Perhaps some of the decorative Junipers would be a better fit for the size you mention.

Yew (Taxus species) soft foliage and can be maintained/pruned at any height.

Thuja (arborvitae) same as Yew.

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Pines/fir/spruce: won't take to pruning.

Juniper around kids will be scratchy, irritable to skin, & hurt.

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Dax

hi helen

are you really wanting ONLY pine..???

i have met peeps who call all conifers .... pines .... especially when they try to understand that NOT all conifers have PINE cones ...

frankly.. you dont have enough room for most pines.. that will get tall enough to do what you want ... they are famous for being as wide as tall ... and by that time... they might eat the playscape ...

and.. no tree really ever stops growing at some magical height.. so there is nothing that will stop at your 20 feet.. its all about annual growth.. how long it takes to get to 20 feet.. and then to get to 40 feet ... etc ...

most size ESTIMATES are at 10 years ... and they will be twice as big at 20 years ....

for tall.. thin.. and little or no pruning.. looks into Thuja occidentalis 'Degroot's Spire' .. insure you buy single leader plants .. or trim them to such ...

they grow around a foot per year...

and i would not go much bigger than 3 foot ... at purchase ...

and they will probably be pot bound... so if you get toward planting.. check in with us.. and we can teach you that part ...

i would not plant them in summer.. if you cant get them by spring.. then wait until fall planting season ....

ken

Here is a link that might be useful: link

Thanks for the direction - was hoping there was a form of pine small enough, but it doesn't look like it.

It looks like Degroot's Spire grows a little on the slow side. What about 'Emerald Green' Arborvitae?

'Emerald Green' is a synonym for 'Smaragd'.
The 'Smaragd' and the 'Degroot's Spire' do have the same growing rate...