Posted by shane - January 8, 2015 - A-Z Plant Maintenance, Trees - No Comments

Prunus padus var. cummutata

DCF 1.0

Mayday is extremely common and, not surprisingly, of the of species we prune most frequently.  They are a nice medium-sized shade tree that offers an excellent, scented flower display in Spring.  They are very hardy, and although prone to infection by black knot disease, can still grow vigourously even if heavily infected.  Sadly, too few mayday owners understand the impact of black knot disease.  After many years of neglect, I get the call to assess the tree, and often end up recommending removal because the disease is too advanced to allow for proper pruning.  Mayday is a nice tree to have in the yard, but mature specimens require annual monitoring and pruning for them to look their best.

We don’t include mayday trees in our designs, unless requested, due to their higher than average level of maintenance.



Full sun

Pruning Time

When the leaves are off the tree, from early November until mid-Spring, prior to bud-break.

A heavy infection of black-knot disease in a mayday in Red Deer.  S. LePage photo.

A heavy infection of black-knot disease in a mayday in Red Deer. S. LePage photo.


Prune as a central leader standard as you would a ‘Schubert’ chokecherry of flowering crabapple.  Most mature specimens I encounter have poor structure as a result of insufficient training as young trees.  At planting, subordinate co-dominant leaders and ensure well-spaced scaffold branches along the main trunk.  Reject specimens that have multiple limbs growing from the same point on the main trunk.

Annually, remove dead, diseased, or damaged limbs, and remove major crossing and rubbing branches, or branches that are growing back toward the main trunk.  It is important with mayday to have a branch structure that is growing up-and-out from the trunk, and that each branch system has its space.  Inspect the crown for black knot disease, which appears as a small swelling of branch tissue in Spring, but later develops into a large, elongated black growth by late summer.  When removing black knot, cut back at least 6″ from the end of the “knot” to a lateral branch.  Do not leave a stub as this will look unsightly.

I find it useful to reduce over-extended lateral branches to prevent storm-damage from snow load.  Maydays and ‘Schubert’ chokecherries do not recover well if branches are bent severely by late-Spring or early-Fall snowstorms.

Crown Reduction and Shaping

Not recommended.  At planting, allow sufficient room in your yard for the mature form of this tree.  Mayday is not a very tall tree and the limbs are very strong so branch failure is unlikely. Shaping a mayday opens up the tree to further infection by black knot spores.  If a tree must be reduced in height, use proper reduction pruning cuts to limit the size and number of cuts made.

(c) 2015 Shane LePage, Wild Rose Garden & Tree Service Inc., Red Deer, AB.