Spacing

• Though carrots and tomatoes are companion plants, tomato plants can stunt carrots if planted too closely together. Plant tomatoes 15 inches apart from carrot and other tomato plants. Space carrots 1 inch from other carrot plants.
  
  

Soil

• Carrots and tomatoes grow best in loose, well-draining soil. Both vegetables grow best in soils low in nitrogen, but high in phosphorous and potassium. In high-nitrogen soils, carrot roots will fork and be misshapen. Tomatoes will produce less fruit if over-fertilized with nitrogen. For best results, conduct a soil analysis before amending the soil.
  
  

Water

• Tomatoes and carrots have similar water requirements. Water both vegetables to maintain moist, but not soggy soil. Water in the morning hours to allow time for the plants to dry before nighttime temperatures drop. It is better to water the plants thoroughly two to three times weekly than to water lightly each day. Water until the soil is moist, 6 inches below the surface.
  
  

Weed Control

• Weeds compete with carrots and tomatoes for moisture and soil nutrients. Carrots are shallow rooted and can be damaged easily from cultivation. It is best to prevent weeds through mulching. Apply 2 inches to 4 inches of organic mulch, such as hay, straw, grass clippings or newspaper around plants.