Root Systems Basics Every Gardener Must Know
The “root” is generally defined as the underground portion of a plant which anchors the plant to the soil and absorbs water and minerals. Knowing the way roots are formed and grow can help you understand where to place a plant and how to prepare the planting area. When you purchase a tree, shrub, perennial or annual from a nursery, it will likely come in a plastic pot (sizes typically range from 4-inch on up to 5-gallon). Once you have removed the root ball from the pot, evaluate whether it is healthy-looking or stressed.
Healthy roots will be evenly distributed throughout the block of potting soil. Unfortunately, you’ll often discover root-bound masses that have circled the base of the round or square-shaped pot. Most roots will need to be loosened up and teased out of their tight clump. You can use a good pair of pruners to slice into the roots, breaking up the clump in at least four sections around the root ball. Pull away excess (often dry or weak) root ends and spread the remaining roots away from the crown of the plant, sunburst-style, so when planted they will come in contact with the soil. When tangled roots are cut off, the plant will be rejuvenated.
Trees and shrubs may be sold in ball-and-burlap packaging. Sometimes the wrapping holds roots packed in a potting soil-like growing medium or in sawdust. Be sure to keep the ball-and-burlap package well-watered until planting (do not allow it to dry out). If the wrapping material on a bare-root plant is plastic or non-biodegradable, be sure to remove and discard it at planting time. Do not leave any of this material in the planting hole or root zone.
Types of root systems include:
Fibrous Roots occupy a large volume of relatively shallow soil area around the base of the plant. The “system” of roots consists of many thin, profusely-branched roots—similar to grass roots. These roots remain close to the surface of your garden (generally in the top 12-to 18-inches), capturing water and nutrients quickly before they move through to lower levels of soil. Considering the way fibrous roots spread may influence the quality and extent of soil preparation in the area surrounding your planting hole.
Tap Roots are formed by one or two long roots that grow quickly and move straight down into the soil to draw moisture and nutrients from deep within the earth. This type of root system serves particularly well as an “anchor” to hold the plant in windy or exposed sites. Many conifers are anchored by deep tap roots, although these roots will develop horizontal branches. A carrot is essentially the (edible) tap root of the plant.
While not a root system, it’s important to understand how plants with Rhizome and Runner systems grow, as well. A rhizome is a modified stem that grows underground; as it spreads, new plants are created. Likewise, a runner (or stolon) is a modified stem that sends out shoots above ground to expand its reach. If a plant spreads in such a manner above or below the soil, it can quickly grow to occupy more of your garden than you originally planned. Determine if the plant you choose grows by runner or rhizome. Plants like strawberries or vinca have modified stems that rapidly spread in this manner.
Understanding a plant’s root system will help you to properly plan and prepare the intended planting area.