Callistemon

( kal - liss - STEEM - on )

at-a-glance information

Callistemon, commonly known as Bottlebrush, is a genus filled with species of trees and shrubs native to Australia. They prefer full sun and moderate to regular water, though these preferences depend on the species grown. Some forms are dense and compact, others are sparse and open; all are evergreen. Use Callistemon plants as hedges, specimen trees, grown in containers on patios or walkways, along fence lines, or as parts of mixed beds and borders. The flowers will attract pollinators to the garden.

Callistemon species and varietals

The genus Callistemon is a member of the plant family Myrtaceae and includes around 50 distinct species. The genus name is derived from the Greek words for beauty (callis) and stamen (stemon), referring to the plant's unique flowers. Many species once in this genus have been moved into Melaleuca, a closely related genus of trees and shrubs. The best growing zones for Bottlebrush plants vary depending on the species. To find your zone, click here: Zone Map.

Callistemon citrinus (Melaleuca citrina) (Lemon Bottlebrush)
This species is best in USDA hardiness zones 8-11 or Sunset growing zones 8, 9, 12-24, H1, and H2, taking temperatures down to 15 to 20 degrees Fahrenheit. This is the most commonly cultivated species of Bottlebrush. Individual plants can grow to reach 10 to 15 feet tall and wide as a shrub, but when pruned into a tree, can reach 25 feet tall. Leaves are copper when young and mature to green. This species gets its common name from the lemon smell the leaves have when crushed. Varietals include 'Violaceus', 'Mauve Mist', and 'Perth Pink' (pictured).

Callistemon rigidus (Melaleuca linearis) (Stiff Bottlebrush, Erect Bottlebrush, Narrow-Leaved Bottlebrush)
Grows best in USDA hardiness zones 9 and 10 or Sunset growing zones 8, 9, 12-24, H1, and H2. It is grown as a sparse shrub or a small tree with a height of 20 feet and a width of 10 feet. The points of the leaves are sharp, and colored grey-green. In spring and summer, red brushes are produced. This variety produces many seed capsules, and is the least graceful of the bottlebrush varieties.

Callistemon salignus (Melaleuca salicina) (White Bottlebrush)
This species does well in USDA hardiness zones 8-11 or Sunset growing zones 8, 9, and 12-24. It can be grown as a shrub or tree, and reaches 20-25 feet tall and 10-15 feet wide. New growth is pink and turns copper and over time. Mature leaves are green and linear. Pale yellow to cream-colored flowers appear in clusters in spring and early summer. Plants in this species can be trained to form small shade trees. If creating a hedge, plant 4-5 feet apart for best coverage and airflow.

Callistemon sieberi (Melaleuca paludicola) (Alpine Bottlebrush, River Bottlebrush)
This species grows well in USDA hardiness zones 7-11 or Sunset growing zones 5-9 and 14-24. It forms a shrub that grows up to 3-6 feet tall and wide with an upright habit. Leaves are dense and dark green. Flowers are yellow or cream colored and appear in clusters in late spring to midsummer. This is a good Bottlebrush to choose for cooler climates.

Callistemon viminalis (Melaleuca viminalis) (Weeping Bottlebrush, Creek Bottlebrush, Drooping Bottlebrush)
This shrub or small tree grows to 20-30 feet tall and 15 feet wide. This species does well in USDA hardiness zones 9-11 or Sunset growing zones 6-9 and 12-24. Leaves are light green and narrow. Red flowers appear in late spring and summer. Not suitable for windy, dry areas, and needs to be staked. Varietals include the dwarf 'Little John', 'Captain Cook', 'Red Cascade' (pictured), and 'McCaskillii'.

Callistemon viridiflorus (Melaleuca virens) (Green Bottlebrush, Mountain Bottlebrush, Tasmanian Bottlebrush, Lemon Bottlebrush)
Grows in USDA hardiness zones 7-10 or Sunset growing zones 4-9 and 14-24. Open, upright habit, grows to 6-8 feet tall and wide. Bark is golden and flaky. Leaves are dark green and dense. Flowers are green to creamy yellow and appear from spring to summer.

Caring for Callistemon

Callistemon, or Bottlebrush, plants are typically purchased as specimens from a reputable nursery, though they can also be grown from seed. These plants should be installed in a space that receives full sun; ideally, between 6 and 8 hours each day. Ensure that soil is well-draining, rich in nutrients, and has a pH of between 6.0 and 7.5 (slightly acidic to neutral). If local soils are particularly poor in nutrients or do not drain well, make sure to amend the planting area with plenty of organic compost before installing. Apply a layer of mulch around the planting area to suppress weed growth, maintain consistent soil temperatures, and to increase soil moisture retention. Once established, Bottlebrush plants only need occasional water and are considered drought-tolerant. Make sure there is no standing water at the roots.

Fertilize yearly in early springtime with an application of 2 inches of compost around the base of plants. Pull mulch back before applying, work the compost gently into the soil a bit, water it in, and then replace mulch. Pruning is key for Bottlebrush trees and shrubs, as it dictates how well they will flower. Pruning for the health of the plant should be done in spring or late summer. Remove interior branches that are damaged or diseased, and the plant can be thinned slightly if inner growth is turning brown due to lack of sunlight. Lightly thin branches so that more sunlight can reach the interior of the plant. Also, feel free to remove any suckers and forking or crossing branches. Prune again for shape when the flowers fade. Keep all pruning minimal and try to make cuts only a few inches below the tips of each branch. Bottlebrush look best when allowed to keep their natural shape, but can be pruned into a tree form with an umbrella-like top. Callistemon plants typically live for between 20 and 40 years in the landscape before needing to be replaced.

Caring for Callistemon in Containers
Callistemon, or Bottlebrush, shrubs and trees are wonderful in the ground, but can also be grown in containers. Choose a container that is at least a few inches wider and deeper than the nursery pot or root ball. Ensure that the pot has adequate drainage holes on the bottom to allow for excess water to flow away. Fill with a well-draining potting mix amended with organic material and perlite, and top with a layer of mulch to suppress weed growth, maintain consistent soil temperatures, and to increase soil moisture retention. Water regularly as the plant establishes itself in its new home. Once established, waterings can be lessened. Callistemon plants grown in containers will need more frequent irrigation than those grown in the ground. As a general rule of thumb, water whenever the top few inches of soil feels dry to the touch. Prune to remove dead, damaged, or diseased foliage at any time during the growing season. Every few years, check the bottom of the pot to ensure that the plant is not outgrowing its root space. If roots are growing through the drainage holes in the bottom of the container, it is a good indication that it needs to be potted up; choose a slightly larger container and repot.

propagation

Callistemon, or Bottlebrush, can be propagated either by using cuttings or from seed. To ensure that your propagated plant will have the exact same qualities and characteristics as the parent plant, use the cutting method. If you would like to experiment and see what plant you can grow from seed, just keep in mind that it will not necessarily be the same as the parent plant. To propagate your Bottlebrush shrub or tree, follow the instructions below:

Propagating Callistemon by Cutting

Gather your materials. You'll need a clean, sanitized, sharp pair of garden shears, rooting hormone, a pencil, and a 3-inch pot filled with well-draining compost or other organic material. A good substrate for propagation of cuttings is a light blend of 1/3 pasteurized soil or compost, 1/3 sand, vermiculite or perlite, and 1/3 coconut coir or peat moss.
In spring or early summertime, choose the plant that you'd like to propagate. Ensure that this plant has had a good watering the night before, as this will improve the chances your cutting will take root. Cut one or more 6 inch semi-hardwood portion(s) of the end of a non-blooming branch and strip the leaves off of the lower half. Make a hole in your planting medium by pushing your pencil into the soil. Dip the end of the stem in rooting hormone, and plant it in your pot. Fill in soil around the cutting to support it, but do not pack it down too much.
Moisten with water, and ensure that the pot has good drainage. Your pot should be kept in warm, sunny conditions indoors (and not in direct sunlight). Water whenever your soil is dry under the top layer. After about four to six weeks have passed, your cutting should be rooted. When you notice new growth, you'll know you have roots.
Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring, when you can transplant it to its new home. Ensure that the last frost of the year has occurred before doing this, as it can seriously damage your new shrub.

Propagating Callistemon by Seed

Keep in mind that the plant you get from seed will not necessarily mimic all of the characteristics of the parent plant. To propagate by seed, you will need a paper bag, a pot or tray filled with well-draining compost or other organic material, a spray bottle and a fork. The best potting medium for seed germination is a light blend of 1/3 pasteurized soil or compost, 1/3 sand, vermiculite or perlite, and 1/3 coconut coir or peat moss.
Harvest your seeds. Once the seed pods have dried out and begun to split open, you can harvest the seeds inside. Cut them off of the plant, placing them in a paper bag. Harvest as many as you can, and place the paper bag in a dry, cool, dark area. They will begin to split open and release the seeds contained inside. Once they have been released, take them out of the bag and put them in a container so you can work with them.
Water your prepared seed tray or pot filled with soil, and ensure that good drainage is occurring. Place your seeds in your prepared pot or seed tray about a quarter inch to a half-inch under the soil surface. Cover them with soil and water with your spray bottle. Place your tray of seeds in a warm area that receives bright, indirect light. A greenhouse is the most ideal climate, but a planting tray inside a window will do as well. Germination usually takes 7-14 days from sowing. Once you begin to see seedlings sprout and they are able to be handled, transplant them to their own individual 3-inch pots, filled with the same potting medium as described in Step 1. Loosen the seedlings from the potting medium by digging down with the tines of your fork about an inch and a half, gently working the seedling up until it is out. Then, replant the seedling in its individual pot.
Keep the seedling's potting medium moist, but not wet, by spraying the soil with your spray bottle. Keep your new plant in an area with bright light (though not direct sunlight) and temperatures between 55 and 70 degrees Fahrenheit. Ensure that the soil stays moist, but not wet, until the next spring (after the danger of frost has passed), when you can transplant it to its new home.