YC and I are attempting to grow about 200 rosemary plants from cuttings (more on exactly why we’re doing that later)… Last summer, I grew a few plants on accident when I took cuttings and left them in a glass of water with some other herbs and flowers for about a month. The flowers all died, but the mint and the rosemary rooted, and now YC has a fairly good sized rosemary plant in his elevated garden beds, an exact clone of the rosemary in my garden. For the past few months, I have been trying, mostly unsuccessfully to root some rosemary – intentionally this time. Finally – FINALLY – I successfully rooted a dozen rosemary plants from cuttings (a 100% success rate with the method I used!). Now, I have about 60 more cuttings, attempting to root them by the same successful method. Today, I’m sharing a few tips that I’ve learned this spring for rooting rosemary from cuttings.
1. Take small cuttings of new growth. I have tried all lengths and variations of new (green) stems of rosemary versus the older, woody (brown) stems. The new stems root much better. (In fact, the woody brown stems did not root at all.) Also, don’t be afraid to take small cuttings. My intuition was to take cuttings that were 3-4 inches long, but I had less success with these. It works better if you take cuttings that are 1.5 to 2.5″ long. I think that this might be because the new cutting has fewer leaves and less stem to support and feed.
2. Root the rosemary in water. I did a side-by-side comparison, attempting to root rosemary in water versus peat pellets. The rosemary that I rooted in water had a 100% success rate in about 10-14 days. The rosemary that I attempted to root in soil had a 0% success rate, and although the cuttings are still green, they show no signs of root hairs, even after 3 weeks.
3. Root rosemary in wine glasses. I honestly haven’t the faintest inkling why this works, and perhaps it is very unscientific. But I have now attempted rooting in a variety of glasses – tall ones, short ones, mason jars, etc. The one that works best is the wine glass. It may be because the shape of the wine glass helps to trap some evaporating moisture? Or it keeps all of the cut ends in a very little bit of water at the bottom of the glass while letting the majority of the cuttings remain out of water, thereby preventing rot? Either way, this is what worked for me.
4. Keep the water level low. As I mentioned above, the shape of a standard white wine glass (mine are from Ikea) allows for all of the cut ends to be concentrated at the bottom of the glass. You don’t need more than a half inch to an inch of water in the bottom. Even an inch might be a little much. Just check it periodically to make sure that you’re cuttings haven’t run out of water and replenish when necessary.
5. Use water that has sat out over night in a glass. My dad tells me that by keeping a glass of tap water out overnight or at least for several hours, you allow the chlorine to evaporate off and that this is good for the plants. After attempts with both fresh tap water and tap water that has sat out, I have had greater success with the tap water that has set out over night.