Relocating a tree won't be possible without heavy machinery, at least if the tree is a bit older. Photo: dpa
Transplanting a tree is always risky. While young trees handle the stress quite well, it can be a death sentence for large, established ones. Thorough preparation is therefore essential.
“Every tree adapts to conditions at its long-standing location. It knows exactly which way the wind blows, where it can find water and where nearby trees are – it exchanges information with its surroundings,” says Christian Honig, a tree protection expert at the environment and nature conservation organization Friends of the Earth Germany (Bund).
The older a tree is, the better it has acclimatised to its environment. And the harder it is to uproot and replant successfully, be it in the same garden or somewhere else.
“It’s difficult and very complicated for trees over 15 years old, but entirely possible,” says Christopf Dirksen, chairman of the North Rhine-Westphalia Tree Nursery Association in Mecklenheim, Germany.
Simply digging out a tree and replanting it somewhere else will almost surely fail. So you should plan on a lead time of more than just a few months.
“Large trees need two to three years of preparation,” says Michael Henze, a manager at the Federal Association of Horticulture, Landscaping and Sport Grounds Construction (BGL) in Bad Honnef, Germany.
The preparation begins by pruning the tree’s roots and canopy. For older trees, it’s advisable to do this over several growing seasons. For younger ones, pruning during the growing season preceding the transplantation is sufficient.
To get the root ball into good condition for taking root at its new location, dig a trench around it, slicing off superfluous roots with the spade. The outer edge of the trench will later be the periphery of the root ball, explains Henze.
The trench should be deeper than the tree’s main root area and have a width of at least 20cm. It shouldn’t be too narrow, as you want to preserve as much root mass as possible. Henze recommends that the diameter of the root ball be at least 12 times greater than that of the tree trunk.
The tree should not be planted any deeper than the depth it was used to from its previous location. This way you can avoid a lack of oxygen, which would suffocate the tree.
When you dig the trench, you’ll unavoidably clip long, fine feeder roots that extend far into the soil and supply the tree with water and nutrients. So it’s important to subsequently fill it in with a special substrate containing substances that promote root growth. And you’ve got to regularly water the root ball well.
If all goes well, the tree will grow new feeder roots on its root ball, which it vitally needs to get established at its new location.
“You should leave as much soil on the root ball as possible so that many small roots can form,” Henze says.
If a crane is used, you need to take care that the tree's bark bark isn't squeezed too hard. Otherwise it may die.
At the same time, you should prune the tree’s canopy by as much as 50%, preferably when the tree is in its dormant state and without leaves.
Transplantation of the tree must also take place outside the growing season, and definitely not when it’s still carrying leaves or fruit. The right time in the temperate zone of the Northern Hemisphere is from November to the end of April at the latest. It’s important that temperatures be above freezing.
“A large tree is extremely heavy and often can’t be moved without heavy equipment,” notes Honig. A crane or machine tree spade can do it. The tree’s new location should be as similar to the old one as possible as regards soil conditions, prevailing wind direction and sun exposure. – dpa/Katja Fischer
