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

Cowslip Clematis

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My cowslip clematis's first flowers.  Floral, light, sweet:  Now I know how cowslips themselves smell.  Too bad I'll always need to smell the flowers from a stepladder. 

 

I've planted one Clematis rehderiana at each of three legs of a pergola (whose fourth is reserved for the massive and trunk-like growth of Rosa 'Eddie's Jewel'), and there's nothing for them to climb through on the way up but the 'Altissimo' rose I planted at each leg some years ago.  'Altissimo' are ever-blooming but painfully sparse in leaves.  Cowslip clematis adds some welcome Summer foliage, but the flowers will only be at the top of the pergola.

 

clematis-rehderiana-foliage-640

 

Hence the stepladder. 

 

The fragrance of cowslip clematis flowers is light—nothing like the heavy spice of nicotiana or gingers, which you can almost see rolling towards you through the garden.

 

clemati-rehderiana-flowers-640

 

To pile on the irony, cowslip clematis flowers are tiny—no bigger than my littlest fingertip.  All the more reason, then, to savor them at close range.

 

Hence the stepladder.

 

Ah: here's a thought:  The clematis does best when cut back to its lowest leaf-buds each Spring.  Next year, instead of letting all the new stems rush upward, I'll lead a stem or two out into the surrounding beds.  This clematis doesn't like to grow horizontally, though, so the stems will still need to climb—but just gradually, inch by inch.  By the time the flowers are out in October, maybe a few clusters will be just five or six feet above ground, not ten and twelve.

 

Then, finally:  No stepladder.

 

 

Here's how to grow this fragrant late-season clematis:

 

Latin Name

Clematis rehderiana

Common Name

Cowslip-scented clematis

Family

Ranunculaceae, the Buttercup family.

What kind of plant is it?

Flowering deciduous vine.

Hardiness

Zones 6 - 9.

Habit

Fast-growing stems climb easily and, if given the opportunity, to fifteen feet and higher.  Flower clusters are at the tips of the stems.

Rate of Growth

Fast.

Size in ten years

Assuming the normal routine of "How to Handle It," below, a broad but loose canopy of foliage and flower ten to fifteen feet high and, potentially, as wide.

Texture

The jagged and toothy foliage is detailed enough—but not in overwhelming density as to obscure whatever the vine is climbing on and through—to be ornamental in its own right, and helps ease the wait for the late-Summer flowers.

Grown for

its flowers: Tiny pendulous bells, each no bigger than a fingertip, dangle from panicles that (says one expert) point at 60 degrees above horizontal no matter what the position of the stem they arise from.  The yellow flowers that verge into green are so pale they could just as well be described as green so pale they're verging into yellow.  They are sensational backed by darker foliage—but then again, what isn't?  The light floral fragrance is always described as that of cowslips.  Those of us who've never even seen a cowslip, Primula veris, let alone grown or smelled one, are grateful for this olfactory introduction.

 

its habit:  Cowslip clematis is particularly pleasing when growing through shrubbery and small trees because, although it climbs with ease and is quite vigorous, it doesn't smother everything else along the way. 

Flowering season

Late Summer: September into October.

Culture

Sun or part sun, decent-to-rich soil, and plenty of water.

How to handle it

Cowslip clematis's priorities for sun, soil, and water are strictly by-the-book for clematis.  Plant in good soil—even great soil, deeply-dug, if you can manage all the compost—so that the base of the plant gets some shade but the eager stems it will sprout can find their way into the sun.  A thick mulch can provide the shade just as well as neighboring plants and, even better, will also help retain moisture.

 

Clematis are typically a welcome exception to the rule that Winter drainage is essential.  Although they usually won't tolerate being planted in low spots where water collects, their fondness for plenty of water during the growing season has also increased their tolerance of heavy wet soil all Winter.  Cowslip clematis is no different, and will fail more often from too much heat and too little water in Summer than from too much water in the Winter.

 

In late Winter, cut the stems back to the lowest buds, which are easy to spot because they are in widely-spaced pairs.  Then stand back as the tide of new leafy stems gathers energy and acquires real estate.  Cowslip clematis is born to climb, and isn't interested either in sprawling on the ground or even growing out horizontally along, say, fence rails.  Plant it where a suitable host is within a few feet, but not right alongside the clematis' roots, which will want their own patch of rich and moist soil to themselves. 

 

The stems of cowslip clematis tend to twine into themselves, so unless your goal is to have a column of growth instead of a canopy, get a few stems started out to the sides early in the season.  Because the fragrant flowers are only at the tips of the new stems, not every foot on the way up, there's even more reason to train at least a few stems out to the sides.  You'll only be able to smell the flowers of the more vertical stems if you've gotten out the stepladder first, but the stems you've trained out more to the sides could, if you're lucky, only get five or six feet tall by the time they start flowering. 

 

Given that C. rehderiana's ambition is to climb fifteen or even twenty feet, plant it where its host is expansive enough: A very large shrub or small tree, say, where no matter how high and wide the clematis wanders, there's still host above it that's clematis-free. 

 

A contrast in foliage shape or color would be very helpful:  How about a large purple-leaved Japanese maple?  Or any of the large-enough magnolias, whose smooth-edged oval leaves are the opposite of the Clematis' multi-lobbed and jagged-edges ones?  If your goal is to have such an arboreally-hosted Clematis rehderiana, let the vine grow free-range for a number of years so it can really get high enough; if you cut it to the ground each Spring, it might never get as high as you'd like.  On the other hand, such a high-flying vine will never have flowers that you could get near, so you'll need to be content only with wafts of the fragrance from on high, not the direct dose you'll get by putting your nose right into a big cluster of blooms. 

 

At Wave Hill, in the Bronx, New York, there is a really inspired pairing with the gigantic (but clumping and non-self-seeding) knotweed, Polygonum cuspidatum 'Crimson Tower'.  Its canes soar to ten feet, and its smooth-edged leaves and millions of minute red-pink flowers are both an exciting contrast to the foliage and flower of the Clematis.  Plus, each Spring the knotweed and the clematis both get cut down to the ground.  This is much easier than the inevitable patient chore of extracting the cut Clematis stems from a woody host.

 

Another option is to train the clematis onto a wall.  Given the flower panicles' exclusively 60-degree angle from any and all stems, a wall of C. rehderiana would have a remarkable geometric consistency of floral display. 

 

The fragrance is best when the top growth of the cowslip clematis is in full sun; the vine thrives in part shade, but the scent is diminished even when the overall growth and flowering isn't.   

Downsides

Cowslip clematis is only hardy down to Zone 6.  Like other clematis, it doesn't tolerate drought or lean soil. 

Variants

Clematis rehderiana itself has yet to grace us with any immediate variants, but Clematis overall are one of many broad as well as deep plant groups that can tempt you to extravagant exploration and indulgence.  There are scores of species and hybrids, and more than a couple of books devoted just to them.  The plants provide so many nuances of color, growth, habit, and overall vigor that one of my clematis books is solely about potential woody "host" plants for this, that, and the other clematis to climb up through.  The subtle partnering of clematis and host plants is one of the ultimate high arts and pleasures of the well-thought-through garden.   

Availability

On-line.

Propagation

By cuttings in Spring, as well as layering.

Native habitat

Clematis rehderiana is native to western China.

 
 
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