How many years before new low-grow sumac will change color in the fall?
Belknap County New Hampshire
Your sumac should change color from the beginning. Some information that you may find helpful is below, which has been pulled from the Cornell publication for which I have included the link.
Rhus aromatica ‘Gro-low’ Common name: ‘Gro-low’ fragrant sumac Family: Anacardiaceae Origin/nativity: Selected from species native to most of eastern North America. Cold hardiness: Zone 3 Exposure: Full sun to part shade. Soil/cultural tolerances: Extremely adaptable, and although reports in the literature suggest it favors acid soils, we have found it to grow wonderfully in disturbed urban soils with a pH as high as 8.4. Prefers full sun but can remain dense and vigorous in partial shade. Performs well in loamy and sandy soils and is very drought tolerant, but does not fare as well in heavy clay soils with poor drainage. Growth rate: Incredibly vigorous, exceeding 2 to 3 feet per year even on older plants. A mass planting of this groundcover in a median strip in Ithaca grows over the curb and into the street and is pruned continually by car tires. Size: 3 feet tall by 6 feet or more wide in only two growing seasons from rooted cuttings. Transplant type/spacing: 2-inch pot rooted cuttings at spacing of up to 3 feet on center. Spreading method: Prodigious tip-layering and suckering. Suspected to be allelopathic. (Roots may exude compounds that inhibit germination of and/or are toxic to other plants.) Ornamental characteristics: Yellow catkins on male plants and small yellow panicles on female plants in early to mid-spring. At its best in fall with bright red color developing very late, after most other deciduous plants have finished their show. Leaf emergence in spring is also late. Wait until at least early summer until you decide whether it is dead or not. Chances are you cannot kill this plant anyway. Here is the link: http://www.hort.cornell.edu/uhi/outreach/pdfs/dwgc.pdf. I hope this helps.