"Needle-like, occurs in clusters of two; dark green; 4" to 6"; breaks cleanly when bent." -Minnesota DNR
"The initiation of cambial growth at the beginning of the growing season is tightly linked to the production of auxin in needles and shoots as they emerge and develop. Bud break and needle development, at least partly controlled by temperature patterns, typically occur in the first two weeks of May followed by cambial activity initiated by auxin production about 10 days later." -Kipfmueller, Montpellier, Trumper, & Griffin (Feb 2022), "Intra-annual Ring Width and Climate Response of Red Pine in Itasca State Park in North-central Minnesota"
For more information see https://www.dnr.state.mn.us/trees/red-pine.html and/or https://doi.org/10.1139/cjfr-2021-0210