When to Prune a Globe Catalpa (Nana) and How to Do It Step by Step

Step by step

1. 1

   Pick the right time

   The best moment for the hard pruning of a globe catalpa is late March to early April, just before the buds open. Choose a frost-free, dry day. Pruning in early spring gives the plant the whole season to rebuild a compact crown.

2. 2

   Prepare clean, sharp tools

   Cut thin shoots with pruners and thicker ones with a garden saw. Disinfect the blades, for example with rubbing alcohol, so you do not spread disease. A blunt tool crushes the shoot and the wound heals far worse.

3. 3

   Shorten last year's shoots to 2-3 buds

   Cut each shoot from the previous year back to just above the second or third bud, counting from the base of the shoot. Cut about 0.5 cm above the bud, at a slight angle. Over time, knobs form at the cutting points, and new shoots sprout from them every year.

4. 4

   Remove diseased and inward-growing shoots

   Cut out twigs that are broken, dry or frost-damaged, along with any that cross or point into the center of the crown. This keeps the crown better ventilated. Cut at the branch collar, without leaving long stubs.

5. 5

   Cut off suckers from the trunk and below the graft

   A globe catalpa is grafted onto a trunk, so shoots sprouting from the trunk or below the graft point are rootstock suckers - they grow differently from the crown. Remove them as they appear, cutting close to the trunk. Left in place, they will ruin the globe shape.

6. 6

   Prune the natural form only for health

   A catalpa growing freely in its species form is kept as a large tree with flowers. Limit pruning to removing dry, diseased and crossing shoots. Save the hard annual pruning strictly for the globe form.

7. 7

   Care for the tree after pruning

   You can smooth larger wounds with a sharp knife so they close faster; sealing is usually unnecessary. Water the plant during dry spells after pruning. A spring feed of compost will support the rebuilding of the crown.

Why a globe catalpa needs pruning every year

The Nana variety does not flower - all its beauty lies in the dense, globe-shaped crown of large, heart-shaped leaves. Without pruning, the shoots quickly stretch, the crown turns loose, sprawling and thin, and branches can snap under the weight of the leaves.

A hard annual cut back to 2-3 buds forces the plant to push out many short, strong shoots close to the crown. The result is a tight ball that holds its shape all season. It is the same mechanism as pollarding - with each year, distinctive knobs build up at the cutting points.

What happens if you prune too late or not at all

Pruning after the leaves unfold weakens the plant, because the catalpa has already spent its reserves producing leaves that you then remove. The tree regrows weakly, looks thin all season, and loses more sap from thicker cuts. If you must correct the shape in summer, keep it to a gentle touch-up.

Skipping the pruning year after year gives you an ever larger, sparse crown on a thin trunk. Such a head falls apart easily, breaks under snow and loses its regular shape. Getting back to a tight ball then takes a hard renovation cut in early spring.

Pruning a young catalpa

In the first years after planting a grafted globe catalpa, let the crown fill out a little so it forms a solid framework of a few main shoots. Shorten the new growth even then, but less radically than on an older tree. Once the crown reaches the size you want, switch to the hard annual cut back to 2-3 buds.

Keep an eye on the trunk the whole time and remove any shoot or sucker below the crown immediately. It is also worth tying a young tree firmly to a stake, because a large, heavy head on a thin trunk is vulnerable to wind.

Frequently asked questions