As a collector of Japanese maples for decades, and being one that enjoys growing most of them in pots here in my Southern California gardens, I learned that the single most important factor in growing healthy Japanese maples in containers or pots is the soil. So I'm going to talk about soil first. 

Your Japanese maple's vitality starts with the health of its root system. The planting soil mix is the foundation for building a strong root system which in turn will help to develop a healthy tree.

Early on in my adventure with growing Japanese maples, I experimented with various types of materials in an effort to create the "perfect recipe." These days, I'm using a simple recipe that combines a few products for your soil mix, which will provide your Japanese maple with the right amounts of water, air, nutrients, and the stability they need to grow well in pots or containers.


The most important functions of a good soil mix:

  1. Drainage. Japanese maples like moist but not wet soils. Constantly soggy soil will lead to root root rot, which is the most prevalent killer of Japanese maples in containers, and in the ground. The soil mix should hold water evenly throughout the container and allow for goo drainage.

  2. Nutrient Retention. The mix has to have the ability to retain nutrients applied while facilitating the roots ability to absorb them and distribute these to all parts of the tree.

  3. Support or Stability for the Roots. A good soil mix will provide conditions for development of a strong root system. A strong root system will result in a stronger tree that will stand up to inclement or windy conditions. 

It is best not to use native soil (dirt) from your landscape/garden as it can contain soil born pests, diseases, and smaller particles, such as in clay soil, that will become compacted, hindering the mixes draining ability in the container. Native garden soils are also heavier; holding more water and adding to the potted plants weight , which makes it harder to move. I also elect not to use bagged planter or top soil mixes that contain fertilizers. These planting mixes are formulated for general overall garden plantings and may not have the best of nutrient percentage for a Japanese maple. I also stay away from potting mixes and soils that contain chicken or cow manures as the nitrogen in them can burn roots. The Japanese maples require very little fertilization. Because of this I would rather feed my maples with nutrients when I feel it is needed.



My Potting Mix Recipe

Depending on the size container I'm planting in, I use a meauring cup, coffee can or small bucket to make the following mixture:

3 Parts Quality Potting Soil - Use a quality potting soil - not one of those $1-a-bag low-grade potting soils you might find at a box store. The one I use costs about $4 for a 20 quart bag.

2 Parts Fir or Pine Bark - Small orchid bark or mini pine bark chips. These barks have a slightly acidic pH value and will aid in moving alkaline soil to a neutral or slightly acidic value. Also helps to retain nutrients over an extended period of time and keep soil open for better drainage.

1 Part Pumice - Pumice is an excellent soil conditioner, as it is highly porous providing excellent water, air, and nutrient holding capabilities. Pumice will not decompose or compact over time and is very lightweight. Agricultural grade pumice can usually be found at local feed stores as a product called Dry Stall. The particle size is about 1/8". It's a good idea to wash the product before use to remove the fine particles. If you can't find Pumice you can substitute with perlite.

Fertilizer - You can buy a low-release fertilizer, such as Osmocote, and add it to soil mix as per package instructions.

Okay, now that we've addressed the most important thing about growing Japanese maples in containers: the soil, we'll move on to the next most important thing...



Choosing A Pot Or Container

Growing Japanese maples is extremely rewarding, but growing them in containers adds a wonderful dimension of versitility to this plant. For myself, and many others, the ability to easily move this beautiful plant throughout the garden, patios, decks and entryways make it even more valuable.

Things to consider when choosing a container...


Size Matters
The most important thing when choosing a container to grow your Japanese maple in is size. Choose one that will allow the tree's root system to grow for two to three years before moving up in size. Japanese Maple has a fairly shallow root system and does not require as deep a container to grow in as other trees.


Shape Can Be Flattering
Next thing to consider would be the shape of your container. The shape of the container is both important to the plant and to yourself. Does the shape of the container allow the tree to be easily removed from the pot in a few years without damaging the root system or pot? Avoid vase-like pots with narrow tops. The top of the pot should be as wide or wider than the bottom of the pot. You might need to remove the pot in order to root prune your maple every few years to control its size or to facilitate healthy root growth. 


Drainage Holes Are All Important!
Does the pot have sufficient holes in the bottom for good drainage? One 1/2- to 1-inch hole in the bottom is usually good enough, however two or three holes will work better. Drill additional holes if necessary to provide adequate drainage. 


Before adding the soil mix inside the container, I have found that using a piece of polypropylene shade cloth or porous landscape fabric to line the inside bottom of the container to cover the drainage holes works extremely well to keep the holes from becoming stopped up with soil, and adds no weight to the pot.




Wind Is A Concern
Is the bottom of the pot wide enough to support the tree in wind? You don't want a pot with a very narrow base as it will be prone to tipping in the wind, especially with upright Japanese maples. You can add a brick or stone to the interior bottom of any container to increase stability, however keep in mind that this will make the container heavier for transporting.


Pot Weight
Do I need a lightweight container that can be tranported more easily? The material is also a factor to consider if it will be moved at times. Clay, ceramic, and concrete pottery are typically much heavier than plastic or fiberglass. Clay, ceramic, concrete and double walled plastic or fiberglass containers provide better insulation from freezing and hot conditions.


Color And Style Matters
Not only will you want to pick a color of container that goes well with the foliage and bark colors, and texture, of your Japanese maple, you'll also want to pick a style that matches the style of your home or other structures or the other plants in the surrounding environment. Many nursery & garden centers offer a wide variety of containers to choose from. Before heading out to buy a container, take pictures of your home and the surrounding environment. Doing so will help you to choose just the right color and style. 

If you'd rather not dump your dollars into a more expensive container, just about anything you can find that holds soil and drains well is a potential container for a flower garden.

I sometimes use nursery pots. These are those black or other colored containers that larger shrubs or trees at your local nursery and garden center are growing in. I look for what is called a "Squat Pot," which is a pot that is shorter and wider than it is tall. These plastic containers are lightweight and strong, and often have handles on the top rim that make for easy lifting and moving. The main draw back for many is their color and simple shape, but, for those with a creative mind, modifictations can change the look. Painting, covering with outdoor fabric or setting this container inside a decorative pot are just a few ways to go about sprucing up what might otherwise be a drab container. Trees planted in these growing containers can also be set in the ground throughout landscaping or gardens when desired. When setting a container in ground remember to fill a couple of inches around the container with sand or gravel to keep surrounding soil from plugging drain holes and to allow for easy removal of container.



Planting In The Container

Step 1
Before filling your container with the soil mix, line the bottom of the pot with shade cloeth or a porous landscape fabric. This will keep the drain holes from becoming stopped up with soil. 

Step2
To remove your Japanese maple from the container it was growing in, grasp the tree firmly by the base of it's trunk and gently lift and remove it from the container it was growing in. If the root ball is stuck in the container either cut the container away or place the tree on it's side and gently pound on the side of the container to loosen the root ball. After having removed the tree from the container, very gently loosen some feeder roots around the surface of the root ball. If rootbound, you can gently spray the sides and bottom of the root ball with a stream from a garden hose to remove a little soil from the exterior of the root ball, making it easier to loosen roots.

Step 3
Pour a small amount of your soil misture in the bottom of the container. Set plant in container and make necessary adjustments by adding or removing some soil mixture so that the top edge of the root ball will sit 1/2 to 1" below the rim of the container.

Step 4
Backfill with potting mix around rootball, tamping as you go, until the the level of potting mix is even with the top edge of root ball.

Step 5
Water thoroughly until water starts to drain from the holes in the bottom of the container. Add more potting mix if settling occurs during watering.

Step 6
Apply a 1/2" layer of wood chips or spaghnum moss to soil surface - maybe stone chips or gravel if you'll be planting succulents or other small plants around the base. I've found that creeping groundcover or crevice plants such as Blue Star Creeper, Creeping Jenny or Dwarf Mondo Grass make nice soil covers in Japanese maple container gardens. 



More Tips

Now that your Japanese maple is planted, it's time to add a few items that can make the experience of owning and growing  a potted Japanese maple even more enjoyable.
 
Here's a few tips...

  • Using a tray or Surface Saver under your pots will protect your patio and deck surface from staining and scratching. These also allow your container to drain more efficiently.

  •  Another item that is worth every penny and also keeps the pot off the surface, but allows you to move or roll your heavier pots is the pot caddy. They come in many shapes, sizes, materials, and number of castors (wheels). Many of the caddies or rollers have built-in trays. Make sure these trays have holes in them as you never want your Japanese maple sitting in water.

Hopefully the tips in the article have provided you with the  needed to successfully grow healthy Japanese maples in containers. Japanese maples are easily grown. When their few needs are met they'll reward you with a beautiful, low-maintenance tree that will greatly enhance the overall appeal of your landscape and gardens. There just aren't too many other trees that have so much to offer to your gardens. No other tree or shrub has ever given me the rewards I've recieved from my container grown Japanese maples. 

Just a few last words of CAUTION; Japanese Maples Can Be ADDICTING.