Soil Temperature & Root Growth

Root Anatomy

• Roots grow from the tip out. The root tip, or the root cap, is pushed through soil by the activity taking place in the cell division area directly behind it. Cell division increases the size of the root. Behind the area of cell division is the area that we normally associate with the word "root." In this, the largest section of the root, cells absorb water and nutrients from the surrounding soil using osmosis. When cells absorb water, they can grow, divide and push the root cap forward. When water is frozen and otherwise unavailable, root growth stops.

Annual Roots

• Annual plants live for one year. They are often found in borders and beds where their bright colors and long-blooming flowers provide decoration. These plants grow and bloom, but once their flowers fade, their life cycle ends and they will not reappear the following season. Sow annual seeds six to eight weeks before the last frost date.

  Once the ground warms to approximately 60 to 75 degrees Fahrenheit, the root system will begin to develop. Plant containerized annuals in the ground once the ground reaches temperatures within the 60-degree Fahrenheit range. Root systems establish best within these temperature ranges. Annual plants leave behind their roots systems after the plant dies. This is good, because the roots provide organic matter and help aerate the soil. The roots, however, stop growing once the plant dies.

Bulbs and Rhizomes

• Bulbous plants grow from extensions in their root systems. The bulb is actually stored energy that grows over the winter in warm climates. Cool season gardeners can assist in bulb storage and growth by overwintering bulbs outdoors. Place a loose mulch above the bulb bed. Bulbs are also overwintered indoors by placing bulbs in loose, moist sand. The temperature range should not dip below 30 degrees Fahrenheit.

  Rhizomes are roots that grow close to the surface and propagate by sending up shoots once the weather warms. Mulching outdoor rhizomes protects the roots over the winter. Below-freezing temperature dips harm rhizomes and have the potential to prevent shoot growth when the weather warms.

Considerations

• Trees are usually planted in late fall or in early spring, Their roots develop over winter whenever the temperature rises above freezing. This allows the root system to develop before the rush of spring growth. Roots and shoots do not grow simultaneously. Such activity will stress the tree. Shoot growth takes precedence since it is the shoot portion of the tree that creates food.

  While shoots develop, root growth lingers. Shoot growth, however, is limited by the amount of support it receives from the roots. A tree planted in late spring will not have had time to develop a dense root system before shoot development. When this occurs, growth is lackluster during the first season. By the second season, when the root system is better established, shoot growth resumes as normal.