After several spates of sizzling summer weather, many gardeners are left looking for drought tolerant alternatives to lush perennial garden plantings. The three perennials mentioned below are tough customers that thrive in a sun soaked placement. Adding to their charms, they all produce flowers over a period of months and typically evade the interest of hungry deer - certainly plants that any busy gardener should consider!
One perennial stalwart for the late summer garden is tickseed (Coreopsis). Tickseeds are in the Asteraceae family. They tend to form 1 to 2 foot mounds that are covered with daisy-like flowers. They don’t shy away from the summer heat and have the added bonus of being deer resistant. Many cultivars flower from June through September, sometimes into October, and are known for their flower power
There are a number of species of tickseed, but one of the most popular and drought tolerant species is the thread-leaf tickseed, Coreopsis verticillata. Another particular winner in the world of coreopsis is the cultivar ‘Route 66’. It is an interesting alternative to predominately yellow tickseeds. This cultivar has a red eye that bleeds into the yellow petals to produce a brilliant contrast. It is not simply contrast and color that appeal to the gardener with this cultivar; it is also one of the few tickseeds that remain upright and holds its shape well throughout the season
Another tried and true cultivar is Coreopsis verticillata ‘Crème Brulee™’. ‘Crème Brulee™’ is an improved version of the well known ‘Moonbeam’. The newer cultivar is a natural mutation that has slightly deeper butter-yellow flowers. It is still pale as yellows go; like its predecessor, it is covered in a sea of flowers. This cultivar flops in the garden and the antidote is to wait until it finishes its first major flush of flowers and then sheer it back. The foliage will fill back in to a nice round form and it will re-flower (although not as vigorously).
A final cultivar worth mentioning is a recent introduction called ‘Sienna Sunset’ and as the name suggests is a lovely burnt sienna color. ‘Crème Brulee’ is one of its parents, so it is endowed with good flowering and the butterflies love it. Its color is a refreshing change from traditional yellow. It flops in rich soil, but remains more upright in a leaner growing environment.
Coneflowers (Echinacea) are a New York area native plant and well adapted to our climate variations. They are tough plants with ornamental seed heads that attract birds and butterflies. Many of the newer cultivars make wonderful cut flowers. Once these plants are established they are drought tolerant. Deer will eat just about anything these days but often these coneflowers go untouched, so don’t be afraid to splash out with one of the newer cultivars.
Recently, the color spectrum of these understated beauties has exploded. The flowers have also taken on a new form. Some are now crimped and coiffed like poodles (in fact, one of the newer cultivars is actually named ‘Pink Poodle’). The newer introductions have strong stems as well as a good head on their shoulders. A number of these new hybrids have come from Holland from the Dutch designer and nurseryman, Piet Oudolf. Oudolf is rigorous in his selection process, choosing only garden-worthy plants that not only flower well but die with dignity and keep their appearance through multiple seasons.
Some of his Echinacea cultivars that are grown on the NYBG Seasonal Walk include Echinacea purpurea ‘Fatal Attraction’, ‘Green Jewel’, ‘Vintage Wine’ and ‘Virgin’. ‘Fatal Attraction’ makes an excellent cut flower with its robust black stems and vivid purple flowers while ‘Green Jewel’ is a compact cultivar that lives up to its name. These cultivars get top marks for performance.
There is also an American breeding program with dazzling results. Dan Heims from Terra Nova Nurseries has a few new introductions to whet your appetite: the bright yellow Echinacea ‘Mac 'n' Cheese’ and the bright red Echinacea ‘Tomato Soup’. In terms of coneflowers with froufrou flowers, look for Echinacea purpurea ‘Meringue’, ‘Milkshake’, ‘Pink Double Delight’ and ‘Pink Poodle’.
There are some wonderful, warm, orange coneflowers on the market. Echinacea Sundown™ (Big Sky Series) is a glorious introduction from Richard Saul’s with iridescent orange-honey blooms. Another contender is Echinacea ‘Tiki Torch’. These are not as sturdy as the old standbys but they are worth trying.
An indispensable addition to any late summer garden are the hummingbird mints (Agastache). They are magnets for butterflies and hummingbirds and generally flower from July well into October. They are heat tolerant candidates for your garden that thrive in xeric gardens with low fertility. They are in the mint family but are the well-behaved cousin that doesn’t run all over the place. With fragrant foliage, they are deer and rabbit resistant.
Some cultivars to consider include
If you research the hardiness of these particular plants you will find that the information varies. Sometimes they are listed as tender perennials and other times the grower will claim that they survive in zone 6 or even zone 5. If you would like to grow them as perennials in the New York City area, make sure that you provide them with well-drained soil, give them a well-protected or sheltered site and refrain from cutting them back in the fall (this will give them added protection and prevents moisture from getting down into the crown of the plant).
Taylor's Guide to Growing North America's Favorite Plants by 
Native Plants of the Northeast by 
The Perennial Gardener's Design Primer by 
