Fab Late Season Annuals

My favorite selections from a year of experimentation

The wet spring and early summer has been a blessing and curse in the border this year.  Moist-loving perennials like Mondarda and Eupatorium have swelled to gigantic proportions, growing several feet higher than they've grown in the past two years. All the while, my drier-loving perennials have melted with fungus and mildew.  I've just finished ripping out several dozen fungus-covered Perovskia and Agastache ‘Black Adder’.  It’s funny, because if you asked me last year what kind of plants would be on my list of “plants of the future”—that is, climate change worthy plants--I probably would have listed those two.  But one wet season and they are gone.

I have long complained that summers in Washington, D.C. area are essentially subtropical.  While perennial gardeners in cooler climates like Maine, England, and the Netherlands enjoy spectacular bonanzas of July and August blooms, we humidity-bound gardeners watch all but the most thuggish of our perennials flop and generally poop out.  Of course, it is entirely possible to have a beautiful late season perennial garden in the mid-Atlantic; it is just hard to have both a beautiful early season and late season perennial garden here—particularly for space-challenged gardens.  Our growing season is so stretched out (with a thirty degree temperature differential); what looks good in May most definitely does not look good in August and vice versa.    

So this year, I've invested heavily in annuals and tropicals to pump up the late season border.  I can’t tell if my foray into annuals and tropical is a strategic master-stroke or a sign that I have slipped too deep into horticultural self-indulgence. Whatever my diagnosis, I've learned quite a bit this year about combining these plants in perennial garden—including quite a few missteps (such as giant Colocasias shading out half a dozen sun-loving plants).  But there have been enough happy accidents that I thought I’d share a few of the better moments.  I've seeded almost two dozen different plants this year and tried a range of different tropicals. Here are my favorites:

Tagetes patula ‘???’ (1m tall)

Tagetes 'Cinnabar' courtesy of Gardens Illustrated

A three-foot tall marigold on loose, ferny foliage?! This strain of French marigolds is a marigold that even marigold-haters would love.  I collected this seed from a friend who apparently mail ordered it from California.  Most marigolds are dumpy little bedding plants; this little lovely grows two to four feet tall on beautiful finely-cut foliage.  After years of lusting after Tagetes ‘Cinnabar’ at Great Dixter, I’m thrilled to finally have one of these loose, landscape marigolds.  Some sources say it may be a Himalayan cultivar; others say it a true French strain.  Single orange and red flowers grow on top of a plant that more closely resembles an aster in form than a marigold.  Blooms July to November and re-seeds readily.  This year, I tucked this in a few late season holes.  Next year, I will feature this annual front and center.  Annies Annuals have several varieties of this type of marigold (Villandry & one called ‘Gina’s Himalayan’). Sarah Raven features ‘Linnaeus,’ a looser variety of this marigold with deep amber colored flowers.

Tithonia ‘Feista del Sol’

image by Jule Dansereau

Several years ago I grew the straight species Tithonia rotundifolia and was delighted with the result.  The color orange of these daisy-like blooms is so pure, it almost glows. A real butterfly magnet. The only problem was that this annual grew eight-feet tall and six-feet wide—taking up much more real estate than I could stand.  But thanks to Swallowtail Garden Seeds, a compact version called ‘Fiesta del Sol’ is available that tops out about thirty inches (75cm) tall.  The best part is that this annual never sags in the heat.  Looks as good in 110 heat index afternoons as it does in late November.

Cosmos ‘Psyche’ Series

image courtesy of Berkshire Botanical Garden

After trialing many different types of Cosmos, my favorite by far is the Psyche series.  Here’s my advice: don’t select Cosmos for height or color; instead, go for bloom size.  The Psyche series has blooms 3-4 inches wide.  That’s four times the size of some of the other varieties, one of the largest of Cosmos bipinnatus species.  I’m not generally a fan of double blooms (they always look a bit over-bred), but these double blooms are frilly without being precocious. The densely ferny foliage is a real plus for this series as well--not at all leggy like some Cosmos, but instead ferny and lush  These high-spirited, vigorous cosmos evoke late summer exuberance like few other plants. Grows three to four feet tall.  Very long lasting. Swallowtail Garden Seeds.

Dahlia ‘Arabian Night’

Early color starts cherry red but deepens to almost a black

When it comes to dahlias, there are a million beauties.  But ‘Arabian Night’ is a classic—the Sophia Loren of dahlias.  The plant seduces with its velvety texture and smoldering red color.  It’s hard to describe the allure of the color.  The flowers open a dark cherry red then mature into a deep currant-color (almost black), creating the illusion of shadow even in the full sun.  The effect is flirty yet deadly. If temptation itself were a color, this would be it.  Grows 36 inches tall. Brent and Becky's Bulbs.

Ensete ventricosum maurellii, Red Abyssinian Banana

Ensete maurellii next to Persicaria polymorpha in my garden. The banana has tripled in size since this photo was taken

No other banana variety compares.  Each leaf can grow four to eight feet long, making a stunning silhouette in the back of the border. The absolute best feature of this banana is the high gloss, burgundy foliage of the stems and undersides of the leaves.  Something about this color that blends incredibly well with grasses and other blooming perennials.  Red Abyssinian Banana has one of the best silhouettes of any of the banana selections, much more compact and dense than many of the Musa genus which eventually look like palm trees.  This is one of the more pleasurable plants I've ever grown.  Too bad it won’t survive the winter. Plant Delights Nursery.