Caleb Melchior has extensive experience with growing perennials after working at a specialty perennial nursery, Sugar Creek Gardens, in Kirkwood, Missouri. He is currently studying for a master’s degree in landscape architecture at Kansas State University.

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Green Gap Perennials
by Caleb Melchior       #Perennials

Meadow rue (Thalictrum x ‘Splendide’) looks dainty but actually grows well in difficult positions,
especially soggy garden beds.

Midwestern gardeners have a narrow gap between the cold of winter and heat of summer. But, because of the fickleness of spring weather, there is often a significant gap between the peak of spring bloom (bulbs, roses and early perennials) and the maturity of summer flowers (annuals and summer perennials, such as echinaceas and daylilies). This gap usually becomes apparent throughout late May and early June, when many people’s gardens are green and growing, but with few flowers. During this time, the temperatures are in a comfortable range for gardening, but nothing’s blooming in many Midwestern gardens. Fortunately, there are some easy-to-grow perennials that can help your garden maintain color throughout this green gap.

Cherry bellflower (Campanula punctata ‘Cherry Bells’) is a great understory plant for growing beneath shrubs and adding another layer of color to garden beds.

Perennial foxglove (Digitalis grandiflora) is more subtly colored and easier to grow than biennial varieties.

False betony (Stachys officinalis) flowers heavily throughout late spring and will rebloom in summer if cut back after the first flush of bloom.

I’ve always been amazed by the cherry bellflower (Campanula punctata ‘Cherry Bells’, USDA Zones 5 to 7). In a genus of blue and purple flowers, this one is a maverick. Its large (2 to 3 inch) flowers are soft pink with heavy mauve spotting. The spots are most dense along the veins and at the heart of the flower, creating the impression of dark stripes down the center of each petal. The soft tones of ‘Cherry Bells’ look their best in a partially shaded situation. Bright afternoon fades its color and scorches its foliage. Overall, the plant is a moderate spreader, to 18 inches high and 30 inches wide. It grows best in soils that are moist but not soggy. Rabbits will browse on bellflower foliage, but deer generally leave them alone. Their flowers are highly attractive to butterflies and hummingbirds.

Like the cherry bellflower, golden perennial foxglove (Digitalis grandiflora, USDA Zones 3 to 8) challenges preconceptions of its genus. It is subtler than the more common biennial species, with spires of soft gold and green flowers. In the species form, flower spikes reach heights of 24 to 30 inches. ‘Carillion’ is a dwarf form that rarely reaches more than 18 inches. Perennial foxglove will stop blooming when the nighttime temperatures are regularly above 80 F, but it often reblooms in fall. In cool climates, it will bloom throughout the summer. Perennial foxglove tolerates full sun, but the flowers last longest with some afternoon shade. A filtered light situation will emphasize its subtle coloration. Perennial foxglove grows best in a moist but not wet soil, in which case it will self-sow lightly. Foxgloves contain alkaloids, which are toxic to humans if eaten, so avoid planting them in edible gardens. The alkaloids in their foliage protect them from rabbits, deer and other browsers. Like many tubular flowers, foxgloves attract hummingbirds.

False betony (Stachys officinalis, USDA Zones 4 to 8) produces masses of vibrant lavender-pink flower heads on a full, but compact plant. It has frequently been planted in European gardens and is becoming popular throughout the United States for its bright color and heavy flowering. ‘Hummelo’ is a selection chosen for stronger color, with more of a purple tint than the standard species. For lighter color, try ‘Pink Cotton Candy’, a selection with pastel pink blooms. All of the false betonies grow approximately 18 to 24 inches high and 30 inches wide. They bloom heavily in full sun and should be sheared back after flowering to promote rebloom. The full habit of false betonies makes them excellent companions for roses, as they bring in color and help hide the leggy stems which ruin many rose gardens. False betonies will flower most heavily in rich soils with moderate moisture. Because their foliage is bumpy and rough, rabbits and deer avoid them. Their nectar-rich flowers attract bees, butterflies and occasionally hummingbirds.

Among the many new perennials recently being adopted in American gardens, ‘Splendide’ meadow rue (Thalictrum x ‘Splendide’, USDA Zones 3 to 8) is one of the most spectacular. Plants in our damp garden at the nursery reached 7 feet tall, with hundreds of light pink flowers on wiry stems. Each flower is only ¼ inch across, with five lavender petals around a puff of tiny gold stamens, but a single plant produces hundreds of blooms. Unlike many meadow rues, whose flowers last for only a few days, ‘Splendide’ puts on a flower show that can last for more than a month. The delicate sea-green foliage of ‘Splendide’ makes the plant an asset even when flowering is done. Because of its light, airy habit, plant this meadow rue near shrubs that will support it as flowers age and stalks become heavier. Otherwise, some staking may be necessary. Meadow rue grows best in damp, even soggy conditions. With enough water, meadow rue will tolerate full sun, but likes afternoon shade. It’s fantastic in rain gardens or for adding a bit of spectacle amongst shrubs that have already finished blooming. Deer tend to avoid meadow rue and our resident rabbit population hasn’t bothered the ones growing in our garden at the nursery. Meadow rue is somewhat attractive to butterflies.

Midwestern gardeners are continually battling winter cold and summer heat. Cherry bellflower, perennial foxglove, false betony and ‘Splendide’ meadow rue bloom in the short window of opportunity between extremes. Rather than stumbling through a green gap between spring and summer flowers, plant these four perennials and transform your garden into a constant pageant of ever-changing bloom.


Posted: 05/07/12   RSS | Print


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