Thuja root depth – how deep do trees of life take root?

The thuja (thuja) or trees of life are a genus of the cypress family, which in turn belongs to the order of the pine-like. Our best-known thuja, Thuja occidentalis, originally grew in the north-east of the USA and in eastern Canada, mainly around the Great Lakes. In a soil that is well supplied with moisture, thujas also grow on shallow water margins or in swamp areas. So always ready to absorb water just below the surface of the earth, and its roots have developed accordingly:

Thujas belong to the group of shallow roots, which in contrast to heart roots (heart-shaped roots with medium depth growth) and deep roots (carrot-shaped roots push themselves vertically into the depths) develop their roots directly below the surface of the earth. The thuja develops a dense, even network of roots, the individual root shoots of which spread out in the form of a plate in the upper soil layers and become finer and finer towards the outside.

The root depth is only one of the criteria that decides whether you will be happy with the new conifer in your garden or not. In terms of tree and building biology, thuja roots are assigned the following properties:

• Penetration of the roots in disposal lines is excluded
• The prerequisite is, of course, that the lines have been laid at the correct depth
• In this regard, some surprises may await on plots with historic buildings
• Thuja roots can be used to lift pavement or pavement that is laid horizontally
• If a thuja is close enough, it can even break up the pavement
• The distance to the topping should at least correspond to the expected diameter of the thuja
• If a tree of life is allowed to grow freely, the root can spread even further
• A disadvantage of the shallow root is moderate anchoring, so thuja should be protected from strong winds
• If the thuja is planted in a row like a hedge, the roots often fuse, which gives the planting more stability
• But even freely growing specimens can become very stable if they can take root in good soil

If you plant the thuja in such a way that there is enough distance to the next horizontally laid area and not face it straight in the main wind direction, there should be hardly any problems.

Choosing a location at Thujas: forever if possible

With the thuja and its roots, however, there are only no problems as long as the thuja is allowed to grow unimpaired. If there are any changes in the garden that require you to “get to the roots of the thujas”, it becomes critical.

Because a thuja root reacts negatively to all possible impairments:

• Thujas do not like mechanical interventions in the root space, as they occur during construction work or the like
• Covering with subsequently applied earth or other material is also not welcome
• In particular, the roots (the thickened transition from the trunk to the root) should not be covered
• Transplanting after one or two years of standing is almost impossible
• Because the thuja is supplied from the fine roots on the outside of the “root plate”
• These roots are severely damaged during transplanting even if the thuja is moved with huge balls

Therefore, the location should be chosen very carefully, especially with Thujas. Of course, in such a way that the thujas can grow well, i.e. in a place where the soil provides sufficient moisture. If thujas are planted in rather dry soil, they should be in the shade. In addition, you can keep the moisture in the soil a little longer with a thick layer of mulch on the outer root area and keep the thujas happy with additional watering in dry periods. You shouldn’t do thujas on hills from and in which rainwater runs off or through quickly.

Limit distances for trees of life

By the way, nobody will be able to tell you exactly what “growing flat” means in centimeters, downwards or to the side. Plants develop just as individually as animals and humans, and their immediate and wider environment, nutrition, water supply, etc. also have a major influence on their development.

You may be able to refer to the regional neighborhood law for information on the depth and extent of the root to be expected in your region – the more regional the standard, the more likely a biologist with a good knowledge of the local conditions was involved in the creation. The root depth is rather seldom regulated in local statutes – if you let roots grow in structures, that is your business first; only the spread of roots leads to neighborhood disputes so often that the legislature has created preventive rules.

In neighborhood law, minimum limit distances are regulated, and if they are observed, disturbance to the neighbors including damage to neighboring structures are rather unlikely, i.e. a good orientation. If you have the space, you should keep a slightly larger distance to other structures, paved areas and the neighboring property in order to prevent or minimize possible damage from the roots. Because the distances in the law are defined as cautiously as possible, so that reasonable planting is still possible even on the smallest home plot without a neighbor “disturbed by everything” being able to raise objections. A distance of 2.5 m is given as a general guideline, of course apart from any obligation.

Thuja: root spread and competition

The spread of the root is also of interest in the middle of the garden. If you want to plant thuja in a not very large plot of land, every inch of thuja root space counts because that is to some extent lost to the garden:

• Shallow-rooted woody plants absorb water and nutrients directly through the seeping surface water
• They like to swallow this surface water completely, so that there is hardly anything left for other plants in the catchment area (here, quite literally, increase)
• Other shallow-rooted plants usually cannot withstand this competition in the root area for long
• Plants with deeper roots often do not survive the rooting phase
• You don’t even need to try out ground cover that is densely rooted under thujas

In the vicinity of thujas, shade-tolerant plants will settle, which can cope well with the competition for roots from woody plants. These include B .:

• Aruncus (dwarf goat’s beard Aruncus aethusifolius)
• Asters (wild asters such as A. ageratoides, A. divaricatus)
• Bergenia hybrids
• Ground cover clematis (Clematis x jouinana ‘Praecox’)
• Convallaria majalis (lily of the valley)
• Heuchera (Purpurglöckchen)
• various Sedum species (Fetthenne, va Sedum hybridum ‘Immergrünchen’)

But you will have to water these plants separately / additionally and constantly pay attention to how much the thujas leach the soil. When the thuja are older and have deeply rooted the soil, a layer of compost soil has to be applied more often for the vegetation in the area (but see also “Covering”, especially the root approaches must not be touched).

Thuja occidentalis: It all depends on the right cultivar

Now you know the advantages and disadvantages of the shallow root. If it could get tight with your thujas in any direction (thuja must be planted very close to the paved path, etc.), you can still “tweak the fine control” by choosing the right variety.

Thuja occidentalis is easy to care for, easy to cut and super frost hardy (high-spirited researchers are said to have dipped thuja pre-tempered to frozen temperatures in liquid nitrogen of -196 ° C without noticing any negative effects); so popular all over the world where it can get really cold in winter. That is why there are around 120 different cultivars of this occidental tree of life with their own names. Not all of which are on the market in this country, but around a dozen Thuja occidentalis cultivars should be available in every reasonably well-stocked garden center.

“Officially”, that is, in textbooks and instructions, the roots of all thujas grow similarly. But an experienced gardener at a nursery near you will be able to tell you which non-rooted Thuja variety develops more compact roots in which soil (in your garden soil). But be careful: Allegedly weak dwarf thujas are not necessarily weak all around, but are usually grafted on normal thujas as bases. These “pairs” can be very active in the root area, which is why you should carry a variety on a weakly growing base if there is limited growth space.

The root space of other species of thuja

The other Thuja species are either less dangerous than Thuja occidentalis in terms of root depth or are only suitable for property sizes where the root depth is irrelevant:

• In total, the genus of thuja consists of 5 species
• Apart from Thuja occidentalis, only the giant tree of life Th. Plicata is planted more frequently
• But especially as a park tree, 50 to 70 m final height, not many private properties can handle
• The Korean tree of life Th. Koraiensis and the Japanese tree of life Th. Standishii are also rarely offered
• The first remains small, the second only grows a few meters high in Central Europe
• More root growth than with Th. Occidentalis is therefore not to be expected
• No. 5 is called the Sichuan tree of life Th. Sutchuenensis, an almost extinct Chinese exotic

Conclusion
Thuja are shallow roots that do not have a reputation for causing major damage to supply lines in the garden. But they like to lift flat surfaces nearby, their plant neighbors don’t have it easy either, and once ingrown thuja roots want to be left alone. No serious gardening expert will be able to specify exactly how much distance should be kept to slabs, strip foundations, etc.