Japanese maples need an acidic, well-draining soil. I would direct you to the Container Gardening forum to reveiw discussions about Al's (tapla) "gritty mix" which, with the exclusion of any lime component, is pretty much ideal for growing JM's. The alternative is to locate a durable (read: chunky) acid loving potting soil - this is a common product in my area but have no idea how easily located in the more arid and alkaline soil-based SW.

You may also need to acidify your irrgation water if it too tends towards alkaline conditions. A tablespoon or two of household vinegar in a watering can will do the trick.

In your climate, you will need to pay close attention to watering (perhaps even a couple times of day for that size container in the heat of summer) and be sure to keep out of the sun during the hottest part of the day.

It is a myth that Japanese maples require an acidic soil. Neutral to slightly acidic is preferred, with PH of 6.0 to 7.0 being the ideal range, but soils as alkaline as 7.5 are fine too. There is certainly no need to treat them like Camellias or Azaleas.

Perhaps they do not require an acidic soil but, like the vast majority of plants, they will certainly prefer acidic soil and will tolerate very acidic soils. Alkaline soil conditions - like what is present in much of the southwest US - poses challenges for gardeners attempting to establish these trees in those locations. And since the OP is going to be growing it in a container, why not provide what is easiest and best for the tree? Bark-based potting soils tend to be acidic and provide the durability and good drainage/high aeration that these trees do require.

It is irrelevant to worry about the PH of commercial potting mix with regard to Japanese maples. The PH of all these mixes will be in the ideal range for Japanese maples. Also, if making and using Al (tapla)'s gritty mix, no need to avoid adding lime.

Worry about the drainage/aeration, yes, the PH no.

And yes, bark-based mixes (preferably softwood bark) are usually pretty good for Japanese maples.

Not trying to hi-jack your thread, kurt, but thus far I have received no responses to my thread requesting info on growing Japanese Maples in a container.

I, too, am going to try to grow a JM in a container, since I have had little luck trying to grow them in the ground - Colorado is not ideal Japanese Maple country, to say the least. The above two posts talk about using a "bark-based mix" for this.

I know that there are orchid mixes that are obviously bark based, but is this what you are talking about using? Is there some other sort of commercial potting soil that would fit the bill, or are you indicating that you need to make your own potting soil mix. If the latter, could you elaborate on this, as in, what ingredients should be used and at what approximate percentage of each ingredient? (Or a link to this info would be fine, naturally. :-) )

Holly

This is the recipe that is most often recommended for long term container plantings, including any type of tree:

1 part uncomposted screened pine or fir bark (1/8-1/4")
1 part screened Turface
1 part crushed Gran-I-Grit (grower size) or #2 cherrystone
1 Tbsp gypsum per gallon of soil
CRF (if desired)

This is what is commonly referred to as "gritty" mix - it is extremely durable (holds up long term) and provides both fast drainage and excellent aeration.

Depending on where you are located and the suppliers that service that area, it is possible to purchase a suitable bagged potting mix that very closely replicates the texture and durability of the above recipe - Kellogg Garden products makes such a mix (sold under a couple of brand names) that is intended specifically for trees, conifers and most broadleaf evergreens. But be aware that most prepared, bagged potting soils tend to be comprised of too fine particles and are too moisture retentive and therefore too liable to compaction or collapse.

Growing a JM in a container is a bit more complicated than growing one in the ground. More attention is necessary with regards to watering and fertilizing, there will be a need to be aware of and make provisions for winter protection in cold winter climates (anywhere zone 6 or below) and there will be a need for routine periodic root pruning and repotting. And while I agree there is less of a need to focus on adjusting pH for JM's with a container soil mix, in areas that tend towards alkaline water sources - much of the southwest - I would recommend you neutralize or slightly acidify the irrigation water with household vinegar (1-2Tbs per gallon).

There is a search function at the bottom of each GW forum page that can facilitate looking for additional info on both growing in containers and more specifically, growing JM's or other trees in containers. Just type in the topic and the results will pop up. I'd suggest you search this forum for other discussions of growing JM's in a container - there have been many over the years - and the Container Gardening forum for a broader approach, such as growing trees in containers, how to fertilize and with what and general container growing topics.

And I'd suggest you start with the following attached link. It is probably the most widely read and responded to thread in the history of GW, written by a recognized authority on container gardening and containing a vast wealth of information.

Here is a link that might be useful: Container soils - everything you need to know

Thank you for that info, gardengal. So basically, the potting soil mix recommended for containers doesn't actually have any soil in it?? Amazing...

Holly