Fig tree roots generally are very invasive, although much depends on the tree’s variety, its planting location, and the overall soil quality. Most fig trees, if they are planted in optimal conditions, spread their roots far and wide, which can make then troubling if they are planted in the center of a landscape design. These trees usually do best on the outskirts of a yard or surrounded by plenty of open space. Gardeners can often take steps to minimize root invasion by planting trees in pots or building underground retaining walls to keep the roots structured.
Much of a fig tree’s invasiveness depends on its variety. All fig trees are members of the ficus family, which is marked by shallow, fast-spreading roots. Still, smaller trees such as the celeste or Malta fig trees typically keep their root systems more or less contained, and larger trees such as the brown turkey, magnolia, or Florida strangler fig trees have more of a tendency to dominate a space. These roots often trample or choke out other plants, and they can damage sidewalks, driveways and other objects in their paths.
The roots of a fig tree typically are woody and dense, and they generally grow near the surface, if not above it. They do best in warm, consistently dry climates such as their native Mediterranean and Middle Eastern habitats. Colder weather and thinner soil often impede the growth of roots. A fig tree will produce fruit in almost any condition, but it might not grow to its maximum size — or spread the roots that it needs to support its size — if its environment is less than ideal.
Gardeners who hope to plant fig trees in residential spaces often look for ways of naturally curbing root growth without depriving the plant of nutrients. In most cases, this involves confining the fig tree roots to a small space before moving the plant outdoors. Fig trees, like most ficus plants, do well as indoor potted plants. Beginning growth indoors can help the roots grow in a contained way, and it prohibits premature spreading. The roots will, of course, expand after the plant is moved outdoors, but usually not as dramatically.
Another option is planting young fig trees in prepared plots with built-in root restraints such as underground brick walls or planting liners. These restraints allow the roots to begin growing naturally but set up impediments to slow them down and keep them contained. Trees are usually able to grow all of the roots they need to support production with this kind of restraint, but the roots are kept close to the trunk. This sometimes also forces the plant to burrow down instead of out, which is far less invasive.
Regularly pruning fig trees, particularly when they are young, is another favorite way of containing root invasiveness. Pruning generally works only for gardeners who want small trees, however. Routine pruning is a part of caring for fig trees, because it helps the plants focus energy on fruit production and keeps the branches strong. To limit root growth, however, the trees must be aggressively pruned, which essentially stunts their growth.
There is nothing particularly wrong with invasive fig tree roots, except that they can disrupt other garden and landscape elements. People who are interested in planting fig trees on their property would be wise to carefully research the options before making a purchase. A bit of planning can save a lot of trouble.