Perennials for Heat-Baked Gardens

This is the first summer of my retirement from teaching, the first summer I can spend every day from early spring to first frost and beyond in the garden.  There is time to expand our vegetable and small fruits garden with new raised beds, a project that requires resetting of posts for the deer fence, and time to focus mind and camera on the diversity of insect life in Marjorie’s Garden.  And there is time to visit other gardens, both public and private, for discovery of new plants and new ways to garden

This past week, Marjorie and I decided on the spur of a moment to spend a hot summer day at Coastal Maine Botanical Gardens (CMBG) in Boothbay, Maine.  Subtracting the five hours of travel time to and from Boothbay and an hour for a meal at Moody’s Diner in Waldoboro on the way home, we had about four hours to stroll through the Gardens, all of it in the glaring sun.  We discovered several annuals and perennials that thrive in gardens baked by the summer heat, some varieties new to us and others old friends, all grown to perfection and displayed in striking combinations.  We left the Gardens with a long list of plants for the empty sunny spots in next year’s garden, a few of which are described below.

Tiger Eyes and Sweetfern

'Tiger Eyes' is a cultivar of the native staghorn sumac.  It grows to only 6 feet tall with golden yellow foliage and less suckering than the species.

‘Tiger Eyes’ is a cultivar of the native staghorn sumac. It grows to only 6 feet tall with golden yellow foliage and less suckering than the species.

At one spot along the walkway through the Gardens we were greeted by a six-foot-tall tree stump with two holes recently excavated by a pileated woodpecker.  My eye then quickly moved down slope to the golden yellow leaves of Rhus typhina ‘Tiger Eyes’, a cultivar of our native staghorn sumac.  Many gardeners would have removed the stump, but it works in this scene to create an interesting contrast between two worlds, natural and cultivated, while bringing these worlds closer together.

‘Tiger Eyes’ is considered a better landscape plant than the species because of its dwarf size, rarely exceeding six feet tall and wide, and minimal suckering.  The pinnately-compound leaves emerge chartreuse in spring, quickly mature to bright yellow, an may acquire orange and scarlet tones in autumn.

‘Tiger Eyes‘ has been around a while, discovered in a nursery garden in 1985.  I grew it in my garden in Orono over a decade ago and have seen it since whenever I visit Berkshire Botanical Garden.  For the most part, it seems to belong to the realm of botanical gardens rather than private gardens.

Sweet fern makes an attractive informal hedge in full sun.

Sweet fern makes an attractive informal hedge in full sun.

Along the curve of a stone walkway, the native sweet fern, Comptonia peregrina, had been planted as an informal hedge.  In the wild, I often see this low shrub thriving in dry heat-baked soils, as it does along the lane where Mia the Beagle and I take our daily walks.  As I walked along the planting at CMBG, I couldn’t resist rubbing a few leaves between my hands, releasing the spicy aroma unique to this plant and responsible for its name.



Herbaceous Perennials that Take the Heat

Echinacea 'Hot Papaya' (foreground) combined with Penstemon digitalis 'Husker Red'.

Echinacea ‘Hot Papaya’ (foreground) combined with Penstemon digitalis ‘Husker Red’.

One of my favorite plantings at CMBG this year consists of a long swath of white-flowering ‘Husker Red’ penstemon (Penstemon digitalis ‘Husker Red’), a cultivar named for its red stems and one that is highly favored by bumble bees.  At CMBG, it grows in front of the bright orange flowers of Echinacea purpurea ‘Hot Papaya’.  Backed by a line of ornamental grasses (pennisetums, perhaps), the entire scene spoke to me of wildflower meadows.  From our own experience with ‘Husker Red’ and coneflowers other than ‘Hot Papaya’, we know both of these perennials as favorites of bees and butterflies.

Coreopsis 'Mercury Rising' grows in front of a bright red annual coleus.

Coreopsis ‘Mercury Rising’ grows in front of a bright red annual coleus.

In another full sun bed at CMBG, deep red coleus grow behind a swath of Coreopsis rosea ‘Mercury Rising’, a Zone 5 tickseed with wine-red blossoms, each with a golden orange button in the center.  This is a must-have perennial for hot summer gardens.  Even the back of each petal is colorful, creamy yellow with a purple stripe.

Relief from these hot colors comes in the form of Eryngium planum ‘Blue Glitter’, a clump-forming sea holly that produces steel-blue flower heads through the summer.  The individual flowers, each tiny and stemless, are packed into egg-shaped heads that resemble those of thistles.

Eryngium 'Blue Glitter'' is a favorite of bumble bees.

Eryngium ‘Blue Glitter” is a favorite of bumble bees.

Below each flower head is a narrow, spiky collar of spiny blue-green bracts.  Overall plant height ranges from 36 to 40 inches.  ‘Blue Glitter‘ is easily grown in dry sandy soils in full sun.  Grown in overly fertile soils or even a little shade, the tall plants may sprawl.  Choose the site carefully, for these taprooted plants transplant poorly.

In Marjorie’s Garden, from spring through early summer, nodding onion’s (Allium cernuum) delicate clusters of lilac-pink bell-shaped flowers nod over soft, flat, arching leaves that persist into late summer.  At CMBG, the flower color of this ornamental onion is displayed beautifully

Nodding onion, Allium cernuum, growing in front of catmint, Nepeta faassenii 'Blue Wonder'.

Nodding onion, Allium cernuum, growing in front of catmint, Nepeta faassenii ‘Blue Wonder’.

against the dark blue blossoms of a hybrid catmint, Nepeta x faassenii ‘Blue Wonder’.  We have this same catnip in the garden, at the moment interplanted with lady’s mantle.  While the nepeta’s dark blue blossoms and lady mantle’s chartreuse flowers make an interesting combination, Marjorie is already talking about bringing the nepeta and allium closer together for next year.

We returned home from our day trip tired and sunburned, yet inspired.  Such garden visits are necessary, I think, as they are part of our continuing education as gardeners, expanding our perceptions of the possible, infusing us with enthusiasm.

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About Reeser Manley

I was born in Laramie Wyoming but moved to the southeast at an early age. I was educated through my B.S. in Biology in the Columbus, Georgia area, then crossed the Chattahoochee River to earn my M.S. in Botany at Auburn University. For the next ten years, I worked as Horticultural Manager for the George W. Park Seed Co. in Greenwood, S.C. At 40 years of age, I decided to return to graduate school and in 1994, I earned a Ph.D. in Horticultural Science from Washington State University, Pullman, Washington. Fast forward through 10 years at university (7 at UMaine, Orono) and you find me teaching high school science in Eastport, Maine, the edge of the world, and writing a weekly garden column for the Bangor Daily News. My new book, The New England Gardener's Year, a Month-by-Month Guide for Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, Connecticut, and Upstate New York”, will be published later this year by Cadent Publishing. You can learn more about the book by visiting its Facebook page: