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Its majestic stature, summer blooms and winter fruit decoration make pruning the trumpet tree seem tricky. In fact, all magnificent Catalpa species are well tolerated by pruning. Choosing the right date and professional pruning guarantee a successful course and do not require extensive gardening experience. Find out here when you should ideally prune a trumpet tree. These 4-step instructions get to the heart of the best way to proceed in a practical and factual manner.
Growth defines the ideal time
For the perfect pruning at the ideal time, it is advantageous if you briefly familiarize yourself with the special characteristics of a trumpet tree. Among the trumpet trees, it is primarily the trumpet tree that enjoys great popularity in the gardens of Europe. Native to the moderately dry floodplains in the sunny southeast of the United States, the deciduous tree has made a name for itself as an imposing shade provider with its broad, spreading crown. With rapid growth of 50 cm at a young age, a trumpet tree strives with vehemence to make it big in the garden, which is not always in the gardener's interest.
If enough space is available for a Catalpa bignonioides, it will grow to a height of 10 to 15 meters and develop a harmonious, broadly pyramidal crown that does not require a shape cut. The large, heart-shaped leaves are joined by white bell-shaped flowers with yellow-striped throats in June and July. In autumn, the exotic spectacle is crowned by pods up to 40 cm long, which remain hanging throughout the winter after the leaves have fallen. In order not to impair this display of splendor and still regulate the growth in size, the following two dates are available to you.
- Best date: In late winter during the months of January and February on a frost-free day
- Alternative: In August, immediately after the flowering period and before the establishment of new buds
The legislature also has a say in the choice of date. According to the Federal Nature Conservation Act, radical pruning of all types of trees and shrubs is prohibited between March 1st and September 30th. This statutory order serves to protect breeding birds. Only light grooming cuts are allowed during this time. Consequently, late summer timing is only an option if you are pruning this year's growth to reduce your Catalpa's dimensions. Since a trumpet tree is still wearing its dense dress of leaves at this time, the view for a more extensive shape and maintenance cut is blocked anyway.
4 step guide
If you have decided that late winter is the best time, even inexperienced gardeners can easily manage a professional pruning on the now leafless trumpet tree. The following guide explains how to do it right in just 4 steps.
The following preparatory work ensures that both the gardener and the trumpet tree survive the pruning safely. In the first step of these instructions, the focus is on the following safety precautions.
- provide a stable ladder
- Put on work gloves and safety goggles
- For branches up to 40 mm in diameter, have an anvil or bypass pruning shears ready to hand
- use a hand saw with a curved blade for thicker branches
- Disinfect all blades or saw blades with alcohol before starting work
For a trumpet tree up to a growth height of 5 meters, the specialist trade offers special Combisystem pruning shears. These special scissors allow you to have solid ground under your feet when pruning and still be able to make precise cuts at great heights without great effort. This is possible thanks to a branch attachment, a tear-resistant pull rope and a telescopic handle.
If you expect a large amount of clippings, a garden shredder will make disposal easier. Powerful devices shred even thick twigs so finely that the volume of waste is significantly reduced. At the same time, the clippings are transformed into a valuable organic fertilizer. Since investing in your own shredder is not always worthwhile, DIY stores and garden centers offer the devices for rent.
A trumpet tree is first thinned out so that you can correctly assess the extent to which the crown should be shortened. By removing the deadwood, all uncertainties about further cutting are eliminated.
How to do it professionally:
- cut off dead twigs on astring
- use the scissors just in front of the branch collar without damaging it
- Thin out the weaker ones from branches that cross or are too close together
- Remove branches pointing towards the inside of the crown
If you have any doubts about the actual condition of a shoot, subject it to a simple vitality test. With a sharp knife, scrape off a piece of the rind. If green or light-colored tissue appears underneath, the branch is alive and will not be removed. On a dead branch, the tissue under the bark is brown to dark brown.
If you tackle the third step of this guide, your trumpet tree will stand with an airy, manageable crown. After the obligation in the form of preparatory work and thinning out, the freestyle in the editing program now follows. The rule of thumb, especially for a Catalpa, is: as little as possible - as much as necessary. Fresh shoots and branches are often at risk of breaking on a young trumpet tree. Therefore, Catalpa should not be topiary every year, but at intervals of 3 to 5 years.
The following incision has proven itself in practice:
- Shorten branches that are too long by a third to a maximum of half
- apply the scissors 0.5 to 1 cm above a pair or triplets of buds
- Make the cut at a slight angle for better drainage of rainwater
To maintain the beautiful, natural crown shape, please do not cut off a branch anywhere. Choose the cutting point so that there is a branching side shoot immediately below. This cutting technique is called 'deriving' in technical jargon and ensures that no unsightly, broom-like shoots develop as the growth progresses. You only shorten the main shoot if you want to motivate the crown to grow particularly bushy. Any cut on the main drive affects stability and increases the risk of breakage.
Very strong branches with a diameter of 30 mm and more require the use of a saw. In this case, proceed in 3 stages. First saw the branch in half from below about 40 cm away from the trunk. Then set the saw 45 to 50 cm away from the trunk and saw from above until the branch breaks off. In this way you prevent a frayed cut. You can now easily saw off the remaining stub on Astring.
Current research results in tree surgery radically clear up the traditional use of wound closure agents after a tree pruning. As has been shown in decades of experiments, such preparations impair the self-healing powers of woody plants. Rather than preventing disease and rot, it actually encourages these problems. Injured wood tissue cannot heal like human skin. Rather, cuts are overgrown by a layer of callus to seal them off from the rest of the tree. Spread over this layer of callus is a layer of fresh, active cambium wood. If the pruning measures on the trumpet tree take place in late summer, you can do without wound closure agents.
Wound treatment only makes sense for cuts after a winter cut. Since the fresh cambium cannot grow outside of the vegetation period, it should be protected from frost and moisture until spring. To do this, smooth the edges of the wound with a sharp knife. Then apply a thin layer of tree wax along these edges. The inside of the cut is not treated.
Special case: ball trumpet tree Catalpa bignonioides 'Nana'
Is your trumpet tree the 'Nana' top graft with a spherical crown and constant height? Then you have various pruning options. Since the small tree does not bloom and bear fruit, a radical pruning cannot remove buds that have already formed. Furthermore, the hybrid no longer gains height. The growth is limited to the volume of the crown, which you can easily regulate with a cut in winter.
Please choose an overcast day before March 1st with temperatures around + 2 degrees Celsius. Trim all shoots to desired length as outlined in this 4-step guide. As long as at least one pair of leaf nodes remains on a branch, it will sprout again in spring from these sleeping eyes. A radical cut has also proven itself to repair storm damage on the orb trumpet tree. On the other hand, if you are aiming for a larger crown, only cut back branches that are growing out of shape every 4 to 5 years.