How Does a Larkspur Tolerate a Frost?

Hardiness

• The exact hardiness, or cold tolerance, of larkspur differs among varieties, but it typically tolerates cold well. Varieties like "Bluebird," for instance, are cold hardy down to Zone 3, about negative 35 degrees Fahrenheit. The rate at which larkspur goes through acclimation -- the increase of plant tissue hardiness in response to decreasing temperatures -- changes each year and varies depending on the plant's health. Larkspur has a relatively quick rate, which contributes to its hardiness.

Tolerating Frost

• Like other plants, larkspur tolerates a frost by going into dormancy, a type of phenotypic plasticity. During this time, larkspur forms no new growth. Instead, it goes into a resting period in which no photosynthesis, the conversion of light to energy, takes place. Larkspur's flowers and foliage dry up at the start of this period. No new growth takes place until temperatures begin to warm.

Preparation

• Larkspur needs preparation for enduring frost but should be cut to 1 to 2 inches above the soil line after the first killing frost. If well cared for, larkspur lasts two to four seasons, depending on the variety, climate and its overall health. Divide larkspur into clumps every three to four years to allow these perennials to remain vigoruous.

Preferred Conditions

• Larkspur thrives in climates with cool, moist summers. It does not tolerate extreme heat well. It typically enjoys an area in full sun or partial shade and rich, well-drained soil. Taller varieties need an area with wind protection and should be staked. Planting in spring allows larkspur enough time to establish and flower during the summer.