What are deep rooters? – Trees and shrubs for slope stabilization

The root system consists of all the roots of a plant, the terms root network or root system are also used as synonyms. There are different types of root systems, in several ways:

1. A distinction is made in relation to the root components

• Homogeneous root systems, made up of numerous, similarly growing roots with the same tasks
• Homogeneous root systems form vascular spore plants (ferns and clubmoss plants) and monocot plants, e.g. B. Sweet grasses (all cereals) and orchids
• Heterogeneous root systems, two types of roots, a main root growing vertically into the ground, from which lateral roots branch off
• Heterogeneous root systems are formed by dicotyledonous plants, i.e. all seed plants except for the above-mentioned ferns and Co.

2. With regard to the shape of the root system (the so-called root pattern), a distinction is made between three basic types of woody plants:

• In the taproot system, a strong, vertically growing main root dominates
• Most deep-rooters form a deep-reaching taproot, e.g. B. oaks, pines, firs, elms (each with exceptions)
• A central root system sends several roots of different strengths side by side into the soil, e.g. B. birch, beech, hornbeam, larch, linden (again with exceptions)
• In the case of the horizontal root system, the young tree forms a main root, which then divides into several horizontally growing lateral roots, e.g. B. many poplars
• The sinker root system is a mixed form in which so-called sinker roots develop from initially horizontally growing, strong roots, which grow vertically into the ground (ash tree, spruce in the mature phase)

3. A distinction is made with regard to the direction of growth

• Shallow-rooted plants that send their roots horizontally just below the surface, e.g. B. to absorb seeping surface water or because there is no other way because of rock just below the surface of the earth
• Deep-rooting plants that drive their roots deep into the ground, e.g. B. to advance to the groundwater

4. With regard to the growth structure of the root sections, a distinction is made between – often woody – coarse roots and fine roots:

• Coarse roots grow into the root structure, which gives the plant support and structures and delimits the rooted soil area
• In between, the fine roots “let off steam”, thin and often only short-lived, but all the more important: They manage the absorption of water and nutrients – the reason for the constant warning to be read that one should please be careful (when repotting, transplanting). bypass the roots.

Which roots grow deep?

How deep a root grows and how wide its root radius will grow depends on many factors. The shape of the roots cannot be precisely predicted, neither for the tree species nor for the individual plant, various factors influence:

• The vitality of the wood plays a role
• How many times the tree was transplanted in its youth, which stimulates root formation
• In compacted soils, with waterlogging, with high groundwater levels, downward root growth is low
• However, the tree can spread far beyond the crown area in the ground
• It is also influenced by whether the tree stands alone or is disturbed in root development by competing roots
• This then decides at the same time on a windy-exposed location or protection by surrounding trees, with corresponding root formation

How deep a root grows cannot be read from the size of the tree either, there is no fixed ratio: a 50 m high sequoia stretches its roots exactly the same 2.3 m deep into the ground as the 2 m high yew; the 12 – 18 m high Scots pine creates a stately 10 m root depth in very dry locations.

In search of the deep rooter

If there is a reason why you are so keen on planting a deep-rooting plant, for soil stabilization or lack of room for extensive root zones, be warned not to take blanket statements.

The gray theory just described leads to certain genera of trees and shrubs being flat-rooted or deep-rooted, because most species of these genera have the potential for shallow-rooting or deep-rooting and usually grow in environments in which they really are shallow-rooting or deep-rooting .Become deep rooters.

Such generalizations are particularly common when a certain species or cultivar is planted quite often in the garden. The gorse, Cytisus, is z. B. a deep root, of which the cultivar Cytisus x praecox, broom or noble broom, is very well known. Cytisus x praecox is a flat-rooter, so all brooms that can be planted over the basement ledge etc. are quickly considered to be flat-rooters – which goes terribly wrong if a broom is chosen.

Because if a particular root system is found in a genus, it is far from imperative that the other species in that genus develop the same root system – trees are imaginative when it comes to nutrients (food), just like some domestic animals.

The first two distinctions between root systems that have just been outlined can give initial indications: sweet grasses and ferns hold the ball, or here the roots are certainly rather shallow, horizontal roots also only make their way a little deep, sinker root systems are also initially in the horizontal employed. Plants with a central root system and a taproot system remain as potential deep-rooters, and these are the ones where the most deep-rooters can actually be found.

But the whole thing can be thoroughly deceptive, horizontal roots go quite deep if they e.g. B. belong to a primeval redwood (Metasequoia glyptostroboides). Sinker root systems are so called because sinker roots grow vertically downwards from the “completely grown” horizontal roots. Monocots with (apparently rather reticent) homogeneous root systems also include palms, which can develop an impressive underground stilt root system.

There are also trees that replaced “juvenile, strong taproots” with increasing age with deep and far-reaching sinker roots (such as the stone pine or Swiss stone pine); Here are a few types of deep rooters:

• There are deep-rooted taproots in fir, pine, ash, juniper, yew, bald cypress and oak
• Chestnuts, honey locusts, sweetgum trees, primeval redwood and Chinese redwood are deep-rooted plants without a taproot

But as I said, it depends on the individual case, and a number of well-known trees are deep-rooted and shallow-rooted at the same time, for example beech, Scots pine, acacia, hemlock and golden elm.

So if you want to buy a deep-rooted plant with a very specific root shape, which will not surprisingly change this shape for you later, you should first make a rough selection based on the basic root system – and then look very carefully for the individual species, what ideas this tree has developed during root growth.

The “gardening tasks” of a deep rooter

Colloquially, the typical deep rooter is the opposite of the flat rooter, a plant with a deep and straight root reaching into the ground, a taprooter.

These taproots have their tasks in the garden:

• There are taprooted vegetables that provide deep soil loosening and bountiful harvests
• These are, for example, carrots and radishes
• Other taproots such as B. the mullein combine soil loosening with food supply for rare small creatures such as the leafcutter bee
• Other taproots serve as soil conditioners by producing nodule bacteria, such as broom
• They can also be used as fast-growing soil stabilizers on soil that is too loose
• In organic farming, taproots come after flat and medium roots in mixed cultivation
• The taproot is a good house tree; its roots, which grow vertically downwards, do not damage the house foundation
• And it is usually more suitable for standing on the terrace or pond because it does not damage the floor covering or the pond liner

The typical deep-rooting plant can therefore possibly help with slope stabilization, but actually it depends on completely different criteria:

Trees and shrubs for slope stabilization

The taproot just discussed is not the star of slope stabilization. The plants used to stabilize the slope should have deep and broad roots in order to secure the slope in every direction. There is a whole range of woody plants that have already proven themselves many times over in this regard:

• Cytisus scoparius, broom, height up to 2 m, deep roots, nitrogen-fixing bacteria in the root nodules
• Juniperus communis, common juniper, up to 12 meters high, deep root system
• Lonicera pileata, hedge myrtle, evergreen, vigorous, spreading plant, up to 1 meter high, extensive shallow roots
• Potentilla fruticosa, cinquefoil, grows up to 1.3 m high, densely rooted, shallow roots
• Rosa canina, dog rose, reaches a height of about 3 m, deep-rooting
• Rosa rugosa, apple rose, potato rose, up to 1.5 m high, flat roots forming runners on the sides, and many more trees and shrubs that, in addition to pronounced deep, can also develop rather shallow root systems, heart root systems or sinker root systems.

The use of a taproot as part of a slope reinforcement is conceivable above all as a structural plant on a fairly extensive slope: Shrubs with taproots distributed at regular intervals ensure vertical deep stabilization, plants with roots are planted in between, which spread out and cover the ground on different “storeys”. root through. The upper end is formed by ground-covering perennials that form runners on their shoots or roots, the last part of the dense network that protects the soil from erosion.

For this, it is particularly important that the roots of these plants grow nice and dense and penetrate the soil evenly. The slope reinforcement works in layers, so to speak, deep-rooted plants with well-developed root systems secure the soil in depth, plants with roots that do not grow quite so deep continue this work above it, and the end is formed by plants rooted more broadly and in the top layers of soil.

Which of these root depths are used at all depends on the thickness of the soil layer on the slope, for a little soil on a dry stone wall z. B. only the surface roots needed. For use in the top layer, e.g. B. the following plants:

• Alchemilla, lady’s mantle
• Epimedium, Elf Flower
• Geranium, stork beak
• Hedera, Efeu
• Hypericum calycinum, St. John’s wort and other self-propagating species
• Lamium, gold nettle, with different dispersal mechanisms, e.g. B. Fertile and sterile stolons
• Pachysandra, Ysander
• Waldsteinia, Waldsteinie, all species form rhizomes in the soil

The compilation of a plant community that grows harmoniously with and within one another for slope stabilization requires a little consideration for known cooperation and competition between the various species. If a slope is rather uncritical to fix because of the low incline, you can select your desired plants, maybe read up briefly whether there are any known intolerances and otherwise just try out which plants get along well.

If the slope almost needs structural reinforcement due to its degree of steepness, the plant community should be carefully mixed, if in doubt with the involvement of a specialist. It can also be useful to walk through the neighborhood, perhaps you have already gained experience as to which plants thrive particularly well (together) at the location.

Ideally, the whole thing then results in a kind of lattice structure of roots in the ground, which hold the ground where it should be even on fairly steep slopes – perhaps initially supported by fabric mats or plant nets.

Conclusion
There are different types of deep-rooters that can be used for different tasks in the garden. Not only deep-rooted plants are suitable for fixing the soil on a slope, but also plant communities with different root systems, the plants that develop particularly dense and lush roots. The optimal plant community on the slope roots through it “in tiers” until not a crumb stirs from its place.