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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.
Mature height and width measurements for newer conifer cultivars seem to be wildly inaccurate. We have a 4 year old Larix ‘Iron Rod’ which the seller lists as 10′ X 3′ in 10 years. It is already approaching 8′ wide and, while beautiful, may need to be removed. This is not the first conifer cultivar we’ve had to cut down because it has overgrown the space we allotted. And it is always the gorgeous specimens!
Hi,
When planting, I always have trouble giving adequate spacing to accommodate mature plant needs. I’ve consistently planted things too close together.
So can I ask, how did you come up with the 15-20′ on center spacing? (Did not follow the math.)
I would have (erroneously) guessed that for 12 ft. wide plant, that would give 6 ft from center of plant to edge of plant. Or 12 feet apart on center. Would you do the same?
Are you just being very generous in your recommendation, given the “forever” timeframe, or is there some other math wizardry I’m ignorant of?
Would love to know how to better space plants to allow for mature growth. Hope you can help.
Thanks!
Mary
Great question. Since our 4 year-old plant is already 5′ x 5′, we would expect, based on experience, for that size to at least triple in the next 8 years to 15′ x 15′. We find that at that age, Thuja plicata stops growing in width…at least on the East coast. We strongly urge people to visit botanical gardens and where possible see mature plants actually growing.