you either want privacy.. or you want spacing..

you have set your own dichotomy ...

how are we to decide for you???

check out the link for pix of older specimen .. easily 30 feet by my eye ...

ken

Here is a link that might be useful: link

Looks like 9 feet apart in that one photo! So they have no problems touching or contending for water? That is my worry. If they play fairly when close to each other.

the issue of close planting.. is usually about divergent size ...

when they are planted close in time.. and close in size.. like 3 brothers.. they tend to grow up together.. and get along ...

but when you try to add the third set.. say.. a late life baby ... then perhaps the older two.. will not play fair with the babe ...

i do NOT recommend you go shop out another set of 15 footers ... too big for transplant.. in my world ....

but if you go in the 6 to 8 foot range.. and since the others have only been there 3 or 4 years.. you should be able to slip in another set ..

if on the other hand.. they had been there 20 years.. i bet you would have problems.. inter-planting them ...

make any sense???

one thing you did not mention is if the old will block the sun on the new set ... shade them out????

ken

Well they do perfer sun so they will shade eachother on the interior.

Given adequate moisture they put on growth fast...including width.

I fit this one in my SUV and three years later it would need a box truck to haul it.

{{gwi:341811}}

Birches often occur in groves in nature. When you buy them grown in clumps if there is much open space around them the stems lean away from one another over time, to produce a visual tension (they look like they are falling over). So it is actually preferable with clumps to have others close enough to shade the sides and keep the clumps upright. A naturalistic arrangement would be mostly single stemmed specimens with a few clumps here and there.

River birch is not a small-growing tree. One in Seattle (USDA 8) had an average crown spread of 98' during 1992. Another, on the same property measured 86' across the same year. In 1987 one in a park in a city elsewhere in the Seattle area was determined to have an average crown spread of 87'. These were all or nearly all (can't remember the exposure being received by the third one) specimens growing in the open on bottomland soils.

So, yes, when not densely crowded these grow 30' wide - and then some, by quite a bit.

AHHHH - thanks a ton. I was wondering about the 30 foot thing. Great info everybody. I had an idea but was unsure if I was correct. So many people plant trees close to houses or right next to each other because they are so small and then say "we have no problem". well yea - they are 10 years old - I'll check back in another 20 years!! LOL

Most people select and place trees and shrubs as though they were static objects like tables and chairs. Elements of the trade pander to this mindset by attributing impossibly small "mature" sizes to them.