Richard Mayhew may be the greatest contemporary artist you've never heard of. He's been called a romantic painter, an abstract expressionist and an American impressionist; none of the labels fit. Abstract landscape artist begins to approach a description of the Santa Cruz-based painter's work, but it doesn't complete the picture; his mystical scenes of trees, valleys and mountains, executed in a jazzy, improvisatory style, are of no known landscape other than one firmly rooted in Mayhew's state of mind, expressing, as he once said, "a universal space with the illusion of time."

During his ongoing 40-year career, Mayhew, 84, has painted the woodlands of Pennsylvania, the creeks and meadows of North Carolina, glimmering ponds of New England, and, more recently, the luminous, shout-it-out golden light of California, but his paintings are informed less by a defined sense of place than by memory and spirit – poems in painterly form. For Mayhew, landscape is the language of freedom and emotion.

The Art of Richard Mayhew, an exhibition of works from the 1950s to the present, on view at the Museum of the African Diaspora through January 10, 2010, is one of three concurrent shows that, taken together, form a welcome, long-overdue retrospective of an artist who is not as well-known as he deserves to be. The de Saisset Museum at Santa Clara University focuses on Mayhew's mid-career from 1975 onward, while the Museum of Art and History in Santa Cruz showcases work produced since he moved to the surfer haven in 2000.

Of African American and Native American descent, Mayhew, whose father was a house painter, grew up in Amityville, New York. In summer, the picturesque coastal town on Long Island was a mecca for artists, one of whom, a medical illustrator, became his mentor. In 1951, Mayhew enrolled at the Brooklyn Museum, which would give him his first solo show four years later, and studied with impressionist Edwin Dickman, Hans Hofmann and German expressionist Max Beckman. American in approach, Mayhew both broke with and reinvented the Hudson River School, and came into his own in the swirl of the 1950s New York art scene, an environment inhospitable to landscape.

Thematically, Mayhew is partial to a large solitary tree or a group of trees at the center of a canvas, but subject matter is secondary. Make no mistake: Mayhew is all about color: bold, explosive, volcanic color that, in later works, trend toward the psychedelic. The ferocity of his colors doesn't seem to match the demure man depicted in "Self-Portrait, 1978," a serious guy with a mustache, wearing a blue shirt, or the mellow fellow messing around with paints in the studio.

The derivative, less interesting early pieces such as "Thicket, 1962," with their muddy greens, murky umbers and dark, impenetrable clusters of trees huddled like refugees on damp embankments at dawn, recall the Romantics and Constable, but when his colors turn toward softly etched, lustrous cobalt blues and greens as in "Twilight," Monet springs to mind. Then, as if he had been plugged into an electric socket, originality arrives in a wonderland of purple trees with screaming scarlet or rich magenta crowns set against melon-hued skies. In "Ritual, 2007," a mass of brilliant fuchsia trees occupies the background, and a lake of glacier blue lays serenely in the middle distance; a tree is hit by a blast of morning light that makes the scarlet so bright it hurts the eyes in "Love Bush"; rich purples dominate "Rhapsody, 2002," complementing periwinkle blue shapes flanked by an overgrown field.

Given that Mayhew is far from a household name, it's disappointing that MoAD offers scant supporting material or background information. Minimally explanatory labels for a few select paintings do little to illuminate, but a catalogue is promised, and an informative 28-minute video loop playing in an adjoining gallery provides much-needed context. It reveals a gentle-mannered, elegant artist at work in his studio, dampening paper, letting colors bleed into each other, and spraying water to blunt boundaries, a process that produces the undulating colors that characterize his paintings.

Moving back and forth between watercolors, oils and pastels, Mayhew, a former jazz singer, merges jazz with painting as fluidly as he merges colors on the canvas. It's best to turn off the brain and experience the show as an immersion in a bath of sublime color, accompanied by a jazz-infused soundtrack.

Information: (415) 358-7200 or www.moadsf.org.