Beauty is best when chanced upon, glimpsed like a ravishing girl skipping down a subway stairs, or flickering in the rainbow hues of a leaping trout.

It's not something to expect even when strolling through an art museum, where most beauty is formal, fixed and labeled to tell a story. Sure, there's beauty afoot in museums, but not often of the startling, unexpected sort.

And so on a recent afternoon, several visitors at the Minneapolis Institute of Arts seemed a bit shocked when they wandered into the gallery where Margaret Wall-Romana's paintings are on view through April 3 in "Painting Before and After Words." A couple straightened, stared and moved in closer. Another struck up an awed conversation with a stranger. Having stumbled onto something strangely fresh and unexpected, they seemed compelled to share their amazement. Beauty had caught them unawares.

To call Minnesota artist Wall-Romana a painter of visionary botanical art is too clinical for her results, and too modest for her aspirations. She is a painter of exquisitely detailed flowers and vines, leaves and grasses, with an occasional fallen feather or crumpled bird woven into blowsy bouquets of roots and twigs that seem to drift through space. Sheer veils of soft color -- apricot, creamy ivory, ice blue -- flutter behind her blossoms and sometimes frame distant vistas of low mountains, mossy meadows, limpid seas. Her blooms and greenery are familiar things: dandelion leaves and clover blossoms, cascades of wild rose petals and prickly leaves, translucent white daffodils whose orange trumpets are shadowed in chartreuse.

Their bounty soars and floats, untethered from the earth yet bound up in the life cycle of living things. The lovely streaky-pink coneflower heads in "Towards & Away" are off-center and tangled in a knot of bruised claret pigment, broken stems and tattered gray feathers. Puffs of dandelion seeds dangle from vines swooping improbably above a flowery bog in "Memento Lucem." Working in a stylistic fusion of abstraction and illustrative detail, she everywhere commingles earth and air, renewal and decay, life and death.

This is deeply romantic painting of a sort seldom seen in contemporary art except in greeting-card clichés, and it is therefore dangerous turf for a painter with the serious pretensions of Wall-Romana. One misstep with those luscious backdrops, those luminous clouds, those fluttering petals and she'll be damned to Hallmark heaven. But she never falters and is saved by the sheer virtuosity of her painting.

Unfolding on curiously shaped canvases up to 11 feet long and 6 feet high, her images have a grand scale reminiscent of the Hudson River School landscapes of the 1850s that found god in the grandeur of the American wilderness. Her paintings have been compared to the country fetes of Fragonard and the airy frescoes of Tiepolo -- 18th-century painters whose pastel palette she embraces -- but more likely her compositions are indebted to the innovative botanicals of Martin Johnson Heade , a 19th-century American who placed orchids and hummingbirds in the foreground of moody, moonlit landscapes.

She, however, claims to have been inspired by Rogier van der Weyden , the medieval Flemish master of deeply moving Christian imagery. In a direct tribute to the pious Van der Weyden, she symbolically replaces the crucifix in his famous "Descent From the Cross" with a dandelion in a landscape-halo above a scrum of decaying vegetation. That one is too labored and a tad too moralizing. But still, her work is breathtaking and a worthy companion to the Venetian paintings that are the institute's marquee show this spring.