Many useful herbs are really easy to clone from cuttings. Many of the herbs are easy to start from seed as well, but you might have a hard time tracking down the seeds or just want to skip right to having a plant after a couple weeks of rooting in water.
Something I like to do is buy herbs that are in the grocery store. Certain ones root very easily so it is convenient and keeps me from having to buy the seeds again. Mint especially is one I like to get from the grocery store.
If you have a friend who owns one of these herbs you could ask them for a cutting.
Not all herbs root very well and there are rules to it. You want stems that are green. If they are woody or brown the roots will take longer to form or possibly never form.
My normal length for pretty much any cutting I intend to root is about 5-6 inches long. You want to be sure the cutting doesn’t have flowers or seeds and remove all leaves that will be in the water.
For chlorinated water you want to leave it sitting out for a day before adding any cuttings. I usually just used filtered water to make my life easier. Bottled water also works.
The cuttings do best near a window that gets sun though I had a grow room that was loaded with cheap compact fluorescent. If you go that route, you want to buy 6500k bulbs for ideal growing.
You should be rewarded with roots in about 2 weeks. I usually give them another week for good root establishment and then move them to pots or somewhere in my garden.
Basil This is pretty much a staple plant of any herb garden. It produces many seeds and you will end up with many extra plants around the area you had it planted. The only downside to basil is they are very intolerant to cold. They are also a slow start from seed really and in my experience it is just easier to get started from cuttings.
Mint, like peppermint or lemon balm– Mint is basically an invasive plant in the garden. My mother was overjoyed because her garden was full of mint and for some reason rosemary. She has little luck with keeping anything else alive because her life is pretty busy. If you get mint you will want to keep it strictly in a container, otherwise be prepared for it to take over your garden space. It is good for fresh use or can be dehydrated. I used to dehydrate it down to green flakes and add it to my tea mixtures for a little mint kick. It was very pleasant.
Oregano– In my house we had a lot of Italian style cooking so there was a lot of basil, parsley, and of course oregano which is more a southern Italy thing I’m told. The stem cutting should have 2 sets of leaves. This plant is slower to produce roots at about 4 weeks. The water needs to be tended to frequently so you don’t lose the plants to rot. Otherwise, it isn’t too hard to clone.
Parsley– Parsley is a harder one to start from cuttings. Some people add aspirin to the water and let it dissolve and then add the parsley to help keep water conditions good. Parsley is one I take a lot of cuttings for as I’ll plan for a lot of possible loss with some being successfully rooted.
Rosemary– This herb is one that will develop far fewer roots than the other herbs in this list. But once you have a decent clustering of roots you can plant it into a pot. Rosemary is a tricky plant in general that doesn’t like things too dry all the time but it also doesn’t want to be wet all the time. Getting the watering figured out is tricky for this plant at times is my experience.
Sage– Sage is a bit like the oregano where it is a very slow rooter. I really like sage for specialty chicken dishes.
Thyme– Thyme usually has browned stems. It is still a good plant to root in water so do your cuttings anyway. Once you have a good healthy ball of roots you can plant it into a pot. In a few weeks, it is ready to plant.
For further research, there are many videos on youtube you may want to explore. Such as the video below.