How to Propagate Rosemary So You'll Always Have Fresh Herbs

Rosemary, Salvia rosmarinus, is a perennial staple in the herb garden with aromatic, pungent needle-like leaves.

Most varieties are evergreen and hardy in USDA zones 8 and 9 with some successfully overwintering in zones 6 and 7.

A good way to keep your rosemary plants going in colder zones, instead of replacing them annually, is to take stem cuttings during the growing season and propagate new plants for the following year.

Most rosemary varieties are moderate growers and require consistent pruning to get them into a full, bushy form.

To root cuttings in soil, you'll need a little patience since the process can take up to two months.

Follow these steps for a cost-effective method to increase your number of rosemary plants.

Take Cuttings

New tender growth from a mature rosemary plant roots most easily. Semi-hardwood growth is less reliable and takes longer but these types of cuttings can be rooted.

Woody cuttings won't grow roots so avoid taking cuttings from older stems of the plant.

Take cuttings 3 to 6 inches in length and cut just below a leaf node.

The consensus among growers is that shorter cuttings with greener stems yield a better rate of success than longer semi-hardwood cuttings.

Remove the bottom needles leaving three to five sets at the top of the stem.

Fill a Container

Several cuttings can be placed in a large pot or use smaller pots for single stems.

Propagating several cuttings at a time increases your chances for success.

Fill containers with moistened sand or a soilless potting mix. Make deep, narrow holes in the medium.

Treat With Rooting Hormone

Moisten the bottom of the cutting and dip it in rooting hormone and shake off any excess.

Place Cuttings in Planting Holes

Insert cuttings into planting holes taking care the rooting hormone remains intact on lower stems.

Needles should sit above the potting medium. If using one container for several cuttings, space them 3 to 4 inches apart.

Gently firm the medium around each stem to keep it upright.

Cover Pots With Plastic

Cover pots with large plastic bags. This creates a greenhouse effect which provides increased moisture and humidity to encourage root growth.

Provide Indirect Light and Warm Temperatures

Rosemary cuttings require plenty of bright, indirect light and warm temperatures of 70°F.

Keep soil moist but not soggy and remove plastic covering for an hour every day to increase air circulation.

Grow lights or fluorescent lights suffice for growing cuttings indoors. Or place your cuttings close to but not directly in a south-facing window.

Check For Roots

Be patient as rosemary cuttings can take up to eight weeks to form roots. Start checking around four weeks after planting by gently tugging on the cutting.

If you feel resistance, roots are growing. If the upper needles turn brown, dry, and drop, the cutting has failed.

Dispose of the cutting if you feel no resistance after eight weeks.

Caring for Rosemary Cuttings in Water

Rosemary cuttings also root in water. Take 3- to 6-inch softwood stem cuttings in summer and remove lower needles.

Place the cutting in a glass of clear, clean water with four to five sets of needles above water level. Replace water every few days or when it starts to get cloudy.

Cuttings generally produce roots in two to six weeks and can be transplanted into a standard potting mix once four roots 1/2 inch long are present.

Handle water-rooted cuttings gently as they are more delicate than those rooted in soil and vulnerable to transplant shock.

When to Transplant Rosemary Cutting

When a rooted rosemary cutting produces several sets of new green leaves, plants can be potted up into individual containers and moved into bright direct sunlight for six to eight hours daily.

When transplanting into the garden, wait until all danger of frost has passed and temperatures approach 70°F.

Allow several days up to a week to harden plants off.

Cuttings tend to grow slowly. If you plan to grow your rosemary seedlings out in containers, start with 4-inch pots.

Continue to pot up as roots fill the container increasing pot size by 1 to 2 inches. A deep 10-inch pot accommodates a mature rosemary plant.

Avoid overwatering and use clay or terracotta which helps keep soil on the dry side.

Cactus mix or good quality potting mix with added sand, grit, perlite, or vermiculite makes a well-draining planting medium.