Black Lumps on Your Cherry Tree in Richmond Hill?

You notice it once the leaves drop: odd black growths along the branches of your cherry or plum, hard and crusty, a few centimetres long. They look like something stuck to the twigs. They are part of the tree, and the cause is a fungus called black knot.

What Black Knot Is

Black knot is a fungal disease of trees in the Prunus family. In Richmond Hill yards that means sweet and sour cherries, plums, flowering cherries and, most of all, the purple-leaved Schubert chokecherry that builders planted along so many streets and front lawns in Jefferson, Westbrook and Rouge Woods.

The fungus gets into young twigs in spring, when rain splashes spores from old knots onto new growth. Nothing shows for months. The next spring a soft, olive-green swelling appears. By the following winter it has hardened into the black, tarry lump you see now, and that lump starts releasing spores of its own.

Why It Matters

A single knot on a thin twig is a small thing. The trouble is that each knot girdles the branch it sits on. The swelling cuts off water and sugar moving past it, so everything beyond the knot dies over a season or two. Left alone, a tree collects more knots every year, loses more branches, and starts to look thin and ragged.

Knots on the trunk or on the main limbs are the real concern. You can cut a twig off. You can’t cut out the trunk, and a trunk ringed with black knot will eventually fail or decline to the point where the tree isn’t worth keeping.

How Bad Is Yours?

Walk around the tree and count. A rough count tells you which of three situations you are in.

A Few Knots on Small Branches

This is the common case and very manageable. Cut those branches out in late winter and the tree can carry on for years.

Dozens of Knots Through the Crown

The tree is losing ground. Heavy pruning can still help, but you will lose a good share of the canopy and you will need to check it every winter.

Knots on the Trunk or Main Stems

This is where we usually talk honestly about whether the tree has a future. Often the kinder choice is to take it down and plant something that black knot leaves alone.

The Right Way to Cut It Out

Timing and technique make the difference between clearing the disease and spreading it around the yard.

• Wait for late winter. February and March are ideal. The tree is dormant, the knots are easy to spot on bare wood, and the fungus isn’t releasing spores yet.
• Cut well below the swelling. The fungus runs inside the branch beyond what you can see, so the cut goes 15 to 20 centimetres below the knot, back to a healthy side branch or the branch collar.
• Clean the tools between cuts. Wipe blades with rubbing alcohol so you don’t carry the fungus to the next branch.
• Get the knots off the property. A pruned knot lying on the lawn can still release spores in spring. Bag the cuttings and put them out with the garbage rather than the yard waste.

On a small ornamental cherry a careful homeowner can handle the low twigs from the ground. Anything higher, anything near the trunk or anything that needs a ladder is where Scott and the crew come in. We take out the infected wood, shape what is left so the tree stays balanced, and haul every cutting away. Our trimming and pruning work covers this kind of careful, selective cutting.

Will It Come Back?

Possibly. Spores drift in from wild chokecherries along the ravines and from other trees on the street, so even a cleaned-up tree can pick up new infections. The difference is that a tree checked every winter never builds up a heavy load again. Five minutes looking at bare branches each February is the best protection you have.

If your neighbour has a badly infected cherry right beside yours, it is worth a friendly word. Their knots are seeding your tree every spring.

Richmond Hill Notes

Pruning out diseased branches is normal tree care. Taking a tree down is different. Under the City’s Tree Preservation By-law 19-25, private trees with a trunk 15 centimetres or wider at chest height need a permit before removal, so a mature cherry often qualifies. If the tree turns out to be past saving, we’ll talk through the permit question when we come out, and the City has the final word.

Many Schubert chokecherries in newer subdivisions stand on the City boulevard, not your lot. If yours is between the sidewalk and the road, don’t prune it. Report it to Access Richmond Hill and the City will look after it.

Planning the Winter Cut

Knots out of reach, knots on the trunk, or simply wanting a frank opinion on whether the tree is worth the effort: any of those is a good reason to text a picture of the worst branches to (289) 475-5822. Scott can usually come by the same day to give you a free quote and put the job on the late-winter list, when the cuts do the most good. We pick up the phone daily, 8am to 8pm.