Plum Trees

Store bought plums are picked prematurely so they ship well, but cannot compare in taste to plums picked ripe off a tree. This why we grow our own.

There are four types of plums: American, European, Japanese and Hybrid (Japanese x American).

There are some issues with plums. 

Japanese plums are generally too frost sensitive for our area and most years you will not get plums - spring frosts will kill the buds.

In fact, in 2019 I was fed-up and cut down all our Japanese plum trees. In the past 10 years, they only fruited twice. I have some European and Hybrid (Japanese x American) plum trees on order and will plant them in April 2020.

This will require patience since plums bear fruit in 4 to 7 years when self-rooted and 2-3 years when grafted onto some (not all) rootstocks.

European plums are hardy but usually get infected with the fungal disease 'Black Knot'. There are some exceptions that are resistant like, 'Bluebyrd', 'Early Italian', 'Mount Royal', 'NY9', and 'President'. Of these "President' is the most resistant. You may have heard of the 'Stanley' plum - it is the most popular European plum, but it is highly susceptible to Black Knot.

Removing infected branches as soon as you notice Black Knot is the most effective measure - prune off 6" beyond any black gummy infected areas. If you allow it to spread, it can kill the tree. See the photo below.

European plums are self-fertile, and one tree will produce fruit - however, yield will increase if two or more different varieties of European plum trees are present. 

American plums (Prunus americana from the USA and Prunus nigra from Canada ) are hardy, usually scrappy bushes or trees that produce somewhat tart plums. However, they are great pollinators for Hybrid plums and should be planted along with your Hybrids.

Hybrid Plums combine the hardiness and disease resistance of American plums with the larger size and better taste of Japanese plums.

Hybrids (and American and European) will produce plums in colder areas like ours however hybrids often have sterile pollen. So, there are "pollination issues" with Hybrid plums.

The solution is to have a few good pollinators among your Hybrid plum trees. Also place plums trees close together - only 3 to 6 feet apart, in a cluster, so the branches intermingle. Good pollinators for Hybrid plums are Prunus americana, Prunus nigra, 'La Crescent', 'Pamela', 'South Dakota',  'Toka', and 'Underwood'. Plant at least 1 good pollinator for every 3-4 Hybrid plum trees.

For Plum trees, the best rootstock is Krymsk 1 (Cherry) - mature height is 6-10 feet, produces fruit early (2-3 years), and it increases the size of the fruit. Or grow the standard trees without a grafted rootstock. Myrobalan and peach are very popular rootstocks for plums but Cornell University has found these make the European plums susceptible to 'Brown Line Decline' from 'Tomato Ringspot virus' resulting in high tree loses. There are other rootstocks as well you can investigate.

Good sources for Plum Trees are:
Self-rooted at Fedco Seeds, Maine 
Grafted at Cummins Nursery, Ithaca, NY 
Grafted at Orange Pippen Nursery, Ithaca, NY 
Source for Bluebyrd and NY9, Adams County Nursery, PA 
One Green World, Oregon 
Raintree Nursery, Washington 
Perfect Circle Farm, Vermont 
Specializes in disease-resistant trees at Turkey Creek Trees, Kansas 
Twisted Tree Farm, Spencer, NY (near Ithaca) 
Wallace Woodstock Nursery, Wisconsin 

Below are plums we either have, or are on order for planting in 2020.

The photo on the left from Twisted Tree Farm shows a severe case of Black Knot fungus infection of a European plum tree.

Plum trees need to be checked periodically and any Black Knot and pruned away 6" beyond the site of infection.

In the winter, when there are no leaves, it is easiest to spot. If let go, it can spread and even kill the tree.

When making a selection of  European plum trees, pick ones that have some resistance to Black Knot like 'Bluebyrd', 'Early Italian', 'Mount Royal', 'NY9', and 'President'.

American and Hybrid are much more resistant than European, but can still get infected.
​

American Plums

As said above, Hybrid plums are often sterile, so you need a pollinator. American plums (Prunus americana and Prunus nigra) are excellent pollinators for Hybrid plums because their genes are compatible, and they have a long overlapping period of blossoming. Some specific Hybrids are also good pollinators for specific hybrids like 'La Crescent', 'Pamela', 'South Dakota',  'Toka', and 'Underwood'. Plant at least 1 good pollinator for every 3-4 Hybrid plum trees.

Also, you need bees and other insects for pollination. The pollen is, for the most part, not windblown, so you need help from your friendly insect neighbors.​ Plums bloom too early and the nectar is not sufficiently sweet enough to be attractive to honey bees, so for the most part, solitary bees and tiny wasps do the pollination.

European Plums

European plums cannot be pollinated by American nor Hybrid plums. They need another European plum. Although some European plums are "self-fertile" they have higher production in the presence of another European plum tree that blossoms at the same time.

Hybrid Plums (Japanese x American)

Hybrid plums are more hardy than Japanese plums. On our site, Japanese plums have not done well. In most years, the buds are killed by our unpredictable frosts. In the past 10 years we only had two good years of Japanese plums. So, in 2019, I cut down all the Japanese plum trees and am replacing them with Hybrid plum trees in Spring 2020. Hopefully these will do much better, but we will need to wait a few years to see.

​​"Japanese plums" originated on the Yangtze River in South China and were later introduced to Japan, Korea, Taiwan and Vietnam. So, for accuracy, the current trend is to call them Asian plums rather than Japanese plums - though the term Japanese plums is still widely used.

Again, Hybrids need good pollinators - both compatible plum trees and, of course, bees.