If basil is not the most popular culinary herb in the United States, it certainly comes in near the top of the list. The basil leaves used in cooking grow on the basil plant (Ocimum basilicum). This small shrub can add scented greenery to a favorite corner in your garden. It also makes a happy container plant in a sunny kitchen. Instead of buying a potted plant from a garden store, you can grow your own basil plant by rooting a cut stem from an existing plant.
Take your cuttings from a vigorously growing outdoor basil plant. Using a piece of cut basil from your grocery store's produce section is less reliable, because they are not always fresh enough to root. To take the cuttings, wipe pruning shears with rubbing alcohol (this disinfects the shears and prevents the spread of plant diseases ) and snip off a 4-inch growing tip of a healthy basil branch. Make the cut right below a spot where the basil leaves attach to the stem; this is where the cut piece has the best chance of growing roots.
Rooting Cuttings in Water
Rooting basil cuttings in water is easy. Pluck off the leaves on the bottom two-thirds of the basil stem to prevent them from rotting under the water. Place your basil cutting into a very small cup or jar. The jar should be shallow enough that a third of the basil cutting extends out of the cup, allowing your basil to breathe properly. Fill the jar with water, and place it in a sunny location, such as on an east- or west-facing windowsill. Change the water once a day to prevent bacteria buildup. You should see roots developing within a week or two.
Rooting Cuttings in Potting Mix
Use an 8- or 10-inch pot with drainage holes in the bottom. Fill the pot with a sterile, soilless potting mix, such as one made with vermiculite or perlite. Strip off the leaves on the bottom third of the cut basil stem. Dip the cut end of the stem in a rooting hormone powder; though not absolutely necessary, this can increase how quickly the cutting takes root. Use a pencil to poke a hole in the potting mix deep enough for a third of the length of your piece of basil. Insert the cut end of the basil stem into the potting mix, and tap down the soil around it. Mist the pot with water to moisten the top few inches of potting medium. Place the pot on a sunny east- or west-facing windowsill. Repeat the watering once or twice a day, or as necessary to keep the cutting moist.
Once the roots on your water-rooted basil plant measure approximately 1/2 inch long, or once your potted basil cutting has grown several inches high, it's ready for transplant. You can either move your basil into a 1- or 2-gallon pot filled with soilless potting mix, or you can place your basil plant directly in the ground. Whatever method you choose, its final home should receive full sun. If you place your basil outdoors, only do so after the last frost date in your region to avoid frost injuries to your fragile new basil shrub.