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Sat, Jan. 25

Backyard Gardener: Follow these strategies for growing root crops

“Detroit Red” beet planting 2019 (center), individual beet root with Swiss Army knife for size comparison (upper left), and initial photo of this beet planting — showing paper cups used to protect seedlings from cutworms and other pests (lower right). (Jeff  Schalau, University of Arizona/Courtesy images)

“Detroit Red” beet planting 2019 (center), individual beet root with Swiss Army knife for size comparison (upper left), and initial photo of this beet planting — showing paper cups used to protect seedlings from cutworms and other pests (lower right). (Jeff Schalau, University of Arizona/Courtesy images)

Root crops are vegetables that are grown specifically for their edible roots. They are considered cool season vegetables and do their best growing in early spring or late summer and fall. These vegetables include beets, radishes, carrots, turnips, parsnips and rutabagas.

People sometimes struggle growing root crops, and there are a few production strategies that I’ve learned over my years of vegetable gardening.

Most root crops (except salad radishes) are biennials. Biennial root vegetables grow lots of foliage the first year and store carbohydrates produced by those leaves in their large roots. The second year, they spend what they stored up by producing flowers and seeds. We seldom allow these root crops to go to seed because we usually harvest them for their roots. However, it is fun to allow one or two plants to produce seed and observe the process. The flowers on these plants may surprise you. Carrot flowers also attract many beneficial insects including parasitic wasps and flies.

Root crops prefer full sun (at least eight hours of direct sun). Your garden soil should be prepared as you would for any crop by incorporating organic matter (compost) and appropriate nutrients as indicated by a soil test. There are many ways to add organic matter, which include using animal manures, cover crops/green manure or alfalfa pellets. Small additions of phosphorus fertilizer applied to the root zone often increase production in Arizona soils.

When growing root crops, it is also critically important to incorporate organic matter and loosen the soil to a depth of 12 inches. Never till soil to the extent it loses its structure and is broken into single grains. Similarly, you should not till or trample wet soil as this causes the soil to lose structure and become compacted.

Root crops also perform poorly in gravelly or clay soils. Check your soil for obstructions like pieces of wood, rocks or debris, and remove the larger pieces. Carrots can become misshapen and crooked when their roots encounter hard objects. Additional organic matter may be necessary for clay soils.

All root crops can be planted in spring and harvested during summer. I try to plant my root crops in mid-summer after I have pulled out my edible pod peas and garlic. However, I also like to grow carrots and beets into the fall. As the weather cools in fall and early winter, the roots become sweeter.

These plants can tolerate cold temperatures, and the roots are can be harvested through November and beyond. Parsnips should be in summer and left in the ground until two to four weeks of near-freezing temperatures to sweeten properly.

If I am sowing seeds of beets or chard, I soak the seeds for 24 hours in warm water to aid germination. These seeds are actually a cluster of seeds in a small dried fruit. Carrot and turnip seeds can be planted in late summer for a fall crop. When I plant in summer, I anticipate losses from cutworms and other insects in addition to rabbits, rodents and birds. For cutworms, I use waxy paper disposable cups with the bottom removed to protect seedlings. Floating row cover is a good barrier to prevent rodent and bird losses.

When growing root crops, it is very important to thin the seedlings to provide growing space. I like to have my carrots about four to six inches apart, beets and turnips should be about six to eight inches apart. If not thinned adequately, these plants will not produce as expected. Beets and turnips also have edible leaves. If growing these crops for roots, I recommend not harvesting too many leaves as this decreases the growth of the root. Thinned plants can be eaten as greens or plant another area that will be grown specifically for leaves. Harvest roots when they are sweet and mature.

Many Backyard Gardeners focus on summer crops, but over time I have learned how to use my space for year-round production. It requires some organization as to planting dates and crop rotations. However, in the end, the result is a greater variety of fresh food and variety over the course of the entire year. So, plan and select your root crops for next year. It’s also time to plant garlic, lettuce and cover crops right now! Visit the online edition for additional resources (see URL below).

You can follow the Backyard Gardener on Twitter — use the link on the BYG website. If you have other gardening questions, call or email the Master Gardener help line in the Prescott (928-445-6590/ or Camp Verde (928-554-8992/ and be sure to include your name, address and phone number. Find past Backyard Gardener columns or provide feedback at the Backyard Gardener web site:

Jeff Schalau is county director/agent for Agriculture & Natural Resources, Yavapai County and interim county director, Mohave County University of Arizona Cooperative Extension.

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