To give rosemary seeds their best chance at thriving, it’s best to start growing rosemary indoors. Fortunately, for those living in the tropical areas (like Singapore), you are able to grow rosemary anytime of the year. For others, since rosemary seeds are slow to germinate and grow, start them three to six months prior to growing season. Rosemary seed germination rates can be as low as 30 percent at times, so it’s best to start more seeds than you expect to plant. Our premium Potter Rosemary seeds are perfect for you.
- Choose a container. You can use small pots or a ziplock bag, but your best choice is to purchase a seed-starting tray with a plastic humidity dome.
- Prepare a seed-starting mix. Ensure that the soil you use has good drainage. You can create your own mix with equal parts perlite and peat moss or purchase a sterile, soilless seed-starting mix. Add some water to moisten the mix before adding it to your container. Otherwise, place your seeds onto a wet tissue and seal them inside a ziplock bag.
- Add the rosemary seeds. Sprinkle three to four seeds on top of the seed-starting mix. Cover the seeds with a small amount of mix, but not so much that they don’t get sunlight. Rosemary seeds require light to germinate!
- Lightly water, then cover the container. Mist the seeds with water using a spray bottle, making sure the surface is moist but not sopping wet. This helps settle the seeds into the mix. Cover the container with the plastic dome or plastic wrap.
- Store in a sunny, warm location until germination. Place the seed-starting tray / ziplock bag somewhere that receives plenty of direct sunlight. A heat mat and an indoor full-spectrum light can be used if you’re unable to find a warm, sunny area. If the surface of the seed-starting mix appears dry, remove the plastic cover and lightly mist with water until moist. The germination process typically takes two to four weeks.
- Once seedlings appear, remove the plastic cover. When the rosemary seedlings emerge from the soil, place the seed-starting tray in a shallow water tray. Water will seep up into the soil through the container’s drainage holes. Keep the seedlings in direct light.
- Transplant the seedlings. Once seedlings are three to six inches tall, transplant them outdoors. Plant rosemary seedlings in compost-rich soil with good drainage. Choose a location where they receive six to eight hours of direct sunlight each day. You can transplant your rosemary seedlings into a garden bed or, if you want to bring the plants inside during cold winters, a pot.
Source: https://www.masterclass.com/articles/how-to-grow-and-care-for-rosemary#how-to-grow-rosemary-from-seed-in-7-steps