Pinus johannis is a small to medium-size tree, often just a shrub, reaching 4–10 metres (13–33 ft) tall and with a trunk diameter of up to 50 cm (20 in).

The leaves ('needles') are in mixed fascicles of three and four, slender, 3–6 cm (1+1⁄4–2+1⁄4 in) long, and deep green to blue-green, with stomata confined to a bright white band on the inner surfaces.

Pinus johannis is nearly dioecious: nearly all individuals produce either male or female cones only, and trees do not appear to change their sex expression over time.

As Robert-Passini and Bailey & Hawksworth were working in different areas at about the same time, it was raised to species rank twice, first as Pinus johannis by Robert-Passini (naming it after her husband Jean) examining specimens in the Sierra Madre Oriental in Mexico, and then later as Pinus discolor by Bailey & Hawksworth examining specimens in the northern Sierra Madre Occidental in Arizona.

The white-glaucous inner surfaces of the needles make it a very attractive small tree, suitable for parks and large gardens.