Cotoneaster is a species that is ideally suited to bonsai. They are hardy, have a beautiful growth habit and are very widely available. Keep reading this guide to find out all you need to know about Cotoneaster bonsai tree care.
If you are a beginner, then Cotoneaster is one of the best species for bonsai that you could start your collection with. They are very forgiving and look lovely.
- What do Cotoneaster trees look like?
- Where to grow Cotoneaster bonsai
- Watering Cotoneaster bonsai
- Pruning Cotoneaster bonsai trees
- Wiring branches
- Cotoneaster bonsai styles
- How do you fertilize Cotoneaster?
- How do you propagate Cotoneaster?
- Cotoneaster bonsai FAQs
What do cotoneaster trees look like?
Cotoneasters are small plants that grow as trees, shrubs or as ground cover. They generally grow between 0.5m-5m tall and can often be found in alpine regions. Cotoneasters are native to Asia, Europe and North Africa and there are around 300 known varieties.
When it comes to bonsai, Cotoneaster horizontalis is very popular as well as Cotoneaster microphyllus.
Despite there being so many types of Cotoneaster they do generally share the same characteristics. They have small ovate leaves that are usually a deep green color in spring and summer and can turn to orange or red during autumn.
Cotoneaster bonsai can be both deciduous and evergreen, depending on the variety and the climate. If you are based in a warmer climate your Cotoneaster will be more likely to be evergreen, while bonsai grown in areas with cold winters will be more likely to go fully dormant and drop their leaves.
Cotoneasters are well known for the 'herringbone' growth habit of their branches, which occurs with alternating short branches coming from a thicker structural branch.
In late spring/early summer Cotoneasters will produce small white or pink flowers. These will eventually grow into small red berries that can stay on the tree year-round in some varieties.
The small growth habit of Cotoneaster along with its flowering and fruiting capabilities make it a great species for bonsai.
Where to grow Cotoneaster bonsai
In nature, Cotoneasters are generally found in colder temperate climates. Because of this, Cotoneasters are not suitable to keep as indoor bonsai and must be cultivated outside.
Most species of Cotoneaster prefer to be grown in full sun or dappled shade through the growing season. If you live somewhere with very hot summers it would be a good idea to keep them in semi-shade through the height of summer.
Cotoneasters are hardy plants that can tolerate cold winters. They can be kept outside through winter and should be protected as appropriate based on the size of the pot, the age of the bonsai and health of the tree. If the pot is small, the bonsai is old or if the tree is unhealthy, then be more cautious with your winter protection. Winter protection options from most to least cautious include:
- Putting the tree in a greenhouse
- Placing the tree in a wind shelter
- Heeling in the tree with leaves or mulch
- Moving the tree off the bench and onto the ground
Watering Cotoneaster bonsai
There are no specific pitfalls with watering for Cotoneasters. They are tolerant of all water types and can bounce back quite well from the odd missed watering (but we wouldn't recommend you test that!).
As with all bonsai trees, you should avoid overwatering by only watering when the top level of soil has dried out. When you apply water, make sure you thoroughly drench the whole root ball.
It is also advisable to water only the soil (where possible) and avoid the foliage. This is because water is a good vector for spreading fungal diseases that could infect your Cotoneaster's foliage.
If you're unsure how to water a bonsai tree properly, check out our bonsai watering checklist.
Pruning Cotoneaster bonsai trees
Compared to many other species used in bonsai, Cotoneasters are relatively simple to handle. They respond well to regular pruning and will grow very nice ramification and internal branching as a result.
Cotoneasters should be trimmed regularly through the growing season by cutting new growth back to two buds or leaves. These will then grow further and you repeat the process, resulting in lots of fine branching.
To prevent the tree from losing energy and resources you should allow the leaves to harden off before pruning. The indicators for this are the development of a waxy coat on the exterior of the leaf, as well as a deepening of the shade of green. Once a leaf has hardened off you can be sure it has 'paid back' the energy used to grow it, so you can prune without weakening the tree.
A Cotoneaster bonsai ready for its first pruning of the year. Note the elongating shoots.
As with pruning, wiring can happen throughout the growing season. However, you may find it easiest to wire in autumn after leaves have dropped or in spring before growth has started because leaves won't be blocking your path for wire application.
I would avoid wiring your Cotoneaster bonsai in winter because the tree will not be active enough to repair any damage caused by the wiring process, which could lead to lost branches.
Cotoneasters are generally quite flexible and can be manipulated into shape easily. Older branches can sometimes be more brittle and prone to snapping, but you should be able to achieve your design through a combination of branch wiring and guy wiring.
You can use either copper or aluminium wire with Cotoneasters. Copper can hold bends more strongly as it hardens as you bend it, and also has the advantage of requiring a smaller diameter of wiring to achieve the same result that aluminium would. Aluminium is a softer wire which is ideal for very thin-barked trees. Some practitioners prefer to use it for most of their bonsai because it can be easier to apply.
Cotoneasters have a relatively rough trunk that can heal minor wire scars, but I would avoid letting wire bite in too much and remove wire when you see it getting tight.
Cotoneaster bonsai styles
Since Cotoneasters naturally grow as ground cover, they are well suited to smaller sized bonsai, such as Shohin, Kifu or Chuhin. Their creeping nature also facilitates cascade or semi-cascade styles with little difficulty. This is a particularly good style if you are working with young nursery stock. Cotoneasters are versatile and can also be styled into nice informal upright trees.
The tree I've featured in this post is a yamadori Cotoneaster originally collected by my grandfather. It suffered some health issues and lost the leading trunk but over the last couple years it has regained its health after some TLC and now has some really interesting deadwood.
How do you fertilize cotoneaster?
As with all bonsai, the first thing you need to consider when fertilizing your Cotoneaster bonsai is what are you trying to achieve?
Trees do not need fertilizer to survive. It is a supplement that will drive growth, thickening and vigour in your tree. Based on this knowledge, you need to decide how to use fertilizer to improve your bonsai:
- If you want to grow more roots, increase branch and trunk thickness or heal wounds, then you should fertilize aggressively.
- If you want growth in some areas without making the tree go wild, you should fertilize moderately.
- If you want to maintain the tree's current shape and maintain its health, you should fertilise lightly or not at all.
You also need to consider two other questions - organic or chemical, and liquid or solid.
For bonsai, I would always recommend organic fertilizer. Trees growing in the confined environment such as bonsai pots create rely on a relationship between healthy microscopic organisms in the soil and their roots (mycorrhiza). Organic fertilizers promote the development of this relationship. Chemical fertilizers can help with tree growth over the short term, but they can be detrimental to the soil system of your tree over the long term, which can increase your bonsai's susceptibility to disease.
When it comes to liquid or solid either will work well for your Cotoneaster. I opt for solid simply because it is more practical. You can apply it once and not think about it for weeks, whereas with liquid fertilizer you need to remember to apply it more frequently.
Solid fertilizers do require an established population of healthy bacteria to break it down for your tree to use, so in some cases, I use a combination of solid and liquid.
Cotoneasters will need to be repotted every few years. You should consider repotting your bonsai if it has filled the pot with roots so water can't percolate through, or if the soil has started to decompose and become sour.
Cotoneasters generally need repotting every 2-4 years, but you should avoid repotting on a schedule and instead rely on the above characteristics.
Repotting should be performed in late winter or early spring before growth has started. In my garden Cotoneasters are the first trees to be repotted because they are the first to start growing each year.
When repotting your Cotoneaster bonsai, make sure you reduce the topsoil to reveal the nebari (root flare), remove matted roots on the bottom and sides of the root ball, and remove decomposing or soured soil. Decomposing soil will be black, wet and sometimes a bit sweet-smelling.
The bottom matt of roots on a Cotoneaster bonsai 2 years after its last repot. These roots do not function well and the health of the tree is definitely improved by removing them.
You should use a well-draining soil mix. I use akadama for my trees, but if you can't source that a bonsai store will be able to sell you pre-mixed soil suitable for deciduous trees.
When choosing a pot, consider the features of the tree you want to highlight. Blue is a great color for Cotoneaster bonsai trees because it contrasts the red of their berries.
How do you propagate Cotoneaster?
Cotoneasters are very easily propagated through a variety of methods.
The most common method is via soft-wood cuttings. These are best taken in early summer. Dip your cuttings in rooting hormone then place them in a well-draining medium such as perlite or akadama. Mist foliage regularly to prevent the cuttings from drying out, but only water the soil when it starts to look dry.
If there are larger branches you would like to propagate as bonsai you could consider air-layering. You should do this after the first flush of growth has hardened off in late spring.
Air layering is performed by removing the bark and cambium layers of the branch, revealing the underlying xylem tissue. This allows water to flow up the xylem and hydrate the foliage, but sugars created by the leaves will accumulate where you cut the phloem and bark away.
If you wrap the area with sphagnum moss and a small container or bag, you can then water as necessary and wait for roots to develop. You can usually cut the branch away and plant it in autumn, or if there are not enough roots you can wait until the following year.
Cotoneasters can also be propagated from seed, but be aware this will take much longer for you to have a usable bonsai specimen.
Cotoneaster bonsai care
I hope you'll agree that Cotoneaster is an awesome species for bonsai and you can take this knowledge to care for your bonsai with confidence. Bw sure to follow us on social media and sign up to our mailing list to keep up to date with all our releases.
Cotoneaster bonsai FAQs
Can you grow Cotoneaster bonsai indoors?
Cotoneasters will struggle to survive indoors due to lower light and humidity levels. I recommend only trying to grow Cotoneaster as an outdoor bonsai.
How fast do Cotoneaster bonsai grow?
Cotoneaster grow at a rate of 20-40cm per year as a ground or hedging plant. When placed in a bonsai pot to restrict growth, this will be much slower.
Can I grow Cotoneaster from cuttings?
Yes, cuttings are a great way to propagate Cotoneaster. I recommend softwood cuttings in late spring or early summer.
When should I trim Cotoneaster?
Cotoneaster can be trimmed throughout the growing season, but you should only prune growth where leaves have hardened off.
Do Cotoneaster have thorns?
No, Cotoneaster trees do not have thorns.
Are Cotoneaster berries poisonous?
Cotoneaster berries can cause an upset stomach if consumed. They have the potential to cause something called cyanogenic glycoside toxicity if consumed in large quantities, but it is rare for severe Cotoneaster poisoning to occur.
Does Cotoneaster lose its leaves? Is Cotoneaster deciduous?
Cotoneasters can be either deciduous or evergreen. It depends on the sub-species and the climate you live in. If you live in a colder climate, it increases the chance your Cotoneaster will drop its leaves over winter.