When you’re planning an outdoor landscape for your home, there’s definitely a lot to think about.
Everything from layout and watering needs, to how plants and trees change through the seasons.
You also need to be cautious of a tree’s root structure, as lots of tree species can grow fast and their roots may cause damage which will be expensive to repair.
The 5 best small trees with non invasive roots include the Adams Crabapple Tree, the English Holly Tree, the Amur Maple Tree, the American Hornbeam Tree, and the Dwarf Plum Tree.
They all have root systems that either grow in shallow soils, or do not strangle or destroy surrounding plant species or hardscaping features.
Do Your Research Before Planting Any Tree
Before you even consider small trees as part of your landscaping you should know how big the tree will grow and how far the roots will reach.
Know the level of each plant species and consult with a nursery or landscape gardener prior to planting any tree so you don’t go damaging the roots and potentially harming other plants, paving, underground piping, or building structures that may be nearby.
Trees that sprout large lateral root systems are not always suitable to congested urban areas as their roots can meander and strangle other plant species.
Did you know? Having plants with heavy, wandering root systems too close to man-made infrastructure, is also a problem.
Root Systems of Trees
Tree root systems can be categorized into three varieties:
- tap root systems
- lateral root systems
- heart root systems (also known as oblique root systems)
Tap Root System
A tap root system has one primary root that goes straight down from the spree trunk and acquires a water supply that supplies nutrients for the tree to grow above ground.
Lateral roots are the smaller roots that develop from the primary root. A tap root system is very stable and has highest relative stability of the three types of root systems and do to stability is very common in many tree species such as:
- Walnut
- Oaks
- Pines
- Hickory
- Sweetgum
- Tupelo
Lateral Root System
As the name implies a lateral root system spreads out laterally and is providing and very solid base structure above ground to the tree.
Lateral root systems are not limited for the most part to one type of tree / shrub, they are found in 80 % of tree species. Some of these trees with lateral root systems may not perform well in a city due to the widespread nature of the root system.
Common trees found with lateral root systems include
- Ash
- Birch
- Cottonwood
- Hackberry
- Maple Trees
Heart Root System
The heart root system (also called the oblique root system) supplies stability to the tree by supplying the root ball to the tree which is a saturated mass of soil IF planted deeply.
With this weight the root ball provides anchor for tree above ground while allowing for creation of a counterweight.
This system may be very stable on dry ground, but at high risk of failure on wet ground or in flood-prone areas.
Heart root trees are mostly found in arid climates like the Mediterranean.
A few examples of tree species with heart root systems found in the US are:
- Honey Locust Trees
- Red Oak Trees
- Sycamore Trees
Top 5 Small Trees with Non-invasive Roots
Here is our top 5 list featuring the best small trees for your backyard or landscaping project.
1. Adams Crabapple (Malus ‘Adams’)
Adams Crabapple grows to height or even-width to 20-25 feet. It is a broad-round deciduous tree, produces small edible fruits, and superb display of pink flowers each spring.
Crabapple Root System
Crabapple trees are classified as small tree species with a non-invasive and semi-aggressive root system.
Crabapple roots are generally surface roots and have a lateral root structure; however, they do have sections that penetrate the (soil) for water collection.
Keep in Mind: Crabapple tree root systems do not typically damage hardscape features, but make sure to space your crabapple trees for growth and non-crowded trees.
Spacing Your Crabapple Trees
While you still need to consider the spacing of your Crabapple trees, try not to plant them too close to hardscape features such as pathways, driveways, septic systems, or any underground pipes or systems.
2. Dwarf Plum Tree (Prunus domestica)
Also known as the “Johnson” plum, this tiny tree is maybe the most humble on the list because it will typically grow to be about 8-10 feet tall when fully mature.
A native to Japan, but has naturalized across parts of Europe and North America, it grows best in USDA zones 5-9.
Throughout the Spring and Summer, this tree produces edible fruit that has dark red skin and red or pink fleshed interior.
This is a hardy plant, and prefers moist, clay or loamy soils.
Dwarf Plum Root System
Like the majority of fruit trees, the dwarf plum tree has a lateral root system where the roots grow out in all directions through shallow soils.
The roots of a fully mature tree will typically spread about 8-10 feet out in every direction, and will not be considered invasive to other plants or structures.
Spacing Your Dwarf Plum Trees
Dwarf plum trees thrive in bright direct light, and do poorly when overcrowded by other plants or trees.
If you plant them in your backyard, make sure to put them in the south section, and they will need to be on the south side of your house to receive about at least 6 hours of sunlight each day.
Action to Take: A single plant will require a fair bit of space of about 10-12 feet at a minimum. If you are planting in rows, space at least 10-14 feet from each other on all sides.
3. American Hornbeam (Carpinus caroliniana)
The American hornbeam (commonly known as the Musclewood or Ironwood) is a deciduous hardwood tree that can reach a height of 30 ft.
And it grows naturally in Eastern North America, and is a common species for urban landscaping settings where American hornbeams can have moist soils, in a naturalized area, or planted along streams or ponds.
American Hornbeam Root System
American hornbeams develop a lateral root system that typically extends deep into the ground.
Below the surface, American hornbeam roots are shallow, spreading laterally and oftentimes widely.
American hornbeam root systems do not produce major surface-related problems, and they are not considered harmful to other plant species or to hardscape elements.
Spacing Your American Hornbeam Trees In Your Backyard
Although the root system is not particularly invasive to plants or buildings, they disperse widely.
Be careful not to overcrowd your American hornbeam trees, and leave ample space for them to grow.
They are a stout tree and often have two forks or more off of the trunk, so leave at least 10 feet between any building and/or hardscape features, including driveway and sidewalk.
4. English Holly (Ilex aquifolium)
The English holly (a.k.a. the Christmas or European holly) has a growth habit that can be a flowering broadleaf tree that can reach an incredible 40 feet, although in urban settings it tends to be a small tree at around 10-15 feet.
The leaves of holly trees are stiff, dense, dark green, glossy, spiny along the edges, and play a lifesaving role when the foliage is fallen.
Even better: The female holly produces fragrant flowering in the summer, which by the fall, is transition into dark red, edible berries.
English Holly Root System
The English holly tree that uses a tap root system, and there it has very deep and strong roots that generally grow between 17 – 25 inches below the surface.
The primary tap root will grow straight downward from the shrub or tree main trunk and the root system isn’t considered overly invasive to other plant species.
However, the English holly root system can be destructive if planted above utilities, pipes, sewerage, etc. because the roots penetrate downward and creates significant issues when they’ve reached it.
Where to Plant Your English Holly Trees
English holly can be tamed to shrub / hedge, or it can be grown into a small tree. Whatever landscaping design you go with, when it comes to English holly, you’ll want to build some room for it to grow.
Don’t plant English holly too close to pavements, sidewalks, or driveways since the berries can fall and stain.
If you want to grow holly into a small tree, then allow 8-10 feet between every tree.
The English holly roots won’t invade, so they won’t negatively impact other nearby plants.
5. Amur Maple (Acer ginnala)
The Amur maple is a deciduous shrub or small tree that grows to a height of about 20 feet. It grows in Northeast Asia. We say “shrub” but it’s still a small tree.
In the fall, the leaves display a vibrant red that fades in to orange, and then yellow.
Amur Maple Root System
Like all maples, the Amur maple has a heart root system, which consist of thin, shallow branching roots which are fibrous, and non-invasive to surrounding plant-types and hardscape elements.
Warning: Amur maple trees prefer moist, well-drained soil, but because they are a heart-shaped rooting tree, they are prone to falling over in wet or saturated soils.
Spacing Requirements for Amur Maple Trees
Always create 10 feet of distance from each shrub to any hardscape feature.
Create 10 feet of space between each shrub to accommodate the shrub growth, and to avoid damaging any hardscape features.
In the fall Amur maples lose all of their foliage, so it is best not to plant close to driveway or paved surfacing, since the foliage will fall, and could stain.
Do not plant an Amur maple on top of your septic tanks or other underground utility components since the root structure may cause damage as the tree reach its full height.
Summary
In general, it is always best to use tree species that are minimally invasive in terms of their root structures for any backyard or landscaping projects.
Always research any trees that you want to incorporate, and see what the final size is expected to be, and what the spacing requirements are.
Do not plant any trees close to any existing structures and make sure to account for any underground utilities such as sewer, septic, or water piping, which depending if damaged could cost a lot to repair.