Ask Henry!

Submitted 2 years ago
Created by
Henry Homeyer

How to get a good supply of rosemary plants - and more

Matt writes, “I am a young gardener and am still in school. For the past few years, I have started my tomato, pepper, and eggplant seeds during my March spring break, while I was home. My family has a wedding at the end of the year and we want to hand out rosemary seedlings/plants to the guests. Do you have any suggestions for starting rosemary from seed?”

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Well, Matt, starting rosemary from seed is tricky. The seeds must be very fresh in order to germinate, and most packaged seeds have a very low germination rate. Even professional growers rarely start rosemary from seed. But there is an easier way to get a good supply: root them from cuttings.

Snip off new growth for rooting

I called a specialist on herbs, Sarah Milek of Cider HillGardens in Windsor, Vermont. Sarah suggested cutting stems off a mature plant and rooting them in water. You need to get fresh new growth, which should be plentiful on rosemary plants right now – they are starting their spring growth. Cut off a stem, then re-cut it half an inch or more up the stem, preferably making the cut beneath the water's surface in a bowl of water. 

Lower leaves have been stripped and are stems are ready to go in water

Don’t select woody brown stems, but fresh, light green ones. Strip off the leaves on the lower part of a stem and submerge at least a couple of inches in water, and place the vase in an east-facing window that gets morning, but not  afternoon sunshine. Sarah suggests using a brown or blue glass jar or bottle for rooting (to diminish the light intensity on the rooting portion). She said that rosemary cuttings root easily, and once they have roots, she pots them in a commercial potting mix in 4-inch pots.

Ready for the window!

Matt also asked about electric heat mats: “My thought is that adding heat from the bottom of the germinating seeds and growing seedlings could invigorate them quickly and encourage stocky and sturdy growth. Do you think adding heat could be the solution to avoiding spindly seedlings?  

Heat mats are good for getting seeds to germinate more quickly. Once they have started to grow you should unplug them. Heat yields fast growth, and you want stocky, sturdy growth. For that? Buy some fluorescent lights and hang them 3 inches over the plants. Click here for an article about how to make a simple plant stand. And keep the room cool, especially at night. Never leave lights on all night – growing plants need rest as much as growing young people!

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