What Causes My Carrots to Be Bitter?

Carrots (​Daucus carota​ subsp. ​sativus​) are one of the easiest vegetables to grow, but several things can cause carrots to be bitter. Carrots are sweet root vegetables that grow best in the early spring when temperatures are cool. Warmer temperatures can be one cause of a bitter carrot, but disease, storage and harvesting issues can also be to blame.

Carrots grow best in temperatures between 60 and 65 degrees Fahrenheit because they are cool-season vegetables. Carrots will have a bitter flavor when temperatures reach more than 80 F during the growing season. Carrots contain sugars, which give them their signature sweet flavor, and terpenoids, which create the carrot flavor. If carrots grow in warmer temperatures, the sugars in the carrots may not have formed or the terpenoids may remain high, leading to the bitter flavor.

Plant carrots early in the season to give them plenty of cool weather for maturing. You can sow carrot seeds three to six weeks before the last frost in your area. You can also sow carrot seeds late in the summer for a fall harvest. When temperatures begin to warm outdoors, mulch the carrots to help keep the soil cool. For best results, harvest the carrots as soon as possible.

Aster yellows disease can form on carrots due to the aster leafhopper. When the leafhopper feeds on infected plants for an extended time, its saliva becomes inoculated with the pathogens and can spread the disease as the insect moves from plant to plant. The carrot leaves may begin to turn yellow, the carrot growth may slow down and the carrot roots may become bitter. The roots will also have fine hairs and lack color.

Manage the disease by removing infected carrots and control the insects by covering the crops with mesh fabric to exclude leafhoppers. Removing weeds from the garden can also help because they may contain the disease.

Pulling the carrots out of the ground while they are young and tender may result in a bitter or soapy flavor. Different varieties of carrots can have a higher amount of terpenoids, which will form before the sugars in the carrot. When you harvest the carrots while they are young, they may not contain enough sugar, which results in the bitter taste.

Harvest the carrots when they are 1/2 inch in diameter and continue to harvest them throughout the growing season only when they are mature. Most carrots reach maturity within 60 to 70 days after you plant them if the growing conditions are right.

After you harvest carrots, they need to be stored properly to keep them fresh. Carrots are best stored in the refrigerator crisper drawer away from apples and pears. The release of ethylene gas from these fruits can cause the carrots to have a bitter taste. Trim the tops off the carrots and keep them in perforated plastic bags in the refrigerator for three to four weeks. The green tops only last for two to three days on the carrots and need to be stored separately from them.