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niroha

Size of Container for JM

niroha
14 years ago

Hello. I am new to the forum and hoping for some guidance.

Actually before I go any further I should mention I am new to gardening. This is our first yard so this is my first go at any real attempt at gardening. So definitely put a 'novice' tag on my forehead.

I love love love JM's. I have ordered a few and the ones going in the backyard are going to be in containers for a few years before they find a permanent home in the ground. I've read some conflicting information on the size of container needed JM's. I'll be using cedar containers, I just need to know which size to pick up!

The JM's going in containers will be:

2-3 y/o Ukigumo

2-3 y/o Inaba Shidare

3-4 y/o Katsura

3-4 y/o Beni schichihenge

I would also like to put some ground cover plants with them in the container - putting that out there in case that affects the size of container I should seek.

Oh one last question - recommendations for the type of soil I should pick up?

Thank you very much!

Comments (5)

  • gardengal48 (PNW Z8/9)
    14 years ago
    last modified: 9 years ago

    An 18-24" square box should hold you for several seasons :-) That size will actually be suitable for a longer period if you repot and root prune periodically and are willing to accept a reduced growth rate.

    I grow a great many JM's in containers long term and the potting mix I prefer is Gardner & Bloome Acid Planting Mix. It is properly chunky with a high proportion of bark, so provides the required drainage yet holds up well long-term. It is recommended for containerized JM's, among other things. It should be available at any better nursery in the Seattle area (Swanson's, Sky, Emery's, Molbaks, etc.).

    You will also need to pay careful attention to watering and fertilizing containerized maples. I generally use Osmocote when potting up initially and once or twice a season in spring thereafter.

  • niroha
    Original Author
    14 years ago
    last modified: 9 years ago

    thanks for the response. I'm heading over to swansons this weekend so I'll look for that mix. How much growth will a container restrict long term?

  • gardengal48 (PNW Z8/9)
    14 years ago
    last modified: 9 years ago

    Depends on the size of the pot, the size of the tree and how long you keep it in a container :-) Container gardening of woody plants is a natural dwarfing process - anything that limits the root run of the tree will reduce rate of growth and ultimate size.

    btw, several local nurseries carry an excellent selection of Japanese maples so you should not have to order plants from elsewhere unless you are looking for something very rare or unique. Buying locally supports our local independent nurseries and eliminates shipping charges. Two that I think have the best/largest selection are Emery's and Wells Medina.

  • niroha
    Original Author
    14 years ago
    last modified: 9 years ago

    Thank you for the local nursery tips! I have not been in to those nurseries and I will definitely be sure to check them out.

  • tapla (mid-Michigan, USDA z5b-6a)
    14 years ago
    last modified: 9 years ago

    You may find something interesting in the following. It's a copy/paste job from something I wrote in another forum:

    How large a container should be, or CAN be, depends on the 3-way relationship between plant mass, container size, and soil type, assuming correct watering habits. We often concern ourselves with "over-potting" (using a container that is too large), but "over-potting" is a term that arises from a lack of a basic understanding about the 3-way relationship noted, which should logically determine appropriate container size(s).
    It's often parroted that you should only move up one size in containers when "potting-up". The reasoning is the soil will remain wet too long and cause root rot issues, but it is the size/mass of the material and soil type/composition that determines both the upper & lower limits of appropriate container size - not consecutive volume progression.

    Plants grown in slow soils need to be grown in containers with smaller soil volumes so that the plant can use water quickly, allowing air to return to the soil. This (smaller soil volumes) and the root constriction that accompanies it will cause plants to both extend branches and gain o/a mass much more slowly - a bane if rapid growth is the goal - a boon if growth restriction and a compact plant are what you have you sights set on.

    Conversely, rampant growth can be had by growing in very large containers and in very fast soils where frequent watering and fertilizing is required - so it's not that trees rebel at being potted into very large containers per se, but rather, they rebel at being potted into very large containers with a soil that is too slow and water-retentive.

    We know that there is an inverse relationship between soil particle size and the height of the PWT in containers. As particle size increases, the height of the PWT decreases, until at about a particle size of just under 1/8 inch, soils will no longer hold perched water. If there is no perched water, the soil is ALWAYS well aerated, even when the soil is at container capacity (saturated).

    So, if you aim for a soil (like the gritty mix) composed primarily of particles >1/16", there is no upper limit to container size. The lower size limit will be determined by the soil volume's ability to furnish water enough to sustain the plant between irrigations. Bearing heavily on this ability is the ratio of fine roots to coarse roots. It takes a minimum amount of fine rootage to support the canopy under high water demand. If the container is full of large roots, there may not be room for a sufficient volume of the fine roots that do all the water/nutrient delivery work and the coarse roots, too. You can grow a very large plant in a very small container if the root have been well managed and the lion's share of the rootage is fine.

    *****************************************

    FWIW - Research shows that root congestion begins to stunt growth about the time the roots have colonized the soil mass the the degree that the entire soil/root mass comes free of the container when you lift the plant. see Plant Production In Containers II, by C Whitcomb PhD) He also notes that this becomes a permanent issue unless you bump the plant before it becomes root bound beyond this delineation. To eliminate the effects of tight roots, root-pruning is required at repot time.

    If you think about it, the only reason bonsai are able to live and remain healthy for 100s of years in small containers is because of the careful attention to roots.

    Al

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