A fibrous root is a type of plant root. In plants with a fibrous root system, the roots are all more or less the same size, and they look like fine, branching hairs which have grown to create a dense mat. This type of root system is extremely common, especially among grasses and wildflowers, and it has a number of advantages for the plant. Many people have experienced fibrous roots if they work in the garden.
When plants start growing, the first root they put out is known as a radicle. The radicle is a large, thick root which is designed to get the plant established and anchored so that it will be able to absorb nutrients. Plants with fibrous root systems have radicles which eventually die back, allowing fibrous roots to project from the stem and into the soil. Taproots, by contrast, develop directly from the radicle, creating a single large, thick root which anchors the plant in the ground. Classically, fibrous roots can be found projecting from taproots to gather nutrients for the plant.
One of the advantages of a fibrous root system is that it can be extremely useful in erosion control, because the roots help to hold soil in place. The roots can also trap moisture for the plant, and their wide spread ensures that the plant gets plenty of access to nutrients and water. Fibrous roots also hold a plant firmly in place so that it cannot be disturbed by heavy weather, animals, and other forces.
These advantages can also prove to be disadvantages for gardeners, when a plant with fibrous roots is undesired. These plants can be difficult to pull out and eradicate because they grip the soil so firmly, and the plant will regrow if the roots are not fully removed. Weeding such plants is also messy business, because they tend to pull up large chunks of soil and other substrate materials such as gravel and decaying organic material.
Fibrous roots like to spread out, which can be a big problem in container gardening. Plants with these types of roots have a tendency to get rootbound as the roots start to pack the container the plant is grown in. As the roots continue to grow, they will mat and fold back on themselves, creating a tight rootball which deprives the plant of nutrients and makes the plant difficult to transplant. A fibrous root system can also be endangered when people dig around the parent plant, as people may sever the roots without realizing it.