Bonsai trees, evocative of nature, are much more compelling than the average houseplant and lend a feeling of peace and enjoyment. Many people looking to purchase a tree wish to keep an indoor bonsai. But how can you tell which trees are suitable as indoor bonsai trees vs. those that need to be kept outdoors?
When people hear that I have bonsai, they often ask “can I keep bonsai trees inside?” In this article, I will discuss the differences between keeping bonsai indoors vs. outdoors, as well as basic horticultural demands so that irrespective of your living situation, you are able to keep your newfound bonsai healthy and happy.
Is An Indoor Bonsai Tree the Best Option?
Here are the basic pros and cons of indoor & outdoor trees, but if you’d like to understand the reasoning behind them, as well as my plant recommendations, keep reading.
Indoor Bonsai Trees
- Good for people without patio or yard space
- Improve home ambience and aesthetic
- Easier to enjoy
- Limitations of useable species
- Weaker than outdoor trees
- Slow growth and development
Outdoor Bonsai Trees
- Greater diversity in species you can use
- Stronger trees, faster growth
- Requires outdoor space
- More frequent watering and maintenance
Can You Keep an Indoor Bonsai Tree Healthy?
To begin I wanted to discuss the core essentials that keeps a plant happy:
- carbon dioxide
Thinking back to your biology class in high school – CO2 enters the leaves, water goes up the roots, and sunlight fuels the photosynthesis process.
Seems simple right?
But when you start introducing variables like humidity, lighting, environment, and soil it becomes harder to meet the essentials. Additionally, there is a 4th criteria—oxygen. In order to use the sugars the plants produced in the day they must consume oxygen in a process called respiration: sugars and oxygen gets consumed and in turn creates energy for the plant.
So how does this all tie into keeping bonsai indoors vs outdoors?
Let’s think about how the respective environments influence these variables.
The average living space is lit with ambient and artificial lighting. It’s easier on our eyes and creates a more relaxing environment. Windows and blinds cut the intensity of light as well. What does this mean for the tree?
It’s receiving significantly less photosynthetic energy compared to a plant kept outdoors. Generally speaking, this means a weaker tree.
Well, how about artificial lighting? Common fluorescent and incandescent bulbs can’t provide the spectrum necessary for strong photosynthesis. There are grow specific lighting available but can be costly.
This is often an overlooked concern. The humidity levels indoors relative to outside are often much lower. This means transpiration is occurring at a much faster rate on your indoor bonsai trees. Some species are more tolerant of this and others risk desiccating and dying.
Well, should I just water more? No!
To be discussed in further depth in the next section, overwatering can displace oxygen necessary for the health of the roots and the entire tree. What we can employ is misting.
By misting your tree a few times a day you can greatly reduce transpiration stress. For an arid outdoor environment such as those in the high and low deserts misting is very effective.
Water & Oxygen
To keep the roots of your tree healthy they need both water and oxygen. Too much air could mean your roots dry up and die. Too much water and all the oxygen surrounding the roots will be displaced.
The soil of trees kept indoors dry at a much slower rate. With this in mind you should adjust your bonsai watering accordingly. Put simply, you water when the soil is dry and you don’t when it’s wet.
A good way to check is to dig your finger down the first inch of soil. If it feels damp do not water. A general rule of thumb for common nursery soil is to water every 3-4 days. For the same tree outdoors you may be watering every 2 days. This can change depending on your climate and bonsai soil you use.
Do you live in a cold environment with below freezing and sometimes subzero temperatures? Contrary to popular belief most trees are very tolerant of the cold and require it for a proper dormant period.
But if you live where it dips significantly below freezing it may be advisable to provide winter storage for your trees. For tropical trees such as ficus this means bringing it indoors. For deciduous and some coniferous species, you can place them in an unheated garage.
What you should avoid is bringing truly cold hardy species like junipers indoors which may delay or interrupt dormancy. Dormancy is important—just as people need sleep to function for the day, plants need dormancy to prepare for spring.
Gauging the Success of Your Indoor Tree
It is still possible to grow bonsai indoors. In addition to employing all the suggestions listed above, the biggest way you can influence the success of your new bonsai by good selection of the species. Some varieties will be more tolerant of the “harsh” indoor growing conditions and could even thrive.
To set a criterion for picking indoor bonsai trees, lets look at some common indoor house plants and understand why they successfully grow indoors.
The snake plant is a popular and common variety seen in homes and offices. The tree is of tropical origin meaning they tolerate and prefer warmer temperate conditions.
Orchids are another popular houseplant for their ornate colorful flowers. What these 2 houseplants have in common are their thick fleshy, waxy leaves. This feature allows them to be more tolerant of varying humidity and moisture levels in the soil.
Making the Choice
Now that you know the environment you’ll need to create for your indoor bonsai tree, it’s time to make a decision.
Here are a few recommendations for both indoor, and outdoor bonsai.
These trees are easily found in almost any garden center and are extremely adaptable growing throughout the entire US. They make a good introduction to coniferous species and are easier to care for.
If you’re a fellow deciduous lover and enjoy the changing seasons, tridents are a great choice. They’re fast growers and leaf size is naturally small. It’s more challenging to grow than procumbens due to fungal and disease susceptibility but overall a strong choice.
Do you live in some of the colder regions of the US? An alternative to trident maples are amur maples. Indigenous to Northern China and Russia cold tolerance is in their blood! As far as deciduous species go they are a strong fast grower but susceptible to chlorosis. If that happens just apply iron fertilizer.
Indoor Bonsai Trees – Recommendations
Ficus leaves bear the thick and waxy quality making them tolerant of indoor humidity levels. Additionally, they are a vigorous species that will be more tolerant of abuse and will develop much faster than most trees.
Dwarf Jade is my second recommendation. These are actually succulents but the naturally small occurring leaves can create very convincing bonsai. Additionally, these trees are very tough and hardy so you’d really have to try if you wanted to kill one. To show their potential as bonsai here is one dwarf jade on display at the Pacific Northwest Bonsai Museum:
My final tip and piece of advice is to just go for it. Bonsai encompasses many elements: aesthetics, art, horticulture, and art to name a few. Understanding and learning the different aspects of bonsai take time.
The hardest thing people struggle with when starting bonsai is keeping them healthy and alive. My intent with this articles is not just to tell you what to do but to convey understanding behind the concepts. I hope they can aid you in making an educated choice when you decide to purchase and care for your first bonsai!