You won't get a mass effect because these are all unnatural looking colored foliage varieties that are noticeably different from one another. Space them out as individual specimens (accent points) with plenty of room for each. Dimensions listed vary because the plants vary from one site to another in how they develop on that site, also there is always a time element involved - some sources may be estimating typical size for a certain period of comparatively few years (often this is 10 years) while others may be attempting to indicate how big a fully developed one might be.

Mass planting is planting a large number of the same kind in one area. Using one kind in a large quantity evokes natural populations filling a meadow or covering a hillside. Where large numbers of marigolds, hybrid bush roses other stylized plants are used these are conventionally planted in geometric patterns in formal layouts with clipped shrubbery and the like for the same reason - these look out of place in informal planting. Wild-type green seedling Japanese maples could be mass planted to simulate a natural stand in the wild where these might appear as an understorey layer beneath taller trees, as vine maple does here in the PNW. In a woodland garden some purple ones could also be included for contrast.

I might add with all three of those cultivars it would be good to give them abit of extra protection from both cold winter winds ( Katsura and Japanese Sunrise) and too much summer sun ( butterfly)..they are three of the less hardier specimens from both my experience and many others who have posted here ...Good luck you have not picked the easiest of cultivars to grow in a not "perfect" jm area although with lots of attention you may dio alright

...and yes three trees do NOT make a mass planting and your spacing questions are probably not knowable since as BB said there are too many variables...I agree with him grouping these three together is probably not the best idea and seems to me a bit of an odd idea... better placed as specimen plantings ...but that is only my opinion and bb's suggestion ...you may have differnt and valid tastes ..David

I'm going to quote J.D. Vertrees- "In various types of mass plantings, it may be advisable to include two or more cultivars or species possessing outstanding features to insure a bold effect through each season" He goes on to mention Katsura and Sango Kaku, which is similar to Japanese Sunrise. So, this "odd idea" comes from an expert. The picture underneath shows this done to beautiful effect, and I've also seen it done in garden books as well. I have alot of room and plan on mixing in evergreens, azaleas, ect. for a Japanese garden effect. Mountain maple also suggested planting Katura and Japanese Sunrise next to each other, for the beautiful effect of their fall foliage colors together.
They will be planted against a 7 foot fence, so hopefully that will help with wind. Just was curious if these trees really did get 15 feet wide, or if I could get away with 10
. I guess you both answered that, in that its not knowable so I will stick to a further distance to be safe. Thanks for the advice. Judy

That's called accenting. There is a large grouping of green or otherwise not abnormally conspicuous ones that is then set off (accented) by the inclusion of a couple brightly colored or otherwise conspicuous ones. It is not the same as the whole planting being variegated or bright orange etc.

Yes mixing specimens plants with "mass plantings" for accent and color break up of Jm's.... is not the same as ONLY planting three of one or similar cultivars...what you are doing is "minimum" planting accent trees amoungst other garden trees and bushes not a mass planting of JM's...although if you want to think of it as that I certainly am not one to qibble ;>) ... David

I guess I have been misunderstood- I want to start a mass planting, and again have the room for it. I am starting out with these three cultivars, and am putting them against the backdrop of some mature trees, which are against a fence. Since they are an understory tree, if thats the correct word, I thought the dappled light would be good for them. In the picture I have referred to, there are a number of different Japanese maples in the foreground, and the caption reads mass planting of acer palmatum in the landscape. That is the effect I am after, and I don't really care what its called. I am only starting out with 3 trees because thats all I can afford right now, but the fence runs the length of an acre, so I guess eventually it will be a mass planting of maples, because eventually I would like it to look like the photo in Vertrees, which shows about 10 JM trees. The azeleas and small evergreens would go in the foreground of the bed. I really liked the fact that the picture didn't look like a row of the same tree, but was greatly varied in its leaf colors and textures. Hopefully you guys have access to this book, and can see what I mean. I really didn't mean for this to turn into a debate about my taste in arranging cultivars together, I just mentioned them so people could help me with size. I sort of get the idea you guys think I have no taste, and do not understand what the book was explaining, or how to garden, which has hurt my pregnant hormonal feelings-not meaning to qibble. Again, thanks for the advice.

No boddy have answered your question. I do lime to know : what is the minimum space between two JM planted together?? Some body knows? I just bought two Sango Kaku jm. I want these trees close each other because I'm planning to place a modern concrete-wood outdoor bench in the backyard. Thank you ! Hopefully somebody answer.

Thank you! I'm in zone 5, Illinois. Thank you very much. I found out from a gardenist. Minimum you could plant a JM that can reach 12'-18' tall from each other 8' - 12'. I want canopy like, so he said 10 will be the ideal.

Just to clarify, JM 12'-18' tall and separated from each other, would be minimum 8'-10' apart. I want canopy like, so 10' be ideal.

I would go 15 to 25ft. Ten feet is too close in my opinion. A tree that is 10 ft wide planted 10 ft apart will grow into each other pretty fast. Most Japanese maples get much wider than 10 ft.

For our IL zone 5a/b, Sango Kaku (or coral bark maple) is not winter hardy to be planted in ground. Many people in our area tried but have not heard any success story. You may want to put these two Sango Kaku in containers and winterize them in unheated garage.

there are other cultivars that are hardy to zone 5, green or red leaf, upright or weeping.

Vivian_2010, you are absolutely right. lots of people have told me the same thing. I'm going to take out of ground and put in containers and winterize in my garage . Thank you to all of you, and yes 15' to 20' separated looks better, since I have already a flower bed in middle of my backyard.