don't see them in commercial production because pawpaw fruit don't store and ship well- best eaten fresh! They're delicious. Here is a link that might be useful: Pawpaw tree