The Oak, the Included Bark, and the Client with a Deadline
A 30 cm DBH, 14 m tall northern red oak stands in a front yard. At 4 m there is a codominant union with included bark; the smaller stem is 20 cm across at the union and leans over the driveway. On the opposite side, the lowest limb extends over the driveway at 3.6 m. The client wants the crown thinned by 30%, everything below 6 m removed, and the top cut back so the tree stops getting taller. It is late May, and oak wilt is known to occur in the county; the nearest confirmed case was 6 km away. The client is a reliable payer, has read that oaks should be pruned in winter, and wants the work done this week because a family event is coming.
1. Sort the requested work into what you will do, what you will defer, and what you will refuse, and explain why the timing matters.
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Will do: structural work on the codominant union, minor deadwood removal, and a small amount of clearance pruning on the low limb.
Will defer: the 30% thin and the raise to 6 m - not because they are technically prohibited, but because they are the wrong work, discussed below.
Will refuse: topping.
Timing. Late May in a county with oak wilt is the worst window to wound an oak. The fungus is spread by sap-feeding beetles attracted to fresh wounds, and spring and early summer wounds are the highest risk. Standard practice is to prune oaks in dormancy - after leaf drop, before bud break - and to avoid the spring period entirely where the disease is present. A family event is not a hazard, so there is no justification for wounding the tree now; the work can wait six months at no cost to anyone. If a genuinely hazardous limb had to come off this week, the correct approach is the minimum number and size of wounds, made cleanly, with a thin coat of wound dressing applied immediately - one of the few situations where dressing is supported.
Correct one misconception for the client. Pruning in late spring does not bleed an oak to death and sap loss is not the concern. The concern is infection, and it is specific to oaks and specific to the season. Say it that way and the client will wait.
2. Explain what you will do with the codominant union and why not remove the smaller stem now.
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The defect is real. Included bark means bark is trapped in the crotch, so there is no continuous wood fibre joining the two stems - just a wedge. That union gets weaker as both stems thicken, and the smaller stem leans over a driveway, which is a target. Doing nothing is not an option.
Why not cut it now. The smaller stem is 20 cm against a 30 cm trunk: two thirds of the trunk diameter at the union. Cutting it in one operation leaves a wound of that size, which the tree will never close, on the side of the trunk carrying a large share of the crown. The sudden loss of leaf area and the shift in load happen at the same time.
What to do instead: subordinate it over several cycles. Make reduction cuts on the smaller stem, each one back to a lateral that is at least one third the diameter of the part being removed, taking roughly 30-40% of that stem's length and weight per visit. Keep the lower, inside laterals - they keep the stem supplied while it shrinks. Over three or more cycles the smaller stem's share of the crown gets small and one clear dominant leader emerges; then remove it with the smallest wound you can arrange. This is slower, more skilled and more expensive per visit, which is exactly why it needs to be sold properly rather than skipped.
Inspect each visit for a crack at the union, a raised ridge, or movement - those change the plan from pruning to a risk decision. If the union is already cracked, cabling or bracing may be appropriate as a supplement to structural pruning, never as a substitute, and removal of the tree becomes a legitimate option to put to the client.
3. Write what you would tell the client about thinning, raising to 6 m, and topping.
Read the worked answer
Thinning by 30%. Thinning is not a height reduction, and it does not make a tree safer. Removing 30% of live foliage exceeds the usual guideline maximum of about 25% in a single pruning, and heavy thinning - lion-tailing - leaves the remaining branches to take the full wind load and can make failure more likely, not less. It also triggers a flush of epicormic sprouts along the limbs, which is uglier than what you started with. If the real concern is a specific weak limb, we address that limb.
Raising everything to 6 m. On a 14 m tree, clearing all live limbs to 6 m removes a large proportion of the crown and leaves a row of large wounds at one height on the trunk. The usual clearance over a residential driveway is around 4.2-4.5 m, and the limb at 3.6 m only needs to come up slightly to meet it. Raising the rest buys nothing and costs the tree a lot.
Topping. I will not top it, and here is why in plain terms: topping makes large wounds that decay, and the regrowth comes back as a dense broom of shoots attached to the outside of a decaying stub - heavier, weaker and more dangerous than what was removed. The tree will also not be shorter in ten years. If height is genuinely the issue, crown reduction by cutting back to laterals at the outer edge, spread across several cycles, is the legitimate alternative - but a 14 m oak is not an unusually tall yard tree, and the more useful conversation is whether this tree belongs in this yard at all.
Deliver it as a written, signed plan: a three-visit structural pruning programme starting in dormancy, the clearance work this winter, no topping, and a review of the union each visit. The client keeps the tree, you keep the relationship, and the tree gets the work it actually needs.