Q. What causes turnips to fail to make large roots?
A. Like radishes and other bulbing crops, crowded turnips will fail to enlarge. Turnips also require a moderately fertile soil and adequate moisture to grow large, fleshy roots. For good size bulbs, space turnips 2 to 3 inches apart. Plant in the spring as soon as the ground can be worked. For a fall crop, plant when daytime temperatures average below 80 degrees F. In many areas of Texas, planting can begin in early fall and continue until about 5 to 6 weeks before maximum daytime temperatures average 80 degrees F.
Q. Are there varieties of turnips grown just for the tops and not their enlarged roots?
A. Yes. The varieties Crawford and Shogoin are grown primarily for their tops and usually fail to make large, high- quality roots.
Q. What causes my turnip greens to often have a bitter and pungent flavor?
A. Conditions which result in slow growth or stress of the turnip plant will often cause the leaves to have a bitter, off- flavor. This condition is prevalent when turnip leaves mature under high temperatures combined with unfavorable growing conditions.
Q. My plants appear to be stunted and have small, round galls on the roots.
A. This is root knot nematodes. They are controlled by rotation and summer fallowing. Root knot is a species of nematode which causes galls or swellings on plant roots. It restricts the uptake of nutrients from the root system to the foliage, resulting in a yellow and stunted plant. Root knot lives in the soil and can survive on a number of weed and vegetable crops. It is best controlled by planting a solid stand (close enough for root systems to overlap) of marigolds three months before the last killing frost of fall and/or planting cereal rye (Elbon) for a winter cover crop. Cereal rye should be shred and tilled into the soil 30 days before planting a spring crop.
*Refer to mustard for other diseases that are associated with turnips (page 41).
Q. How do you control aphids or plant lice on turnips?
A. Aphids can be easily controlled with an insecticide such as malathion. Begin applications the first time the insects are observed and repeat periodically.