The Callistemon spp. or commonly known as Bottlebrush, are well-known for their vibrant and bushy flowers that bloom all-year-round. They are also a favorite of hummingbirds! With a wide variety of species and cultivars available, from small shrubs to towering trees, you can easily find the perfect bottlebrush plant to suit your preferences.
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What You’ll Learn
– Background and Evolution
– Propagation
– Growth Strategies
– Tips for Growing
– Maintenance and Pruning
– Choosing Between Species and Cultivars
– Managing Pests and Diseases
– Best Applications
– Quick Reference Guide to Growing
Background and Evolution
Bottlebrush represents the scientific name for Callistemon, which denotes a variety of flowering evergreen shrubs found in the Myrtaceae family.
It’s important to note that the bottlebrush plant mentioned here is not the same as Sanguisorba obtusa or Aesculus parviflora, which are also referred to as bottlebrush plants. These shrubs are originally from Australia but can be found growing in many other countries. The C. citrinus species was brought to Europe by botanist Joseph Banks in the late 1700s and quickly became a beloved addition to gardens.
You can cultivate these bushes all year outdoors in areas that belong to USDA Hardiness Zones 8b to 11b. In regions with colder weather, it’s best to bring them inside during winter. These plants are famous for their lively clusters of red, white, yellow, or crimson blossoms that look like bottle brushes. The leaves are sharp, petite, and slender and come in various shades of blue-green, green, or silvery.
The period of blossoming lasts for a significant amount of time, with flowers appearing all through the summer and enticing various pollinators such as butterflies, bees, hummingbirds, and wasps. These shrubs can grow anywhere from three to 15 feet tall and some species have the potential to be shaped and trained into towering trees that can reach a maximum height of 25 feet.
Bottlebrush plants are closely related to paperbarks, which share similar flowers from the Melaleuca species. However, there is ongoing discussion among botanists as to whether Callistemon and Melaleuca should be classified separately or as one genus. This debate led to the merging of most Callistemon species with Melaleuca in the early 2000s, but not all botanists agree with this decision. Despite the controversy, bottlebrushes are still commonly labeled as “callistemon” in commercial nurseries.
If you’re interested in propagating bottlebrush plants, there are two methods you can try. The first involves collecting the small woody fruits that remain attached to the plant for up to three years and extracting the seeds. This can be done at any time of year. The second method is rooting stem cuttings. While both techniques require some effort, they can be rewarding for those willing to put in the time.
If you’re searching for unopened fruits, check out the lower part of the tree branches. It’s recommended to pick the ones that are at least a year old to get the desired outcome.
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Firstly, put the fruit in a paper bag and leave it in a warm and dry place. Wait for a few days until the fruit splits and reveals small seeds inside. It’s best to use fresh seeds. Then, sow each seed on the surface of moist and well-drained potting soil in a four-inch pot. To keep the moisture, cover the pot with a plastic dome and place it in a warm area that receives bright but indirect light. You can use a heat mat to keep the temperature around 80°F consistently. Make sure to keep the soil damp until the seeds start to germinate, which should take around two weeks. Once the seedlings start to grow, remove the plastic dome but still keep the soil moist and in a well-lit area. Once the seedlings reach three inches tall, you can transfer them to bigger pots that are two gallons in size.
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To nurture your plants, make sure you keep them in a warm and well-lit area indoors for six to nine months. If you reside in an area that experiences light frost during winters, it is better to wait until the frost risk has passed in spring before transplanting them outside. Another method you can use is growing a bottlebrush from cuttings which requires some patience and attention. During summers, take a stem of about six inches from a healthy bottlebrush plant having three or more pairs of leaves. Trim all other leaves except the pair at the tip along with any buds, and you’re good to go!
To propagate bottlebrush shrubs, find a container that is at least six to eight inches in diameter and five inches deep. Fill it with a soilless mixture of half peat moss and half perlite. Dip the cut end of the stem in rooting hormone powder and plant it three inches deep in the pot. You can plant multiple cuttings in the same pot if desired. Keep the planting medium moist and cover the container with a clear plastic bag to retain moisture. Place the container in a warm spot with filtered light for at least six to eight hours a day. Remove the plastic bag for a few minutes daily to allow air circulation. In four to six weeks, check for root formation by gently tugging on the stem. If there is resistance, it means roots have formed and the cutting is ready for repotting in a peat-based potting soil mix. Wait until all risk of frost has passed to plant outdoors. To harden off seedlings prior to planting, set them outside gradually for a few hours each day, increasing the time and direct sunlight exposure as planting time approaches. When planting, dig a hole slightly larger than the root ball and backfill with garden soil and compost. Mulch the base of the plant with a few inches of shredded bark or pine needles and water well. For optimal growth, place the shrubs in full sun, but they will tolerate part shade. Space them three feet apart when planting multiple shrubs in one area.
Loamy soil is the ideal choice for planting, but don’t worry if you don’t have it; these plants are not very selective about soil types. Just make sure to enrich the soil with compost during planting. Additionally, it’s crucial to select a spot with well-draining soil. To improve drainage, mix compost into the soil and use mulch.
During the first few weeks after planting, make sure to water the shrubs every week by thoroughly saturating the soil. Once they become established, most species can withstand drought conditions. Unless the soil is extremely dry due to prolonged drought, watering should only be necessary during such periods. Avoid standing water as it can cause rotting.
It’s not necessary to use chemical fertilizers, and an excess of nitrogen could adversely affect flowering.
Instead of leaving the mulch as is, it’s recommended to remove it every spring and apply a fresh layer of compost about two inches deep, covering the soil all the way to the end of the drip line. These shrubs that thrive in arid regions can bear high temperatures, but on the other hand, they’re intolerant to frost. In case of any predicted freezing temperature, it’s advisable to safeguard the shrubs by wrapping them up in a sheet or muslin cloth, ensuring there’s an opening at the top for ventilation to avoid powdery mildew and leaf spot. If you notice some browning on the leaves, no need to fret as they should recover as long as the branches remain intact.
Although you can keep heat-loving plants safe during temporary cold spells, they won’t last long in freezing temperatures. If you live in colder areas, it’s best to cultivate these shrubs in containers or transfer them to pots to bring inside during the winter. Ensure that you choose a large pot that’s at least 16 inches in diameter with adequate drainage and fill it with peat-based potting soil mixed with sand to enhance drainage. Keep the pot in a bright indoor space, check regularly, and water occasionally when the soil is dry; fertilizing isn’t necessary during the winter. Wait until after the last frost before bringing the potted plants back outside to harden off for a week or two before returning them to their sunny spot.
If you’re planting bottlebrush, make sure that they receive at least six to eight hours of sun daily and amend the soil with compost before planting. Water deeply once a week until the plant is well-established, then only during prolonged dry spells. Protect from cold spells by covering the plant with a sheet or muslin cloth, and move indoors during winter if you live in Zones 8a or below. Bottlebrush can either be grown as a shrub or pruned into a single trunk resembling a tree.
During the end of winter, it is possible to trim the lower branches that are drooping to achieve the desired shape. To do so, it’s important to cut each stem individually just above a node on each branch. While pruning, ensure that any suckers growing from the roots are cut back to the ground level. For general maintenance, pruning should be done either in early spring or late summer. During this time, it’s essential to remove any dead or damaged branches and any branches showing signs of disease. Additionally, lightly thinning the interior branches can improve sunlight exposure and airflow. For those growing bottlebrushes in pots, heavy pruning each year is necessary to keep the shrubs to a manageable size. There are numerous species available in a range of colors and sizes, varying from dwarf shrubs to trees. Crimson or scarlet bottlebrush (C. citrinus) is a popular species featuring showy, vibrant red flowers with contrasting tips.
The Crimson Bottlebrush is a stunning plant that looks even more beautiful in the setting sun. The lemony fragrance emitted by its foliage on hot days adds to its charm. With maturity, these shrubs can grow up to 10-15 feet tall. If you’re interested in purchasing this plant, you can find it in #1 containers at Nature Hills Nursery. The Weeping variety of the bottlebrush, also known as C. viminalis, is another gorgeous option. It grows much taller than the Crimson Bottlebrush, reaching 15-20 feet in height. Its blue-green foliage and dense spikes of deep red flowers that can grow up to six inches in length make it a showstopper. You can enjoy its blooms from spring through early summer and intermittently into the fall.
The ‘Little John’ plant, scientifically known as C. viminalis, is a small and slow-growing shrub that only reaches a height and width of three feet. Its branches are dense and adorned with blue-green leaves that smell like citrus when crushed. The plant blooms with striking blood-red flower spikes that last for a long time.
The plant variety called ‘Little John’ is perfect for those who prefer container gardening. You can easily purchase these plants online or from stores such as Home Depot and Fast Growing Trees, in three-gallon pots. C. salignus, also known as willow or white bottlebrush, exhibits lush foliage resembling that of a willow tree. It produces pink or red leaves when young and sports yellow or creamy white flowers.
This plant, which can reach a height of 25 feet and is always green, requires low maintenance. However, it is still important to watch out for pests and diseases. There are insects that can cause damage to the foliage and transmit diseases if not addressed. One such pest is the root-knot nematode, a tiny roundworm that feeds on roots. It can sometimes invade bottlebrush trees, leading to a slow decline in their overall health. To identify its presence, look for swollen roots, wilting, and yellowing leaves. The plants will appear dry even when the soil is moist enough. Unfortunately, there isn’t much that can be done to eliminate these nematodes once they appear. But using thick mulch, such as shredded bark or pine needles, around the plants can help suppress the population. Leaving a couple of inches bare around the stem will prevent it from rotting. Proper watering, pruning, and providing good growing conditions can reduce the risk of this pest. Another menace is sawflies, whose larvae congregates to feast on the leaves, decimating the foliage of an entire shrub in no time.
To eliminate larvae, manually remove them or use neem oil for larger infestations. Scale insects are known to gather and feed on sap in groups, producing a sticky substance that can attract ants and lead to sooty mold. Applying horticultural oil such as neem oil or insecticidal soap can help eliminate scale. Excessive moisture can cause problems for bottlebrush shrubs, resulting in powdery mildew, root rot, sooty mold, twig gall, and verticillium wilt. Powdery mildew appears as a white coating on foliage, and organic methods like applying milk or baking soda can help control it. Root rot can be avoided by planting in well-draining soil and avoiding overwatering. Sooty mold is a fungal disease caused by a scale infestation, while twig gall is caused by a fungal disease called Sphaeropsis tumefaciens. Verticillium wilt is a soilborne fungal disease that is difficult to eradicate once present. Bottlebrush shrubs are aesthetically pleasing and attract pollinators when in bloom.
The lush leaves of these plants make them perfect for creating dense hedges, and their vibrant hues add an extra touch of beauty. You can also use them to border your driveway or walkway, or plant them as lovely foundation plants beneath a window.
A great way to add some pizzazz to your deck or patio is by featuring container plants as the centerpiece. This not only adds some color and visual interest to the space, but it also allows for easy rearranging if you want to switch things up.
Bottlebrushes have the additional advantage of being used as cut flowers to beautify your home. The leaves produce a citrusy fragrance when squeezed, so you can add a delightful aroma to your space by pinching them while incorporating them into floral arrangements. This evergreen flowering shrub is native to Australia and comes in various colors such as red, white, yellow/blue-green, green, and silver. It requires minimal care and maintenance and can endure heat and drought conditions. Its blooming season is during the spring and summer months, and it prefers full sun exposure with well-draining loamy soil having a pH range of 5.6-7.5. Proper spacing of 3 feet is recommended, and the plant’s height can reach up to 25 feet with a spread of 15 feet. Bottlebrushes are a great addition to borders, foundation plants, and focal points and can attract hummingbirds, butterflies, bees, and wasps. They take approximately two years to mature and belong to the Myrtaceae family under the Callistemon genus. Furthermore, they have low water requirements but are vulnerable to root-knot nematodes, sawflies, and scales infections and diseases like powdery mildew, root rot, sooty mold, twig gall, and verticillium wilt.