The North American native Thuja plicata ‘4Ever’ is looking particularly stunning in the garden this summer. Of all the forms of Thuja plicata we’ve trialed, this is undoubtedly the brightest. Reportedly maturing at 12′ tall x 3.5′ tall, I’m left to wonder what they used the measure the size. Our 4 year old specimen is 5′ tall x 5′ wide. Based on the current growth rate, we’d expect 12′ tall x 12′ wide in 10 years, so if you’re looking at “forever”, I’d probably put these on 15-20′ centers.