Spring dreamin' this holiday season? If you're thinking about spring gardens, Cornell researchers have taken a lot of the guesswork out of pairing perennials and spring-flowering bulbs. They've conducted trials of dozens of pairings over four years to evaluate how such plantings can complement one another.

Their winning pairings, available online and described in Lawn and Landscape Magazine (December 2010), take into account not only how colorful spring bulb flowers can complement emerging perennial foliage, for example, but also how maturing foliage can mask the fading leaves of post-bloom bulbs. They considered how early bulbs can extend a garden's bloom season, how leaf texture could be used as a design element, and the role of color in combinations. They also considered the size of plants and spacing, and looked at tulips, narcissi, crocuses and daffodils in detail.

"The idea of pairing bulbs and perennials to achieve multiple goals is so desirable," said William B. Miller, professor of horticulture at Cornell and director of Cornell's Flower Bulb Research Program. "We felt it deserved more than an anecdotal approach. We created an objective study to document what works and what doesn't in a typical spring garden."

The researchers came up with more than 40 successful combinations, which includes 15 "featured" combinations, such as pairing the daffodil "Salome" with the phlox "Bill Baker." Says the website: "This combination illustrates the use of bulbs with perennials to extend the bloom season. After the narcissus are finished, the phlox explodes with blooms, masking the bulb foliage. This combo would work with many narcissus and probably also with early tulips."

Other winning combos include pairing the tulip "Don Quichotte" with the geranium "Claridge Druce," for example, and the April-blooming hyacinth "Jan Bos" with the dark-leafed, summer-flowering perennial penstemon "husker red."

If the ground is not yet frozen, it's not too late to plant bulbs, says Miller. Perennials, on the other hand, can be planted throughout the spring as well as into the summer and fall.

Funding for the research came from Anthos, the royal Dutch trade association for nursery stock and flower bulbs in the Netherlands.