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Growing Rosemary in Winter
submitted by Sarah Browning, UNL Extension Educator
Rosemary, Rosmarinus officinalis, combines ornamental beauty and the usefulness of a culinary herb in one attractive plant. Rosemary grows as a woody, evergreen shrub, and in its native Mediterranean region they can easily grow to a height of 4-6 feet. However, they seldom reach that height in Nebraska gardens.
The plants have slender, needle-like foliage, with either a dark green or gray-green coloration. The foliage is fragrant, and plants produce flowers in spring and summer that are light blue, pink, or white.
However rosemary is a very tender perennial herb, and so is usually grown as an annual in Nebraska. Under normal garden conditions plants are hardy to Zone 7, and possibly to Zone 6 with winter protection. Occasionally in eastern Nebraska, hardiness zone 5, gardeners can find just the right spot that provides extra warmth in winter, protection from wind, and well-drained winter soil conditions that will allow rosemary to survive if they are given extra winter protection.
Their roots are more cold-hardy then the top-growth, so protection must be provided for the branches and foliage to survive. However, the biggest threat to winter survival is wet, poorly drained winter soil.
In the summer garden, rosemary prefers a sunny, sheltered location with very well-drained, dry, and almost gravelly, slightly acidic soil. For their best winter survival, rosemary should be planted close to your house on the south or west side so that plants benefit from retained and reflected winter warmth.
Make sure plants are protected from strong winter winds. This can be done through the use of rose cones placed over the plants in late November. Also mulch the roots with 5-6 inches of wood chips to provide additional root protection.
‘Arp’ is a common cultivar, originated by Madalene Hill from Arp, Texas, and is one of the most winter hardy types (Zone 6). It has light blue flowers on upright 3’ tall plants.
Rosemary As A Houseplant
If you don’t want to take the chance that your rosemary may not survive outside, then plants can also be grown as houseplants. Simply dig up your plants and repot them into containers for growth inside during winter. Remember to use a potting soil that contains perlite and/or vermiculite to improve drainage. Or create your own potting soil by mixing 2 parts peat-based soil with 1 part clean sand.
Provide plants with a bright, sunny window during winter. Normal indoor temperatures are fine during winter, but rosemary would also be happy in cooler conditions 55-50 F if that is available. Water as needed to keep plants evenly moist to slightly dry.
Another option, if you don’t have room inside for rosemary in containers, is to harvest long stems or whole plants before frost and hang them upside-down in bunches in a warm, well-ventilated location to dry. Once dried, strip leaves from the stems and store them in tightly covered jars in a dark, cool location. If moisture condenses inside the jars, more drying is needed.
University of Nebraska-Lincoln Extension in Lancaster County is your on-line yard and garden educational resource. The information on this Web site is valid for residents of southeastern Nebraska. It may or may not apply in your area. If you live outside southeastern Nebraska, visit your local Extension office
Contact Information University of Nebraska-Lincoln
in Lancaster County
Web site: lancaster.unl.edu
444 Cherrycreek Road, Suite A, Lincoln, NE 68528 | 402-441-7180