Should You Divide Your Rosemary Plants? What Every Gardener Needs To Know

Dividing a perennial is a form of vegetative propagation that is not only considered good for a plant's health but also for producing new plants to add to your garden. Gardeners usually divide a plant when it starts developing new root clumps and shoots, which makes it difficult for the plant to acquire resources like water, sunlight, and nutrients due to overcrowding. Having said that, not all plants respond well to being evicted from their home base and shaken up like that. Your rosemary plant, for instance, being a woody shrub, falls into this category of perennials you should avoid dividing at all costs. In fact, dividing rosemary is not only fruitless but can also prove detrimental to the plant's life.

Rosemary (Salvia rosmarinus) is a beautiful, aromatic perennial that although often grown as topiary can become quite leggy when left unpruned. Woody shrubs have complex and well-developed root systems that can extend 1.5 to 3.5 times the size of their canopies. Since these roots perform the crucial life-sustaining functions of absorbing water and nutrients from the soil, they do not like being disturbed. In fact, even activities like digging, excavations, or adding soil can damage their roots due to suffocation, exposure, or a reduction in nutrient uptake. Rosemary shrubs are multi-stemmed when fully developed; their center is difficult to find, which is another reason they are not suitable for division.

Just because rosemary has obstinate, woody growth does not mean you don't have options for propagating this plant. Instead of propagating the plant through root division or bothering its woody stem (that is probably old enough to snap when you bend it anyway), you can make the most of its flexible young stems and grow a new plant from those cuttings. Consider only pest- and disease-free plants for taking your cuttings and make sure they are at least 4 to 6 inches long. Slice the ends with a pair of pruners at a sharp 45-degree angle for better water uptake. Get rid of the lower leaves. You can propagate the cuttings in water or sand depending on your preferences.

While the roots develop fastest in water, propagating in sand makes for stronger plants. If you like seeing results quickly, place the cuttings in fresh water. When you begin to see roots coming out of the cuttings in 2 to 6 weeks, transplant them into soil in a location that receives plenty of bright, indirect light. You need to avoid overwatering to keep your rosemary plants thriving all season long. Rosemary is generally hardy in most climates, but it is sensitive to frost. Nonetheless, you can still take cuttings in a cooler season like fall and expect to have healthy plants in late spring.