Cool it Down with Summer Whites

Yes, Gentle Readers, it's been a very hot summer with record temperatures and less than average rainfall, coming on the heels of an almost snowless winter. Ground water is depleted and gardeners as well as plants are feeling stressed, tired and wilted. But we soldier on, resilient and ever hopeful... that's part of what it means to be a gardener!

Like a crisp linen shirt, white in the garden can be a refreshing and revitalizing antidote to the sultry weather. There are many choices with either flowers or foliage in shades of white to help alleviate the heat, at least visually. Here, a few of my recommendations...

The Bottlebrush Buckeye, Aesculus parviflora, is one of our most magnificent native American shrubs. Grows 6-12 feet tall and forms a colony of stems in time, but never invasive. Best in rich soil and part shade, it seldom needs pruning and and is almost never troubled by pests or diseases.

The panicles of tubular white blossom attract butterflies when they appear in July, and the handsome palmate foliage turns buttery yellow in fall. Its native range is the southeast US but it's perfectly hardy all through USDA Zone 5. Underappreciated, but highly recommended.

Oh those botanists! I still keep calling this Cimicifuga racemosa, but it's now Actaea racemosa. Nonetheless, one of the best late-blooming perennials for shade, and a native as well. Curvaceous spires of fluffy white flowers soar as high as seven feet on strong slender stems, carried well above the mounds of ferny deep green foliage. Needs at least average moisture to thrive but really at its best in an area that never dries out.

This is a plant with some fascinating common names: Bugbane, Snakeroot, Black Cohosh, based on medicinal and insecticidal qualities of the rhizomes and their reptilian appearance. I just think it's a wonderful architectural perennial that's valuable for blooming so late in the season. In addition to the plain green species, there are quite a few selections with darker, purplish foliage that are even more decorative.

Cornus 'Ivory Halo' is as cool in summer as it is warm in winter, thanks to its clean, white-margined leaves that unfold as the bright red twigs fade with the coming of spring. The red- and yellow-twigged shrubby Dogwoods are popular for their beautiful stems that show up so nicely against the snow, but most of them inspire very little interest once they leaf out. Not so with this one, a variety of Cornus alba, the Tartarian Dogwood. Easy to grow and will mature to 6-8 ft, although it can be kept smaller with pruning, and it's advised to remove about a quarter of the stems each year to encourage new shoots, which have the best winter color. The flowers aren't much to rave about, but the fruit is very attractive to birds, and the fall color is often quite good.  

Hydrangea arborescens 'Haas Halo' is the lacecap cousin of the widely planted 'Annabelle', but I think much more elegant. The 14" wide blossoms are carried on sturdy stems 3-5 feet tall with deep green, glossy foliage, and because it's a seedling of the native Smooth Hydrangea, its refined appearance is backed up by a very tough constitution. Makes a stunning mass planting or a beautiful specimen, and the flowers are popular with honeybees and other pollinators. They also dry well, or if left on the plant through the winter,  look wonderful dusted with snow.

One of the longest blooming perennials, Calamint (Calamintha nepeta ssp. nepeta) is the perfect choice to face down taller plants at the edge of a border, or lovely used in mass on its own. Low bushy clumps--not invasive like the true Mints--flower from June until September with clouds of tiny, white or ice-blue blossoms adored by honeybees. The foliage is delicate and extremely fragrant when crushed or even brushed against, adding to its cooling properties. A real workhorse in the landscape with a lot of airy charm to boot.

Miscanthus sinensis 'Cosmopolitan' is one of several white-variegated Maiden Grasses on the market ('Cabaret' and 'Variegatus' are also good choices). Tall and stately with beautiful arching foliage edged in creamy white, 'Cosmopolitan' looks great with large scale perennials and can hold its own as a contrast and complement to shrubs. Like all grasses it adds movement to any planting, and will fade to shades of golden tan and look good well into winter. Needs adequate moisture to establish but otherwise trouble free... just be sure to cut it down early in spring so the sun can warm the roots and encourage strong new growth.

Early summer is the flowering time for Viburnum plicatum 'Shasta', but it looks wonderful all season long and is so useful as a large screen I couldn't help including it in this list. Lacy flowers carried on elegantly layered branches are followed by small fruit that Robins love and clean foliage that turns shades of russet in fall. Best with reliable moisture, but will thrive in average soil as well, in sun or shade. A great, dependable shrub that can block out an unsightly neighbor in just a few seasons!

Liatris spicata is commonly seen in purple, but 'Floristan White' is a variety I've come to love. This native's fluffy wands open from the top down, while most flowering spikes open from the bottom up, and it increases reliably every year, forming something like a corm at the base of the stems that can be easily divided to increase your stock. The spikes turn a pleasing shade of tan and remain decorative through the winter. Versatile Liatris looks equally at home clumped in a traditional flower border or scattered throughout a grassy meadow planting.

Border Phlox (Phlox paniculata varieties) have been around since Victorian days and although they're sometimes martyrs to mildew and viruses, I'd find it hard to garden without them. No other summer perennial has quite the visual impact, or the delicious fragrance, especially notable in the white varieties. 'David' and 'Volcano White' (above) are two cultivars I grow, and both have improved disease resistance. One key to success is to keep them consistently moist, easier said than done in a summer like this one, but well worth the effort!

Oakleaf Hydrangea, Hydrangea quercifolia, is one of the crown jewels of American native shrubs. Easy to grow with beautiful foliage, gorgeous flower panicles, spectacular fall color and interesting exfoliating bark, this is truly a four-season plant. Its only drawback is that deer absolutely maul it in the winter, so site accordingly, net it, or spray and pray.

How can you resist this fall color?

One of my favorite native perennials, Eryngium yuccifolium grows roadside in the Louisiana pinelands where I grew up. The greenish-white bobble flowers are carried in branched clusters on tall stems above jagged grassy foliage that forms handsome clumps about the size of a Daylily plant. The folk name of this plant is "Rattlesnake Master", a reference to its supposed ability to cure snakebite. I'm happy just to grow it for its interesting texture and decorative winter seed heads! Perfectly hardy in the Hudson Valley given good drainage and full sun.

Another terrific native perennial is Culver's Root, Veronicastrum virginicum. Its tall, elegant habit lends needed verticality to perennial borders, but it looks fantastic in a meadow planting as well. Easy to grow, low maintenance, adaptable to most soils from average to wet, and attractive to butterflies and other pollinators. There are lavender cultivars on the market but I think their color is a bit washed-out, so I much prefer the clean white one. Blooms July into August, above pretty whorled foliage, and the spent flowers look interesting all through fall and winter, so no need to deadhead.

The White Turtlehead, Chelone glabra, is a lesser-known native perennial but one you might spot in low wet areas or even roadside ditches anywhere in the Hudson Valley. The common name comes from the unusual shape of the flowers, said to resemble a turtle's head, and the genus name is derived from the Greek chelone, meaning tortoise. Beautiful in a bog garden or at the margin of a stream or pond, where it can get the regular moisture it needs. Otherwise trouble-free, cool and lovely in late summer.

Summersweet is the common name for Clethra alnifolia, and a good name it is too, for no other American native has such a heavenly scent when in bloom. The panicles of flowers are irresistible to butterflies and honeybees, and are followed by bead-like seed heads that remain attractive into winter. Deciduous foliage that's a fresh green all summer, turning golden yellow in fall. Suckers to form colonies and happiest with damp feet and its head in the sun. There are pink-tinged varieties too, all fragrant and lovely.

The Mountain Mints, Pycnanthemum species, are enjoying quite a vogue right now among gardeners who've discovered them, and I recommend you try this one if they're new to you. It's Pycnanthemum muticum, aka Short-toothed Mountain Mint. The silvery bracts that surround the true flowers make landing pads for a whole menagerie of pollinators: butterflies, bees, moths, beneficial wasps and more. Makes a great cut flower too, lasting weeks in a vase, and the foliage smells deliciously of pennyroyal. Even though they're called "mints", there's no need to be alarmed... they are vigorous native plants but not nearly as aggressive as the culinary Mints.

A sunny spot with good drainage is the perfect home for Silver Sage, Salvia argentea. Huge furry lobed foliage like Lamb's Ear on steroids, and it blooms early in the summer with a big spike of white flowers. Not a long-lived perennial but I've had excellent results keeping it going by mulching with gravel and removing the bloom spike after flowering to prevent seed formation. A real eye-catcher in the perennial border or rock garden, and children love to pet it!

One of the big guns of late summer is the Pee Gee Hydrangea, Hydrangea paniculata 'Grandiflora', a classic shrub first introduced into cultivation around the time of the Civil War. There are now dozens of varieties, in all sizes, and sold as shrub forms or standards (above) which are often called "Tree Hydrangea", a misnomer.
All of them are beautiful, reliable shrubs for our climate, winter hardy and floriferous, only requiring decent soil, reasonable moisture and a modest pruning job every spring before they leaf out.

'Bobo' is a Hydrangea paniculata variety recently introduced from Belgium, and its compact size (under 5 ft.) makes it more manageable for many situations. Plus it's a prolific bloomer.

Almost all the paniculatas start out white and turn shades of pink as fall approaches, and 'Pink Diamond' is one of the prettiest that colors up well, and has open panicles that fit better into naturalistic settings than some denser-headed cultivars. In fact, there's a Hydrangea paniculata variety for just about every taste, from beach-ball sized heads ('Phantom') to elegant attenuated lacy sprays ('Kyushu) and everything in between.


I hope you've enjoyed my list of summer coolers... I'm sure you have some favorites of your own that I passed over. The goal is to make our gardens enjoyable, personal and inspiring, even in the most trying weather!