Rosemary is a highly aromatic herb that is predominately used in cooking but is also grown for its ornamental value. Rosemary trees have become a familiar sight around the Christmas holidays when they are sheared or grown into various topiary shapes as tabletop centerpieces. Although attractive and decorative, these smaller sized container grown rosemary trees are frequently pot-bound, and need to be transplanted into a larger pot as soon as possible.
Choose a container that is 2 to 4 inches wider and deeper than the rosemary's current container, suggests master gardener Angela Chandler with Texas A&M University Extension.
Scoop a high-quality potting mix into the new planting pot for the rosemary tree to fill it approximately half full. The ideal potting mix should be fast-draining and contain both sand and either perlite or vermiculite. If the potting mix does not contain sand or perlite, pour out the potting mix into a bucket. Incorporate into the potting mix 1 part sand and either 1 part vermiculite or perlite. Adding these materials to the potting mix will ensure the best possible drainage for the rosemary tree.
Set the rosemary tree into a basin or bucket that contains about 4 or 5 inches of water. Let the rosemary tree soak for about 30 minutes. Remove the rosemary tree from the bucket and let the water drain away.
Turn the rosemary tree upside down. Keep your hand firmly at the top of its root ball while you wiggle the pot free from its root system.
Set the rosemary tree into its new planting pot. Hold the tree level and straight in the pot while you scoop in potting mix until the pot is approximately two-thirds full. Make sure the top of the root system will be at the same level at which it was previously growing. Once you are sure it's sitting at the right level, fill the planting pot with potting mix.
Place 2 to 3 tbsp. of a 5-10-5, or similar, water-soluble, root-stimulator plant food into 1 gallon of water. Pour the water into a bucket or basin. Place the rosemary tree into the water and let it soak up the water until you can see the potting mix become visibly wet.
Place the rosemary tree near a light-filled window and well away from heating ducts, which can dry the plant out rapidly. Place a saucer or dish under the rosemary tree to prevent the pot and any water from staining the surface it is sitting on.