When I saw Warren Rohrer’s lovely abstract paintings in two separate exhibitions last week, I remembered Gerard Manley Hopkins’ poem, "Pied Beauty," which celebrates dappled, stippled, freckled things. I thought of the lines that praise "Landscape plotted and pieced -- fold, fallow, and plough." Rohrer (1927-1995) was an artist with a deep connection to the land. Raised on a farm in Lancaster County by Mennonite parents, he didn’t continue the farming tradition that had been in his family for generations, deciding instead to pursue painting and education. Rohrer was a gifted educator and taught for decades at the Philadelphia Museum of Art and University of the Arts. He and his wife and two sons lived in rural Lancaster County. In1984 he moved to the former studio of Violet Oakley in Mount Airy, still traveling to rural Pennsylvania to paint studies and draw.

Rohrer's early work consisted of traditional landscape and still-life painting. The show at Locks focuses on "the breakthrough period," from 1968 to 1972, where he began to work with the landscape with greater originality. Many of the increasingly abstract paintings seem to have weather in them. Poppy Garden (1969), one of the most flamboyant paintings in either show, is bubbling with sunshine and enthusiasm for life. It's full of undulating colors and textures: tiny areas of pink, orange, chartreuse and lemon yellow are balanced by wider expanses of tan, gray and soft green. Farm: April One (1971) gives the impression of a damp spring day. A broad band of chartreuse lies on the bottom and above it are smaller areas of tan, gray and minty green and tiny bits of dull purple and cherry-blossom pink.

In many of these paintings the landscape is flattened into map-like forms, with the colors of nature simplified, separated, brightened and subdued. In Crawling Landscape (1971), Rohrer seems to have raised a landscape made of dense quilted sections of green, pink, brown and violet up on an angle, suggesting a view from a high hill. Another piece, Pahaquarry West (1972), employs the systematic mark-making that would later become a primary interest. The painting suggests the landscape -- luminous peaks, shadows, dark hills and clouds -- but confirms Rohrer's decisive involvement with abstract form. Also in 1972, Rohrer made the decision to work only with a square format in three standard sizes.

The show at the PMA begins where the Locks show leaves off, with paintings made with a more systematic process that suggest the landscape more indirectly. Suddenly Rohrer's work began to synthesize the essence of his heritage -- employing crucial elements of the crafts of both agriculture and quilt making. Quilt making was an important art form in Mennonite culture, but it wasn't until Rohrer saw the "Abstract Design in American Quilts" show at the Whitney in 1971 that it began to directly inform his work. His paintings from this period have richly tactile surfaces with suggestions of rows of stitching and worn areas of fabric. Atmosphere II (1974), for example, has a pink-layered ground with thin, dotted horizontal stripes like hand stitching. These paintings are mellow, pale and meditative, and seem to emit a soft glow. Rohrer began to leave their edges less finished to reflect the process of their making.

Throughout his career, Rohrer was interested in developments in the contemporary art world, especially the methodical mark-making of Agnes Martin. In his work from the late '70s and '80s, he began to manipulate the relationships between layers of marks with greater sensitivity. For instance in Deluge (1983) he covers lower layers of gray-violet with blood red and dull green calligraphic marks with wavy patterns in dry white brushstrokes, producing a kind of moiré pattern. The ground of the painting seems to fade, and the result is flicking colors, pure movement and radiant light. He commented, "I don't want to have my paintings called landscape any more because essentially they are not that. They're paintings that are meant to be seen on their own terms."

In the late paintings, like Field: Language 10 (1991), Rohrer allows the lower layers of calligraphic marks to burst through to the top surfaces. In the large diptych Untitled 5 (1993) the bright orange calligraphic marks glisten through an overlaid scrim of dark blue-green marks. The painting is deeply metaphysical, with the farmed, worked landscape finally dissolving into nothingness. Rohrer wrote, "I learned to think about the landscape as being a message bearer. It gave me a lot of information about the nature of forces greater than I am." Ultimately Rohrer stayed true to his roots: He spent his whole life working the land.

Through Aug. 17, Philadelphia Museum of Art, 26th St. and the Parkway, 215-763-8100.