A topiary of any kind can add interest to your home indoors or out, and when the topiary is an herb, it can also add rich fragrances to the air. The key with any topiary is to care for it regularly to keep it growing into the shape you desire. To train an herb into a topiary, simply start with the woody herb of your choice--whether it's rosemary, lavender, lemon-scented geraniums or African blue basil--and a pot the herb can grow in for two to three years.
Select the herb you want to grow and pick out a decorative pot in at least a gallon size. Fill the pot with potting soil up to an inch from the top and set your herb in the center of the pot, working the soil around to hold the herb securely.
Place a stake into the pot next to the herb so the stake and the main stem of the herb can run parallel. For taller herbs, use a longer stake.
Water the herb well and set the pot in a sunny location where the plant will receive at least six hours of direct sunlight each day. Don't overwater the pot, causing the soil to become soggy, but supply water any time the soil is dry to the touch on the top inch.
Fertilize the herb once a month with an all-purpose fertilizer, following the manufacturer's instructions and precautions.
Tie your herb's main stem loosely to the stake 3 inches from the ground and every 4 inches going upward as the herb grows taller as often as needed.
Cut away lateral branches with herb scissors from the main stem below the top 4 inches of the herb running all the way to the soil to leave behind only a long main stem and a full globe-like top. As the plant grows, you'll need to continue to cut new lateral branches.
Pinch off the top of the main stem when the herb reaches the desired height and clip the end inch of the branches that grow at the top to encourage the plant to fill out. As the plant grows fuller at the top, continue to clip away any stray branches that distort the circular shape.