Louis Raymond experiments in his own gardens like

a mad scientist, searching out plants that most people have

never seen before & figuring out how to make them perform.- The Boston Globe

…Louis Raymond ensures that trees can grow in Brooklyn…

or just about any other place where concrete consumes

the dirt and skyscrapers shield the sunshine.- USA Today


NEW Trips to Take!

Myrtle's easy when the conditions are right.


NEW Plants to Try!

Louis tries to capture the exact words to describe the fleeting but deep pleasures to be found in these Summer-into-Autumn incredibles.


New Gardening to Do!

Allergic to bees? You can still have an exciting garden, full of flowers and color and wildlife.


Plant Profiles

White-flowered Hardy Ageratum



Flowers that bring champagne effervescence to your August garden:  White-flowered hardy ageratum.


The tiny, tiny little buds are in tight clusters of fifty and more—and when they decide to open, each one tosses out a long white streamer, I mean stamen, worthy of a New Year's Eve celebration.  Plenty of distraction from the purple-leaved dahlia, which is holding out for September to start into bloom.




The hardy ageratum will still be celebrating.



Here's how to grow this almost-too-easy perennial:


Latin Name

Conoclinium coelestinum 'Album'

Common Name

White-flowered Hardy Ageratum


Asteraceae, the Aster family.

What kind of plant is it?

Groundcovering perennial.


Zones 5-110.


Multi-stemmed, strongly upright, energetically outward-bound.

Rate of Growth


Size in ten years

Conoclinium can get two to three feet tall and can spread almost indefinitely.  Taller in moister and water-side locations, where spread is more vigorous, too.


The uniform height and dense growth make Conoclinium look as well as perform as an excellent groundcover.  The surprise is the Summer flowers, showy, graceful, and long-lasting.

Grown for

its vigor: Conoclinium's closely-spaced vertical stems and plentiful leaves combine to create a density of growth that is absolutely weed-proof.


its flowers: Small but profuse clusters of pure white little bits of fluff that look, indeed, just like the (unrelated) annual ageratums—and also, now that you think about it, like the flowers of Conoclinium's giant Summer cousins, the Joe Pyes. The flowers go with absolutely anything else in your high Summer garden, from the palest genteel pastels to rich indigos and purples to the deepest molten-lava reds and oranges.

Flowering season

Just when you need it, the height of Summer: Mid-August into September.


Plenty of sun, good soil, plenty of water.

How to handle it

You and your hardy ageratum will both be happiest when you accept its rambunctiousness.  Put its boundless energy to work for you by partnering your Conoclinium with neighbors who are much taller and so won't care if there's a lot of action at their ankles:


1. big Summer daisies (Heliopsis, Helianthus, Rudbeckia, Inula, plus the taller Fall daisies like asters and mums).  And:


2. narrow spear-like grasses like Panicum and Miscanthus, and spear-like perennials like irises and iris-like perennials like Crocosmia 'Lucifer', all of which can poke up into full sun.  And:


3. by huge-leaved clumping thugs whose foliage will keep the Conoclinium at bay, such as Silphium, sun-tolerant hostas like 'Sum & Substance'.


If you make sure it gets off to a good start, the self-seeding annual Nicotiana sylvestris would be a terrific partner to Conoclinium, adding gigantic and ground-covering foliage at ground level, plus large heads of narrow, pure white, fragrant trumpets three to six feet above ground.  


Perhaps the ultimate partner: Butterbur, Petasites japonicus.  Its huge lotus-like leaves are so thuglike in the same rich moist soil the Conoclinium craves that you'd probably need to protect the Conoclinium instead.



Divide in Spring ever few years to keep the colonies thick and happy.  Cut back by half in May or early June, which controls overall height and reduces floppiness.  Next June, I will remember to do this.


Its flowers are so ornamental, and come at such a helpful time of year, that you'd also want to have the choice of a variety that was an obedient clumper instead of an ever-eager ground-gobbler.   Alas, none yet exists, so be prepared to limit Conoclinium's spread—or to use it, as above, where an energetic groundcover is just the solution you need.


'Cori' is a pale-blue/lavander alternative, equally enthusiastic but, to my eye, only at home with pastels and whites, not the often warm-hued flowers that are more likely to be in bloom by August.


On-line and at retailers.


By division in Spring.  As typical for late-Summer bloomers, you could divide Conoclinium into individual rooted stems, all of which would still bloom by September, and be a tight-knit groundcover by the following May.

Native habitat

Conoclinium is native to Missouri.

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