Do any of you know anything about the genetic origins of the Shiro Plum or about whether there are multiple strains being passed around under the Shiro name? It seems like I remember seeing it mentioned somewhere that it has a lot of Prunus caricifera in it’s genetic makeup.
Here’s why I’m asking. A FB friend of mine has several mature Shiro plum trees that are doing well for him in Zone 9A Southern Mississippi. It strikes me to be surprising that an Asian plum from the Burbank breeding program would be disease resistant enough to take that sort of climate for very long. Anyway I figured that if it can survive coastal Mississippi that it should be able to take a Georgia 8b climate as well. I grafted two twigs into two branches of a Robusto plum sapling in my orchard. These twigs have since sprouted and are growing well. But the leaves are surprising the heck out of me. They do not look like Asian plum or maribailan plum leaves at all. They look like Chickasaw plum leaves to me. In fact apart from having totally green softwood twigs as opposed to red ones, the shoots are nearly indistinguishable from Robusto and the various improved Chickasaw varieties that I have grafted into this particular Robusto.
I’ve decided to explore whether there is any Chickasaw plum in the pedigree of Shiro. So far I haven’t turned up any information on this one way or the other. But I have found numerous photos of Shiro on the internet. In all cases the plums are canary yellow, but in some of the photos the leaves are long and slender lick Chickasaw plum leaves. In other photos they are oval and more like what you would expect from Prunus salicina or Prunus caricifera. This makes me think that there are two distinct strains out there under the same name with one having a lot of Chickasaw in it’s genome and another (guessing the original) without the Chickasaw genes. I’m just curious what others know about Shiro both with respect to its genetic history and with respect to there being multiple strains. If anyone has any useful anecdotal info on its resistance to disease that would be useful as well.
Also if I should decide to graft Shiro onto it’s own root should I go with an improved Chickasaw rootstock like I would with an Asian type. Or should I treat it more like a cherry plum and graft it onto Mariana. (Not that I have any Mariana suckers left this season.) God bless.
I have seen it reported (in the text here) that it is a combination of Robinson ( P. munsoniana ), myrobalan, and ‘Wickson,’ and a seedling of ‘Wickson.’ On the question of multiple circulating strains, you might contact Rachael Spaeth, garden curator at the Luther Burbank Home and Gardens. I think that she would be interested in your observation and in providing an answer if she can.
IOKOS states that Shiro is part Ussuri plum. Wondering if anyone other sources claim this?
From reports here, Shiro seems to be among the most cold-hardy “pure” (non-P. Americana) Japanese plums. Ussuri blood would explain both the cold-hardiness and yellow color. Also would be typical of a Burbank creation to include multiple unusual plum species.
Back in 2019, what I thought was a Shiro for sure turned out to be something else because it produced red fruit. Two years ago I grafted Shiro into the orchard again, but that tree has not bloomed yet. We shall see, hopefully as soon as next year. As for yours, you won’t know until it produces fruit. Here’s hoping it turns out to be Shiro. Cheers!
I have Shiro grafts that are so old, I forget what member sent them. Have yet to find a cross pollinator that can pollinate it after about 5 years of bountiful blossoms. Maybe this year some of my new grafts will do the honors, same for Ozark Premiere, no way to get it to set fruit so far after five years. I may end grafting these over with productive varieties. This year I have about 40 varieties blossoming so it might be possible to see these fruit.
Dennis
Kent, Wa
Interesting. I’ve heard plenty people complain about Ozark Premiere being hard to pollinize, but I haven’t heard that about Shiro. In fact, there are several threads on here with various people saying how productive but bland it is. What varieties do you have that bloom with it? My guess is that a flatwoods plum will pollinize the heck out of any Asian plum if they bloom together and so would a wild type American or Canada Plum. The catch is that the trees I had access to were killed by a wildfire this winter. Wild type chickasaw plums do a great job pollinizing the Asian X Chickasaw hybrids, but I can’t tell whether they are doing a good job pollinizing the Asian type plums or not. Something in the yard pollinized a big Asian type tree which had poor overlap with other Asian type trees during warm enough weather for bees to fly. It did have good overlap in good weather with a late blooming wild type Chickasaw plum and a Chickasaw cultivar called Sonny’s Yellow which seems to have pollen that seems to work on a couple of other strains but definitely not Byron Gold nor N.C. McKibben.
My AU Rosa and Shiro trees have grafts of AU Producer, Spring Satin plumcot, So Mtn everbeaering plumcot, Beauty, Superior, Alderman, Vic Red American plum.
I am adding a couole grafts of AU Cherry plum to them today.
Hoping that some year some of those will make it thru our late frosts.
Many of those other varieties bloomed this year while Shiro was still blooming.
I heard last spring from a member here that a late frost took the fruit from his plums… but AU Cherry plum did produce fruit. Evidently it is a little more frost hardy than the others.
That is the kind of edge I need here with my late frosts.
Then you should try Lavina and Obilnaja which are very late here and last year took a very hard freeze in bloom, yet produced very good crops. Another one that’s very late for me is the old Luther Burbank variety “Catherine Bunnell”, very hardy blossoms during frost events, precious and productive. All three has had plums every year since the started producing(next year after grafting) four years ago.
“It strikes me to be surprising that an Asian plum from the Burbank breeding program would be disease resistant enough to take that sort of climate for very long.”
Well, my Shiro lasted 12-13 years before the black knot destroyed it. Some trees take time to succumb to whatever the problem is.
Bland here in eastern KS. But Shibumi’s looks identical to mine. The leaves had distinct reddish petioles and midribs. Self-fertile with a heavy crop, usually. Susceptible to brown rot here, I removed it after 20 years of seeing a beautiful crop, only to be attacked and ruined by rot in the last day or two before ripened perfection.
Brown rot is a common theme for any stone fruit. On mine the flavor seems to fluctuate year to year. Some years they are bland while others they are great.
