Compelling combos

Top: Tulipa ‘Queen of Night’ and Sedum ‘Matrona'; Middle left: ‘Fortissimo’ is aptly named: its enormous, handsome two-tone yellow and orange blossoms surely shout in the mid-spring garden; Middle right, top: Narcissus ‘Fortissimo’ and Papaver orientale ‘Turkenlouise’; Middle right, bottom: Pulsatilla vulgaris ‘Papageno’—Commonly called pasque flower by some, this is a low-growing spring bloomer with bright flowers and unusual fern-like cut leaf foliage rather like a carrot’s, but hairy. Bottom: 'Queen of Night,’ christened in 1944, is still considered top contender for the title of “blackest” tulip (though its color is actually a very dark, deep velvety maroon).
Garden retailers and landscape designers know that perennials and spring-flowering bulbs make great companion plantings. Not only can the proper pairings look great together, they can be mutually supportive. Colorful spring bulbs can complement emerging perennial foliage. When that foliage matures, it can mask fading leaves of post-bloom bulbs.

For the most part, savvy gardeners have relied on a practiced eye and experience to create combinations that spark spring magic. Now researchers at Cornell University have cast the objective eye of science on the topic. In a series of trials covering four seasons at the university’s Ithaca, N.Y., trial grounds (USDA zone 5), the Cornell team put various pairings of bulbs and perennials to the test. Their results are now available on the university’s website at www.hort.cornell.edu/combos. Cornell professor William B. Miller, who is director of the university’s Flower Bulb Research Program, led the Cornell team.

“The idea of pairing bulbs and perennials to achieve multiple goals is so desirable that we felt it deserved more than an anecdotal approach,” Miller said. “We created an objective study to document what works and what doesn’t in a typical spring garden.”

The combination trials were designed to achieve four goals:

1. Look at how early bulbs help extend the garden’s bloom season.
2. Explore how perennials might best be used to mask the dying foliage of post-bloom bulbs.
3. Consider leaf texture as a design element.
4. Examine the various roles color plays in creating combinations.

The Cornell scientists evaluated the plantings for their overall performance and benefits, and did not necessarily look for combinations that bloomed simultaneously. They focused on combinations that worked. Following are 15 of their top performing combos.

Allium karataviense ‘Ivory Queen’ with Aster macrophyllus. The allium leaves match the aster foliage nearly perfectly, allowing for the blooms to show with no worry of unattractive foliage. The two plants grow at the same rate and the blooms are still visible.

Anemone blanda ‘White Splendour’ with Rheum palmatum ‘Atrosanguineum.’ The fine white flowers of the anemone contrast well with the dark, coarse foliage of the rheum. The anemone blooms before the leaves of the rheum get too large, and then the rheum grows to cover the old foliage of the anemone.

Hyacinthus ‘White Pearl’ with Rheum palmatum ‘Atrosanguineum.’ Just as the rheum contrasted with and then covered the anemone, it does so for the hyacinth. This combo could be even better if a multiflora or “looser” white hyacinth were used.

Hyacinthus ‘Jan Bos’ with Penstemon ‘Husker Red.’ The emerging penstemon leaves are dark purple just as the hyacinth is blooming, creating a nice color scheme. The penstemon is slow enough to allow the hyacinths to finish blooming and reenergize their bulbs, and then takes over before the foliage becomes unsightly.

Ipheion uniflorum ‘White Star’ with Potentilla argentea. The interesting texture of the newly emerging potentilla leaves makes a complementary surrounding for the blooming ipheion. The potentilla then grows to sufficiently cover the browning leaves of the ipheion, making a useful combination.

Narcissus ‘Fortissimo’ with Papaver orientale ‘Turkenlouis.’ An excellent functional combination whereby the narcissus flowers slightly above the developing poppy leaves. The leaf-texture contrast between the narcissus and papaver make for an interesting mix early on, and the fast growth of the papaver covers the narcissus foliage quickly.

Narcissus ‘Ice Follies’ with Pulsatilla vulgaris ‘Papageno.’  This combination shows contrasting foliage texture, simultaneous blooming that complements both plants, and perennial foliage cover after the bulbs are finished for the season.

Narcissus ‘Pink Charm’ with Cimicifuga ramosa ‘Brunette.’  The foliage of the cimicifuga complements the narcissus foliage and flowers early in the season. It also grows large enough to mask the browning daffodil leaves. This combo would be especially excellent if narcissus were interspersed more evenly.

Narcissus ‘Salome’ with Phlox paniculata ‘Bill Baker.’  This combination illustrates the use of bulbs with perennials to extend the bloom season. After the narcissi are finished, the phlox explodes with blooms, masking the bulb foliage.

Narcissus ‘Slim Whitman’ with Achillea filipendulina ‘Gold Palette.’ The leaf texture of the emerging achillea offers contrasting texture, adding to the interest of the spring garden. The achillea foliage grows tall and thick enough to hide the fading narcissus foliage.

Tulipa 'Ballade' with Geranium ‘Mayflower.’ The height of the purple-hued tulip at bloom and the early geranium foliage makes the tulip blooms look as if they are floating in a sea of green. Later, the geranium’s foliage and purple flowers mask the fading tulip leaves.

Tulipa ‘Don Quichotte’ with Geranium ‘Claridge Druce.’ The blooming of the tulip and the growth of the geranium coincide perfectly. A functional combo, with the geranium foliage working to mask the tulip leaves as they senesce. The pink color of the tulip is echoed by some purpling of the geranium, caused by cool spring weather.

Tulipa ‘Negrita’ with Stachys byzantine. This combination has it all: extension of the blooming season, contrasting and complementary leaf color and texture, and the right timing for old leaf coverage. The purple tulip is excellent with the gray stachys.

Tulipa ‘Parade’ with Dicentra spectabilis ‘Alba.’ The red blooms of the tulip with the white blooms of the dicentra add charm to the spring garden. As the tulips finish their show, the dicentra continues to bloom for several more weeks.

Tulipa ‘Queen of Night’ with Sedum ‘Matrona.’ The purple tulip-flowers complement the purple-edged foliage of the sedum to make a truly wonderful spring display. The deep, dark purple of the almost-black tulip flower echoes the hues of this dark-leaved sedum. The sedum then grows large enough over the season to overtake the old tulip foliage.  This combo would be effective with any upright, dark-leaved sedum.

The Cornell site also features suggested combinations of perennials with tulips, narcissi, crocuses and more. There are tips and how-to sections and even accounts of combinations the researchers found to be less than successful. For more information about the Cornell University Department of Horticulture visit www.hort.cals.cornell.edu. For more information about flower bulbs visit www.bulb.com. To visit the Cornell Bulb & Perennials Combinations website, visit www.hort.cornell.edu/combos.