Plums in Zone 4 midwest: Creating Diverse set of Black Knot Resistant Plums

[ShiverMinneapolisZ4b]

(EDITS: UPDATED BASED ON FORUM FEEDBACK ON 2025-02-07.)

I am trying to create a short list of Zone 4 hardy plums that are Black Knot resistant. (Lots of Black Knot growing on wild, tall Black Cherry trees here.) Yes I know that resistant does not mean immune. After that my next goals are flavor variety first and and a relatively wide harvest time second. I’m not the biggest fan of over-sweet fruit, so Waneta sounds appealing. So I wanted to check if I have a good choices.

My notes below provide a list of some choices along with theoretical harvest dates.

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Plum (Rosaceae \ Prunus xxx)
Genetics are usually Japanese (salicina), European (domestica), American (americana), or Cherry Plum (cerasifera). European are self-fruiting, but Japanese require compatible cross-pollinator. Stanley is the standard in stores. Toka is probably a good base tree.

July harvest:

• Methley: early harvest, don’t keep, not a connoisseur plum but disease resistant, easy. Japanese. Partially Black knot and rust resistant, but GrowingFruit has had BK infections. Jul 13.
• Early Italian: Recommended to me. European. Early Italian type is black knot resistant. July.
• Waneta: not cloyingly sweet unlike newer plums. Japanese x American. Black knot resistant. Late July.
• Sprite: small size. Japanese x cherry plum. Allegedly Black knot resistant. July-Aug.

August harvest:

• Black Ice Plum: U of WI cross of Japanese and cherry plum. Japanese x Cherry plum. Partially Black knot resistant but GrowingFruit growers had infections. Early Aug.
• Toka aka Bubblegum. Spicy and sweet. Good pollinator and very hardy. Japanese. Resistant to black knot. Probably good base tree for multigrafting. Aug 17.
• Superior: U of MN introduction as a cross of the popular Burbank cultivar. Japanese. Resistant to black knot. August.
• Prunus Americana: wild plum tastes sour and astringent, somewhat resistant to black knot. Fedco Seeds (zone 4) recommends as rootstock for owner-grafted plum and peach. Suckering. Good pollinator donor to others but still needs pollinator; pollinates both Superior and Black Ice (Toka also pollinates). Late Aug.
• Alderman: Cold hardy, needs pollinator. Japanese x American. Black knot resistance confirmed by GrowingFruit growers. Aug 22.
• Damson: Originally from Syria, processing not fresh eating. Resistant to black knot. Aug 22.
• Bluebyrd: excellent sugar-acid balance for fresh eating or processing; may be zone 5 only. European. Black knot resistant. Aug 30.

September harvest:

• NY9: Fedco Seeds says fresh eating and processing survives Z4. Forum review says better than Early Italian. European. Very black knot resistant and resistant to other diseases. Early Sept.
• President: Processing plum, survives Z4 Montana. European. Very black knot resistant. Mid Sept.

Two lists of Black Knot resistant plums:

Black knot resistance is present in: President, Bluebyrd, Methley, Milton, Early Italian, Fellenberg, Shiro, Santa Rosa, Shiro, Castleton, Seneca, Damson, Bluefree, NY9, Formosa, and Au Rosa.
Edible plums that are moderately resistant to black knot are ‘Damson’, ‘Bluefree,’ ‘Shiro’, ‘Santa Rosa’ and ‘Formosa.’ Japanese plums are generally less susceptible. ‘President’ is the only type of edible plum that is considered highly resistant.

For my orchard, I am starting with American plum specimens but I might get a Toka. If I wanted a multigraft for variety, my impression is to proceed in this order until I run out of graftable branches: Toka (Japanese), Waneta (Jap x Amer), Sprite or Black Ice (Jap x Cherry P) , NY9 (Euro), Superior (Jap homage to Luther Burbank & U of MN release), Early Italian (for early harvest), and maybe Flavor Grenade plumcot (for variety but unknown disease resistance). But I might replace Toka with Superior as a good pollinator, then insert Alderman.

[ltilton]

My (Euro) Brooks plum was showing Black Knot until I cut down my old Italian Prune, which was full of it. Not seen it sincee.

[jrd51]

Black Knot is endemic here due to the huge population of wild black cherries. So I am trying to limit my trees to those that are immune (or nearly so) to BK.

Among hybrids: My Black Ice exhibited fairly frequent strikes. I concluded that while it may be “resistant” to BK, it is far from immune. I removed it.

Alderman has been free of BK over 8 years. I’m adding LaCrescent, Waneta, Toka, hoping that they will be OK.

Among Europeans, I’ve seen few if any strikes on Kenmore / NY #9, President, and Bluebyrd. I’m adding Empress. I’m not aware of other good choices.

p.s. I tried growing Shiro and a few other Asians at another home many years ago. All of the Asian plums (and sweet cherries) showed the same pattern: Good growth for a few years, some decent crops, then sudden death. I’m not sure of the cause; could be bacterial canker.

[ShiverMinneapolisZ4b]

Thank you, that’s very helpful. I might try Sprite instead of Black Ice as the cherry plum cross. Montana Fruit Company says President can survive Zone 4 and is a late season processing plum and Fedco Seeds says NY9 survives Z4 as fresh eating and processing plum. Not sure about Bluebyrd. Unfortunately searching google already brings up this thread which is less than 24 hours old as the #2 hit.

Experienced gardener in this town says cultivated cherries here like Montmorency exhibit the same death after ~10 years pattern, so I won’t try. Said the disease that kills local cherries wasn’t black knot. I see several people in neighboring town have Contender Peaches (there are few zone 4 peaches).

[jcf]

First of all I commend you for your aspirations. I’ll just chime in with my variety observations.
Im not in your area but I do have very heavy Black Knot pressure on my plums. Here in this area we do have a big population of native “wild” cherries. I never knew there was a connection?
The Japanese plums are my plums of choice that I continue to grow for market and battle Black Knot with. All others I have given up on mostly due to their growth habit being too upright and vigorous making them too hard to closely monitor for Black Knot.
Here are what I have grown over the years. All are Black Knot prone.
Beauty
Shiro
Methley
Imperial Epinouse
Early Laxton
Valor
Seneca
Rosy Gauge

[Cgardener]

I think that Toka, Waneta, and Superior are good choices. Like jrd51 mentioned Alderman is another good choice. Kenmore / NY #9, President, and Bluebyrd are likely better choices than Early Italian for European plums. Some people have noted black knot issues with Methley so might be better to avoid that one (depends on region but multiple people have had problems).

Need opinion on best cold hardy, disease resistant plum

HI Steve. Im in the Lake George area of upstate NY. We used to be zone 4 but now 5 . It gets very cold in this area. I have about a dozen plum trees and have been getting devastated by Black knot . Methley, Bruce, Burbank, Santa Rosa, Black Ice, Hanska, Shiro, and especially Stanley Prune have been overwhelmed and all but two of those are still standing. So far, there is nothing on my Alderman( whiich has large red plumbs in August that taste great) and no sign of any on my Superior that i…

Insect and Disease Identification Thread

Definitely black knot Methley is particularly susceptible

[ShiverMinneapolisZ4b]

Well, there you go. It only took 12 hours to make it to the #1 place on Google.

Suddenly we are the source everyone is going to be referencing.

[ShiverMinneapolisZ4b]

I edited to update my original post based on feedback, for the benefit of those coming to this forum via google search. (Like a conscientious forum member would.)

[ShiverMinneapolisZ4b]

Just curious for the notes I leave: What makes the European plums NY #9, President, and Bluebyrd better than Early Italian? (E.g. flavor, variety of flavor by not being just like a Japanese plum, black knot resistance, productivity, drought tolerance, etc?) The reason I ask is because Early Italian extends the early harvest window by allegedly fruiting before cherry plum crosses. In Zone 4, sometimes you take what you can get. President seems to be the one the most websites claim is highly Black Knot resistant and it extends the harvest on the late end into September, but September is when I have many other things producing.

[Cgardener]

NY #9, President, and Bluebyrd are the European plum varieties that I had seen people having good experience with regarding black knot which had been your biggest priority. These were also the European plums that were indicated as black knot resistant by Purvis Nursery which also offers scions, so I had come across these in my research on the topic of black knot resistant European plums in the past Plums - Purvis Nursery and Orchard.

I had not seen much on the resistance of Early Italian but in researching that further I found that Lonster gave an update in 2024 Tumor/Gall on my pluot tree - #14 by Lonster that suggested that Superior and Alderman are his standouts for resistance (12 years without infection) and Maneta, Early Italian, Toka, and Au Rubrum are younger trees that he has that had avoided infection so far. In the end, it looks like his Bluebyrd and President had knots.

Given what I have seen, Early Italian, NY #9, President, and Bluebyrd are better than average for European plums in the area of black knot resistance but if your pressure is high enough there is a real risk of infection. Other things to consider are that NY #9 is probably a mild flavored plum that is better when dried (per Purvis under name Kenmore) but has good production and some rot resistance, President plum can have brittle wood ( Plum - President - tasting notes, identification, reviews) but is late season and some reports of good flavor, and Bluebyrd was tested in warmer hardiness zones so you are probably right to be concerned about hardiness but has had good reports on flavor.

I think the most resistant varieties like Superior and Alderman are getting the resistance from the American plum genetics and will give you the best results over the long term (note that not all hybrids will have the same amount of resistance but these two seem to have good reports from people who have grown them). The Wisconsin trial has some interesting notes on these varieties along with other hybrids that you were looking at. Japanese-American Hybrid Plums – Uncommon Fruit.

[jrd51]

My understanding is that Empress is a sibling of President, so it should be similar but different. Worth a try, I think.

[ShiverMinneapolisZ4b]

For readers, here’s cross-reference to a 2019 thread, but that one was not limited to zone 4:

Plums and Pluots without black knot

I tend to mention problems with my fruit trees and I think doing so is important but I thought it might be a helpful to start a topic which emphasize the ones without black knot or very low occurrences. Even though I’m pushing no/low black Knot all comments are welcome. In my opinion I think mentioning how long you have had the variety is important. As of now these are the ones without black knot Odom 3-4 year Guthrie 3-4 years AU Cherry Plum 1-2 years AU Rosa less than 1 year Spring Satin…

[tbg9b]

@ShiverMinneapolisZ4b

Well, there you go. It only took 12 hours to make it to the #1 place on Google.

This can be very misleading, because google tracks every site you visit. If you visit a page on growingfruit.org covering a specific topic, and then search google with key words contained on the page you recently visited it is common that google will rank that page highly in your search. The more you visit a website the better the chances are that google will start slanting its search results tailored towards your personal viewing habits.

[ShiverMinneapolisZ4b]

Thanks. I turn off WiFi on my phone so it would use the Cell Phone network, switched to Opera, opened an Incognito tab, and searched for “zone 4 black not resistant plums” on google. This is the top hit.

Also tried searching Bing (I never used) in a Private tab

And Duck Duck Go:

[tbg9b]

So your saying they’re not watching you.

Just kidding.