Cork oak branch development

Healthy oaks can grow quickly in spring. When the spring flush hardens off, it’s a good time to prune.

Cork oak – container by Sara Rayner

I last worked on the tree in August. Because it’s grown so much since then, I expected the wire to start cutting in.

Wire starting to cut in

Wire marks

I find that this is a good amount for the wire to cut in. If I’d removed the wire earlier, the branches would have lost more of their shape. If I’d left it in place longer, the scars would be more obvious.

I started work by removing all of the wire. Next, I cut back the upper branches with the goal of keeping up to 1/2″ inch of new growth as I want to keep the internodes short. Here’s the tree after pruning.

After pruning

Branch detail

I left the lower branches long as I want them to thicken before I reduce them. Cork oaks have strong apical dominance and I’ve found that the lower branches don’t thicken when the upper branches grow freely.

I also wired a few of the branches, but found that most already had good movement and only needed to be lowered. For these branches I applied guy wires. Altogether I used seven of them.

Guy wires secured to a wire inserted in a drainage hole

Here’s the tree after pruning and wiring.

Cork oak – 16″

Right side

Once the new buds come out, I’ll remove those I don’t need and let the others grow until fall. (See “Cork oak pruning follow-up” for details.) If the top branches get too strong, I’ll reduce or remove them along the way. I plan to prune the tree again in either fall, winter, or early spring – anytime up until it starts growing again in spring.