When choosing vegetables for a Garden, consider some varieties that stand out for their adaptation to Colorado’s climate
Cool season vegetables are always difficult to grow here because of temperature fluctuations in the spring. Many respond to high temperatures by bolting, or producing a flower stalk. Some varieties may resist bolting and are better bets for planting in the Front Range area.
Romaine lettuce types hold up better than loose-leaf and head lettuces when weather turns warm. Sierra, a large, flat-leafed type of lettuce with a purple tinge, did not bolt in tests held by Colorado State University. Though not tested, Jericho, a new romaine lettuce from Israel, should be considered. It is reported to retain its sweet flavor and crisp texture better than some other lettuces in hot weather.
Of the five Chinese cabbage varieties tested, Optiko did not bolt as fast as the others. In previous years, two other varieties that showed better adaptation are Two Season and Yoko. Two radicchio selections, Firebird and Medusa, did not bolt in previous tests, but both bolted the following season.
For more information, see the following Colorado State Extension fact sheet(s). http://www.ext.colostate.edu/ptlk/1804.html