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Planning Your Garden for Root Growth

Harvest cool season crops

Harvest cool season cropsThink about plant root growth when planning your garden. Be sure your planting beds contain plenty of organic materials such as compost and decomposed leaves to ensure strong root and plant growth.

Plant roots require loose, well-drained soil for optimal growth. Vegetable and fruit crops require strong, healthy roots to be most productive and most flavorful.

Soil rich in organic matter with good tilth—tilth means the soil is loose and crumbly and easy to dig–is essential for all plant growth and especially vegetables and fruits.

Good soil contains 50 percent air space. Air space in the soil allows for increased diffusion of oxygen. Oxygen is essential for the growth of both roots and soil microbes that enrich the soil. Carbon dioxide which is exuded by plants roots and must escape to the soil surface; this is made possible by soil with plenty of air space.

Preparing planting beds

When preparing your planting beds turn or loosen the soil and add organic matter such as aged compost to ensure the soil is loose and well-drained; this ensures there is plenty of air space for root growth. Compost-rich soil allows rain and irrigation water to easily reach roots, but also to drain down past roots ensuring plant roots do not drown.

Prepare planting beds that are both deep enough and wide enough for roots to grow. Good tilth should extend at least 2 feet down and 2 to 3 feet to either side of each plant. That does not mean each plant should be allowed that much space in the garden; roots of closely spaced plants—sometimes called intensive planting–can easily co-exist as long as they have good soil to grow through.

A mounded or raised bed is an excellent way to ensure plant roots get plenty go growing space. To make a raised or mounded bed turn the soil to a foot deep—about the length of a shovel or spade blade—and then add soil from the ground surrounding the new bed and compost to raise or mound the bed another 6 to 12 inches. A planting bed 18 to 24 inches deep will accommodate the root depth of most vegetable and small-fruit crops. A bed 24 to 36 inches wide will accommodate the width of crop root growth.

Examples of space needed for optimal vegetable crop root growth:(You will find the depth of these roots hard to believe; but these depths and widths of root growth are documented in the work of Nebraska researcher John E. Weaver. Seldom will we allow vegetable crops roots to reach their potential, and, of course, soil structure will affect root growth.)

  • Cabbage roots can grow to 2 feet deep and 2 feet out from the stem.
  • Lettuce roots can grow to 3 feet deep and 2 or more feet out from the plant stem.
  • Tomato roots can grow 3 to 4 feet deep and 2 to 3 feet out from the stem.
  • Sweet corn roots can grow to 4 feet deep and 4 feet out from the stem.
  • Carrots roots can grow to 6 feet deep and 2 feet out from the stem.
  • Beets roots can grow to 9 feet deep and 4 feet out from the stem.

Written by Stephen Albert

Stephen Albert is a horticulturist, master gardener, and certified nurseryman who has taught at the University of California for more than 25 years. He holds graduate degrees from the University of California and the University of Iowa. His books include Vegetable Garden Grower’s Guide, Vegetable Garden Almanac & Planner, Tomato Grower’s Answer Book, and Kitchen Garden Grower’s Guide. His Vegetable Garden Grower’s Masterclass is available online. has more than 10 million visitors each year.

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