Crimson Sentry Norway Maple Tree

‘Crimson Sentry’ is a narrow, slow-growing Norway maple with dark purple-maroon foliage. Its upright crown takes less ground space than ‘Crimson King’, though mature-size estimates vary considerably among sources. ## Form and seasonal interest Oregon State University records it as a bud sport of ‘Crimson King’, selected at A. McGill & Son in Oregon in 1970. It received U.S. Plant Patent PP03258 on August 22, 1972 ([patent record](https://patents.google.com/patent/USPP3258P/en)). Its dense crown begins columnar and broadens to a pyramidal or oval outline. Small yellow flowers, sometimes tinged dark red, appear in spring; the leaves are purple-maroon and turn reddish bronze in fall. [Van den Berk Nurseries](https://www.vdberk.co.uk/trees/acer-platanoides-crimson-sentry/) also describes dark red summer leaves and April yellow-green flowers. ## Siting and mature size [Oregon State University](https://landscapeplants.oregonstate.edu/plants/acer-platanoides-crimson-sentry) gives about 7.5 m tall by 4.5 m wide, and [Kansas State University Extension](https://www.maraisdescygnes.k-state.edu/lawn-garden/popular-lawn-garden-publications/trees-shrubs-and-woody-vines/ShadeAndOrnamentalTreesForKansasmf2688.pdf) lists 20–25 ft tall. The [RHS](https://www.rhs.org.uk/plants/46362/acer-platanoides-crimson-sentry/details) reports an ultimate 12 m by 5 m, while Van den Berk gives 8–10 m by 6–8 m. Allow for the larger reported crown. Site in full sun or partial shade and moist, well-drained soil. Oregon State notes powdery mildew can be conspicuous in western Oregon in mid- to late summer; a breezy site may help. Norway maple and its cultivars are specially regulated in Minnesota, where seedlings should be controlled ([Minnesota DNR](https://www.dnr.state.mn.us/invasives/terrestrialplants/woody/norwaymaple.html)). ## Maintenance Preserve the naturally narrow outline and remove damaged branches as needed. In areas where powdery mildew is common, maintain good air movement and monitor the foliage during summer.