Rosemary (Salvia rosmarinus) is a well-loved garden herb in the mint family. It has been known as the herb of remembrance since ancient times when Greek and Roman scholars would wear rosemary garlands in their hair to strengthen memory, and families would throw sprigs of rosemary into graves to signify remembrance of the departed. Its fragrant leaves are used to flavor soups, stews and sauces. Its woody branches can be used for barbeque skewers.
Rosemary is an evergreen shrub that reaches a mature height of about 4 feet. It produces blue flowers in spring and summer, though flowering can be unreliable. Rosemary is native to the Mediterranean, and cannot survive winter temperatures below 20 degrees Fahrenheit. It is usually grown as an annual in central Washington, or grown in pots that can be moved inside during the winter.
Although it is a popular garden herb, starting new rosemary plants can be difficult. The seeds are slow to germinate, requiring 14 to 21 days or more, and usually fewer than half of the seeds will germinate at all. Seedlings grow slowly, and should be started at least three months before the last spring frost.
If you want to try growing rosemary from seeds, press the seeds into a moist soilless starting mix and sprinkle a bit of the mix lightly on top of them. Don’t cover the seeds completely, because they need light to germinate. Use a spray bottle to mist the seeds with water to settle them, and place your starting tray in a warm place that receives at least eight hours of light every day. It’s a good idea to put a heat mat under your starting tray, since optimum soil temperature for germination is 80 to 90 degrees Fahrenheit.
If you have access to a mature rosemary plant, you will find it easier to start new plants from cuttings. This should be done after flowering has finished and plants are actively growing. Use a sharp plant clipper to snip off a few healthy, well-developed stems about five inches long. Not all cuttings will root successfully, so take 10 to 20 percent more than you need. Carefully pinch off the needles from the lower three or four inches of the cuttings. Place the cuttings in a jar of water and keep them in a warm place with good sunlight. Change the water every few days. It will take about four weeks for roots to form. If the needles turn brown, the cutting has failed and should be discarded. Once roots have formed on your cuttings, transfer them to pots with clean potting soil and grow them for a few weeks until a strong root system has developed. Then they can be transplanted into your garden, or you can keep them as potted plants.
Cuttings can also be started in moist, soilless seed starting mix. This takes more preparation that simply putting cuttings in water, but I have had a higher success rate with this method. Rooting will be faster if the ends are dipped in rooting hormone. Rooting hormone products come in powder, liquid or gel forms, and can be purchased at many garden stores. I prefer the gel form because it is easier to use.
Rosemary may be a challenge getting started, but it is a lovely plant for your home or garden. Consider giving it a try the next time you are looking for a new herb to grow.
A WSU Master Gardeners of Chelan County column appears weekly in The Wenatchee World. Connie Mehmel is one of four columnists featured. To learn more, visit wwrld.us/cdmg or call (509) 667-6540.