Rosemary is a wonderful herb that is popular as both a garden herb and a culinary favorite. Unfortunately for those who live in the cooler zones (zone 6 and lower), rosemary is not winter hardy, so it must be treated as an annual or you have to bring the herb inside for the winter and try to keep it alive - which is not easy.
For those who have problems keeping rosemary alive from one year to the next, and those who like to have lots of rosemary in the garden, growing the rosemary from seed each year is a practical option.
The seed takes a while to germinate so you need to start it about three months before the warm weather arrives. Place the seed onto a well-drained base such as sand, vermiculite or very light potting mix. Cover the seed with a little more mix, water lightly and place the container in a warm location or onto a heat mat. Cover the container with plastic wrap until you see the seeds starting to emerge. As soon as you see the tiny rosemary plants starting to grow, it is important to give them a good light source and a warm environment. Do not expect germination of all the seeds as rosemary has a much lower germination rate than some other popular herbs such as basil.
Allow the rosemary to grow inside or in a sheltered area outside, until they are about 3 inches high and sturdy enough to handle. If the weather is warm outside, the seedlings can be put into the garden where they will continue to grow. Alternately, pot the seedlings into larger pots so that you do not have to disturb them if you want to bring them indoors for next winter. Use pots with several small rosemary plants to make rosemary topiaries. The small plants can easily be trained onto a hoop or other shape.
In warmer areas, zone 7 and above, your rosemary plants will be large enough to survive outside and give you pretty blue flowers early next year. Rosemary that is brought indoors will also flower in late winter to give you some winter interest when you really need it.
Rosemary requires only sunlight, good drainage and ample air circulation. A sandy, well-draining soil and 6 to 8 hours of full sunlight daily will have the plants off and running in no time.
There is little need to fertilize the plants. A basic 5-10-5 fertilizer applied in the spring and perhaps a foliar spray mid-season will keep the plants healthy and happy.
Where winters are somewhat severe and sustained temperatures are well below 30 degrees F., rosemary plants will have to be brought indoors for the coldest months.
Snip off sprigs of rosemary all summer and into the fall and winter as needed. Where winter temperatures are severe and bringing plants inside is not an option, rosemary can be easily dried and stored.
Simply bundle sprigs and hang them inverted in a warm, airy place. A covered porch works fine. Once dried, store the sprigs or stripped off leaves in sealable plastic bags or jars. They will keep until next season’s crop is ready to harvest.