Growing Bottlebrush Plants – Learn About Callistemon Bottlebrush Care
By: Jackie Carroll
Bottlebrush plants (Callistemon spp.) get their name from the spikes of flowers that bloom at the ends of the stems, bearing a strong resemblance to a bottle brush. Grow them as shrubs or small trees that grow up to 15 feet. Most bottlebrush varieties bloom over a long summer season in shades of red or crimson. One exception is C. sieberi, which has light yellow flower spikes.
Bottlebrush plants need a very mild climate. If you live in an area cooler than USDA plant hardiness zones 8b through 11, grow bottlebrush in pots that you can move to a protected area for winter. Use a rich, peaty potting soil with a few handfuls of sand added to improve the drainage. If pruned hard every year, the plants will grow in pots as small as 6 to 8 inches in diameter. If you plan to let the shrub grow, you’ll need a large tub.
How to Grow a Bottlebrush
Outdoors, plant bottlebrush shrubs in a sunny location. The plants aren’t picky about the soil type as long as it is well drained. If the soil is very poor, enrich with compost at planting time. Once established, bottlebrush plants tolerate drought and moderate salt spray.
Callistemon bottlebrush care consists of regular watering while the tree is young and annual fertilization until it matures. Water young trees weekly in the absence of rain, applying the water slowly to saturate the soil as deeply as possible. A layer of mulch over the root zone will slow the evaporation of water and help prevent weeds. Use a 2-inch (5 cm.) layer of shredded hardwood or bark or a 3- to 4-inch (8-10 cm.) layer of light mulch such as pine straw, hay or shredded leaves.
Fertilize bottlebrush shrubs for the first time in their second spring. A 2-inch (5 cm.) layer of compost over the root zone makes an excellent fertilizer for bottlebrush. Pull back the mulch before spreading the compost. If you prefer to use a chemical fertilizer, follow the instructions on the label.
Bottlebrush plant pruning is minimal. You can grow it as a shrub with several trunks, or prune it back to a single trunk to grow it as a small tree. If you grow it as a tree, the drooping lower branches may need cutting back to allow for pedestrian traffic and lawn maintenance. The plant produces suckers that should be removed as soon as possible.
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Bottlebrush Plant Profile
The Spruce / Evgeniya Vlasova
Bottlebrush plants (Callistemon) get their common name from their bristly and typically red flowers that look like a traditional bottle brush. The plants mostly flower in the spring and summer. They grow at a moderate rate and can be planted at any point during the growing season in their hardiness zones. They have an upright growth habit with fairly short, narrow leaves. Plus, they're popular desert perennials because they're colorful, inexpensive, low-maintenance, drought-resistant, and readily available.
|Common Name||Bottlebrush, Little John|
|Plant Type||Flowering perennial desert shrub|
|Mature Size||Up to 15 feet tall|
|Sun Exposure||Full sun|
|Soil Type||Loamy, moist, well-draining|
|Soil pH||5.6 to 7.5|
|Bloom Time||March to September|
|Flower Color||Red, white, yellow, green|
|Hardiness Zones||8 to 11|
Bottlebrush Tree Care & Growing Guide
1. Light Requirement
The bottle brush tree needs to be exposed to full sun for at least 6 hours a day to keep up its vibrant red flowers. Do not place this tree in the shade or by plants that are larger than it. If this plant is in a container indoors, it still needs to be exposed to a lot of direct light. Keep it near a very sunny window.
When this plant is young, it should be watered often. But when it reaches maturity it becomes more drought tolerant and it’s watering should become infrequent. Once a week is good in the spring and summer. Don’t water it if it has rained recently.
3. Climate and temperature
This plant doesn’t like extreme weather, so if you have hot or cold days, be sure to bring it inside if you can. It does best in hardiness zones 8 to 11. It can live in temperatures that range from 50F to 90F. If it is in warm weather, it can live in flower all year long.
This plant does well in any soil that is not too alkaline. It also does well in acidic soil. It will need to be fertilized in the spring and summer.
Spreading mulch around the soil underneath the bottle brush tree helps keep the soil moist and reduces watering even more. If this tree is in a container, it needs to be well-draining, or else it will quickly suffer root rot.
5. How to repot the Bottlebrush tree
Because this shrub grows so fast, it must be regularly repotted into bigger containers. In each repotting provide the bottlebrush with fresh soil. On average, it will be repoted every two to three years. If the roots of these plants are coming out of the drainage holes, then you know it’s time to change containers. Before you repot it, it must be trimmed back to encourage more growth. During repotting, shake out excess oil as much as you can around the roots. Slowly add fresh soil to its roots until they are entirely covered in the pot. When you are done, water the ground and make it damp.
6. Speed of Growth
The shrub is fast-growing, and they can grow up to 3 feet a year if the weather is right and there is fertilizer in the soil. Therefore, trimming the bottlebrush is so essential if you want to keep it at a certain height.
7. Height and Width of the plant
Even though this fast is a shrub and not a real tree, if the conditions are right, these plants can grow up to 15 feet tall. Constant trimming is needed to make sure it doesn’t grow farther than what you want. Its width can reach around 5 to 6 ft.
Trimming this shrub is a necessity as it helps promote growth and flower bloom. Trim the tips of the stems and clear any dead matter. Watch out not to snip off the flower buds.
Planting and Care
Bottlebrush plants can be grown from seed or from cuttings. The seed pods can be harvested from mature plants and dried at the end of the growing season to release seeds, then planted in a prepared seed bed (indoors or outdoors) in the spring. Bottlebrush is not picky about soil, but prefers moderate to light watering.
Cuttings gleaned from spring or fall pruning can either be placed in a container of water or planted directly in soil. Cuttings should be taken from semisoft wood. Remove leaves from the lower two-thirds of the cutting. The roots will form from a “wound response” — gently peel off bark from the lower third of cutting before sticking it in the soil. Water sufficiently to keep the soil moist, but not soggy. When propagating in water, change the water every other day to ensure freshness.
Watering and nutrients
If your bottlebrush is established outdoors and is growing well, you will probably not need to water it except during the driest months. Container plants will certainly need to be watered, but it is best to err on the side of too little moisture and to use a potting mix that drains easily. If you are growing your bottlebrush outside, you will want to use a fertilizer with an NPK of 10-10-10 that includes sulfur as a macro-ingredient. For indoor plants, a liquid fertilizer is best. Bottlebrush plants do not require a lot of nutrition in their soil, but they can react adversely to too much fertilizer. Use about half the amount recommended on the package and observe your plant for adverse changes. Yellowing leaves could indicate a need to reduce the amount of fertilizer.
The ends of the bottlebrush blossom are dusted with pollen, which attracts a variety of pollinator insects and birds. These hardy plants are often self-pollinating. However, if you have more than one type of bottlebrush growing in your garden, insects and birds can help them cross pollinate.
Your growing situation will dictate how much pruning your bottle brush will need. In excellent conditions, a bottle brush tree can grow up to 30 feet tall. This will create a lovely architecture tree for your backyard or other outdoor area. Not everyone has that kind of space, however. Regular pruning will help keep your bottlebrush at an ideal height and shape for your garden. For shape, prune it in the spring before it begins to put out flower buds. In late summer or early autumn, or anytime you see a problem, your bottlebrush can be pruned for health or size.
Pests and diseases
Even though bottlebrushes are generally an easy plant to care for, they are susceptible to a variety of pests and diseases.
- Root rot. This is a common problem for novice gardeners who worry about remembering to water. However, your bottlebrush plant will love a little neglect in this regard. Once root rot has set in, it is almost impossible to combat. Fortunately, it is easy to avoid and the solution is to plant your bottlebrush where it will have good drainage and to water lightly.
- Powdery mildew. This is a condition that loves excess moisture and goes hand in hand with overwatering. The solution is to treat the plant with a fungicide. Pretreat plants with a PM spray to avoid the spreading of PM spores. Cleaning up fallen leaves will also reduce infection.
- Twig gall. Overwatering encourages this condition as well. The solution is to cut away infected parts, reduce watering, and make sure your plant is getting plenty of sunlight.
- Verticillium wilt. Also a result of overwatering, verticillium wilt is difficult to diagnose because it resembles several other conditions. If you suspect verticillium wilt is affecting your plant, cut off a twig. An infected plant will have dark rings of color in the cross-section. Removing the affected branches will help the plant build resistance. If the plant cannot be saved, be sure to dispose of it away from other plants, and do not replant susceptible species in that same location.
As a native of Australia, this plant likes to be kept warm. In mild climates, it can live all year round, though if you live in an environment where winters are cold, then you will need to grow the bottlebrush tree in a container so that it can be moved inside during chilly months.
The bottlebrush tree thrives in full sun and needs plenty of direct sunlight to produce the striking brush-like flowers. If you are planting this tree directly into the ground in your garden, ensure it is in an area that will get at least six hours of sun a day. Watch out for neighboring plants which might grow bigger than the bottlebrush tree, resulting in it being put in the shade by the bigger plant.
For encroaching plants, cut them back to enable the bottlebrush tree to have full access to daylight, or dig up your bottlebrush tree and replant it in a more suitable location. Bottlebrush trees in containers will need to be positioned in a sunny spot and can be moved around if necessary to give them the best chance of good health and flower production.
If you want to propagate your bottlebrush tree, you can do so from seeds or from stem cuttings (Royal Horticultural Society). Both options are easy and very rewarding to do.
To collect seeds from your bottlebrush, you will need to locate the woody fruit produced by each blossom on the plant. You will be able to find these small fruits growing along the flower stems in clusters. Remove them from your plant, unopened, and store them in a cool, dry place inside a paper bag. Then, wait for the fruits to open, revealing hundreds of tiny seeds from each fruit. Sow the seeds during spring in moist soil and wait for seedlings to appear, transferring them to slightly larger pots when mature enough and continuing care as usual for young shrubs.
Due to the common cross-pollination of bottlebrush trees, growing the plant from seed does not guarantee that the new plant will be the same variety as the mother plant. If you are keen to ensure your new plants are a direct copy of the parent plant, you will need to propagate using stem cuttings instead of seeds.
Propagation by stem cuttings can be done during summer with semi-mature woody stems. Make your cut with clean shears at a 45-degree angle to create the most surface area from which roots can form. Your cutting will need to be around six inches in length, with all of the lower leaves removed. Any flowers or flower buds will also need to be snipped from the cutting. You can dip the raw end of the cutting in rooting hormone to encourage roots to form and increase your chances of successful propagation, but it isn’t entirely essential and can be skipped if you wish.
Stand the cutting in either a jar half filled with water or in a small pot filled with soil, ensuring that the soil is packed tightly enough around the stem to prevent it from falling over. If you are using soil to propagate your stem, keep it moist but not wet, and, ideally, cover it with a plastic bag to help increase humidity.
If you are using water to propagate your stem, change it at least every other day to keep it fresh. Place the stem cuttings in a warm place, ideally with bottom heat, and no direct sunlight. In eight to twelve weeks, your stems should have rooted. If you are propagating in water, then the development of stems is easy to witness.
If the stems are in the soil, you can check to see if roots have formed by gently tugging on the stem and seeing if it offers any resistance. Stems which will easily be pulled from the soil do not have any roots, while those that hold onto the soil are showing evidence of root development. Once roots are present, you can remove the plastic covering and move the pot outside to a warm and sunny spot. Ensure the young plant is well-protected from strong winds and continue care as normal, either planting directly into the ground or into a bigger pot when the plant is strong enough.
What Are the Best Tips for Bottlebrush Pruning?
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There are several reasons for bottlebrush pruning. Prune to improve the shape, allow clearance, and create the type of landscape that works best in the garden. Bottlebrush plants have a tendency to send up suckers, so it is necessary to trim those back at regular intervals. The bottlebrush is also propagated from cuttings, so careful pruning is necessary to create starts for new bottlebrush plants.
For major shaping and propagation, prune the bottlebrush in early spring, and remove suckers as they appear, throughout the year. It is important to remember that aggressive pruning in the fall may trigger a growth spurt. An early frost can then kill the young growth, leaving the bottlebrush with an uneven shape, and susceptible to further damage.
When removing suckers, use a sharp pair of pruning shears and clip the sucker off even with the ground. Left alone, the suckers will continue to grow, giving your bottlebrush a messy silhouette. Check the plant regularly for suckers, as they are much easier to remove when small.
To perform bottlebrush pruning for shape, step away from the plant and decide which limbs need to go, in order to improve the overall shape of the plant. Bottlebrush pruning is not an exact science, the shape that works best in each garden depends on other landscaping, and the needs of the homeowner. Some people grow one bottlebrush as a specimen plant, with s single trunk that grows into an arching canopy of color. Others prefer to use bottlebrush plants as privacy screens, and prune the tops down so that the plant develops multiple trunks and dense, low growing foliage. Regardless of how aggressively the bottlebrush is pruned, make each cut where a leaf joins the stem.
The heavy flowers of the bottlebrush may pull some of the limbs down over time, creating another reason for bottlebrush pruning. If the plant is located alongside a driveway or sidewalk, prune that side first. After determining how much clearance is needed, work around the tree to create a symmetrical look.
In order to take a cutting from the branches of the bottlebrush, cut a sucker or branch from the plant using a sharp pair of pruners. This creates a clean cut that is less likely to let bacteria or fungus into the growing plant. Dip the cut end of the bottlebrush in rooting hormone, then plant in moist soil.
Proper bottlebrush pruning allows the bottlebrush to grow strong and healthy. This shrub is an excellent choice for landscaping it grows in a variety of conditions and is resistant to many diseases and pests. The bottlebrush is an evergreen, and has a canopy of spiky flowers that attract hummingbirds while in bloom.
Q. Our bottle brush shrub appears to have winter kill
Our bottle brush shrub appears to have winter kill, as the leaves have turned brown. It has always produced blooms and is a relatively small upright shrub. Do I prune heavily or lightly to see if it responds? This shrub faces east and is located in the foundation plantings. All the leaves have turned brown, which I have never before seen on this shrub. It is about 6 feet tall, but not heavily branched. It also experienced an ice storm we had the previous winter (which is very rare here in southern NC) however, the shrub rebounded. We did have an exceptionally cold winter here this year. Should I be wrapping this shrub in burlap each winter? This shrub is about 6-7 years old but has grown slowly.
Yes, we did have an incredibly cold winter, and it would sound as if your Bottlebrush has suffered winter damage. I would recommend pruning the damaged and dead leaves and branches, and wait and see. Give the roots time to wake up and then you can access the plant.
Burlap wrap is a good way to protect shrubs and plantings in the winter.
I have listed a few links for you with more information.