Check with your local Cooperative Extension System/Service to find planting dates.

• Beets (Beta vulgaris) are cool-season plants that grow best at temperatures between 60° and 65°F. The optimum soil temperature for seed germination is 55° to 75°F. Beets prefer soil that is loamy or sandy. Hard clay soils prevent root enlargement. Beets require full sun and will not make good roots in partial shade. Protect beet seedlings from the wind because the young plants can rapidly dry out. Plant beets in rows 10 to 30 inches apart and place the seed ½ inch deep with about 2 inches between the seeds.
  (From Clemson's HGIC fact sheet on Carrot, Beet, and Radish)
• Radishes (Raphanus sativus) mature anywhere from 21 to 30 days from seeding, depending on soil and air temperatures during their growing time. For radishes, the warmer it is, the faster they mature. Radishes prefer cool and moist conditions for best growth. The optimum temperature is 50° to 65°F. Optimum soil temperature for seed germination is 45° to 85°F. Radish seed will not germinate when the soil temperature is above 95°F. Spring-planted radishes should be harvested early. Sandy to sandy-loam soils are best for radishes. Plant radish seed in rows 12 to 24 inches apart and place the seed ½-inch deep with about 1 inch between seeds. Radish seed can be broadcast in a 12-inch bed and then thinned when plants are in the one to two "true leaf" stage. Radishes are some of the fastest germinating seeds and should emerge in just a few days. Plant every seven to 10 days during the recommended planting periods for a continuous supply of radishes.
  (From Clemson's HGIC fact sheet on Carrot, Beet, and Radish)
• Plant spinach (Spinacia oleracea) in early spring to avoid high temperatures and long days, which cause the plants to bolt or form flower stalks. Soil temperature above 85°F will inhibit seed germination. Plant spinach seed in rows 1 to 3 feet apart, spacing seed 2 inches apart in the row. Plant seed ½ inch deep and firm the soil over the seed to help ensure germination. Seed can also be broadcast on 12 inch-wide beds. It is important to use new, fresh seed each year. Spinach seed that is more than a year old does not germinate well.
  (From Clemson's HGIC fact sheet on Spinach)