Native to Australia, bottle brush trees (Callistemon) bear vivid red flower spikes that resemble the bottle brush, giving the plant its common name. These small trees grow up to 15 feet; dwarf cultivars are available that average 5 feet. Since England's climate is much colder than that of Australia, bottle brush plants can receive frost damage and die if not offered protection. British growers should grow dwarf callistemon trees in containers and bring them indoors during winter to give the trees the best shot at survival.
Cut a piece of mesh screen to fit in the bottom of a 5-gallon pot. This prevents soil from washing out of your container.
Fill the container halfway with well balanced potting soil.
Remove your dwarf bottle brush tree from its container. Massage the root ball to break it apart. Unwind tangled roots and trim any broken roots. Then place the bottle brush in your container so it sits at the same depth as it did in the nursery container.
Fill the rest of the pot with soil, leaving a 1-inch lip at the top.
Water your bottle brush until the soil compresses around the base of the tree and liquid flows from the drainage holes at the bottom of the container.
Keep watering your bottle brush tree weekly, giving the tree 1 inch of water unless it receives sufficient rainfall that week.
Fertilise bottle brush trees each year in the spring. Use 10-10-10 fertiliser and apply the manufacturer's recommended dose size, based upon the tree trunk's diameter. Mix the right dose of water soluble fertiliser with water then water your tree with this solution to apply the fertiliser.
Prune your bottle brush tree annually to shape it and remove unhealthy wood. Trim dead or damaged branches plus those that compress other branches. Thin out the canopy by removing old branches or weak growth. Cut back the tips of long branches to lateral branches to shape the tree.
Bring your bottle brush tree in when temperatures fall near freezing. Some bottle brush varieties are more cold hardy than others but most receive frost damage at -7 to -10 degrees C.
Gardeners can attempt growing standard-sized Callitstemon linearis, Callistemon rigidus, Callistemon subulatus or Callistemon citrinus 'Splendens' outdoors. These are the most cold hardy trees. However, they should be grown against a wall and will only thrive in the most temperate parts of England.