How Long To Boil Tomatoes. Bring to a boil over high, stirring until sugar dissolves. Canning tomatoes is a great way to preserve your tomato harvest to enjoy it later during the winter holiday season.

Bring to a boil over high, stirring until sugar dissolves. Bring to a low boil, stirring occasionally to dissolve the sugar and salt. Pour vinegar mixture over green tomato mixture in jar.