redbuds, mahonia and more, with j.c. raulston arboretum’s mark weathington

WHO TRACKS DOWN exceptional plants, puts them to the test, then helps the best of the best to find their way into the nursery trade and therefore into our gardens?  One such place we gardeners have to thank for that work is the J.C. Raulston Arboretum in Raleigh, N.C.

On my public-radio show, Arboretum director Mark Weathington took me through the years-long process of “discovering” new plants. Plus, Mark highlighted some Arboretum specialties that may belong in your garden, including standout redbuds and mahonias, and the lesser-known evergreen shrub Illicium, and even showy native dogwoods selected to withstand increasingly saline soils in tricky coastal areas.

What’s now called the J.C. Raulston Arboretum at North Carolina State University is where I met my first Cephalotaxus–a near-lookalike to our common evergreen yews but excitingly deer-resistant. And then a moment later I met another one–this time a columnar form–and then another that was sprawling and groundcover-ish. And the tour went on like that: genus by genus, collections of great potential candidates for my landscape in all their range of variety–except that I had never heard of them.

The person showing me those plants was the arboretum’s namesake, J.C. Raulston, who died in 1996. The place is now 10-1/2 contiguous acres of collections and gardens whose mission is to:

“…introduce, display, and promote plants that diversify the American landscape, thereby benefiting our communities economically, environmentally, and aesthetically, as well as provide educational experiences to the general public, students of all ages, and the green industry.”

Well, I think I got some of all of that from my memorable visit years ago.

Read along to the Jan. 30, 2107 edition of my public-radio show and podcast using the player below, as you listen to my conversation with Mark Weathington (seen in next photo at the Arboretum’s new front gate). You can subscribe to all future editions on iTunes or Stitcher (and browse my archive of podcasts here). Information about visiting the Arboretum and events there are at the bottom of the page.

great redbuds, mahonias and more, with mark weathington



Q. I have such a fond memory, as you heard, of my visit many years ago to the Arboretum. Tell us a little bit about it, and about J.C. Raulston, for whom it was named.

A. J.C. came to the Arboretum back in 1975. We date the beginning of the Arboretum to that next year; he came late in the year, so we say 1976.

Q. [Laughter.]

A. J.C. was more of an “ask forgiveness, not permission” kind of person. When he came to N.C. State, he was tasked with helping grow the nursery industry. He had been in Florida and Maryland and Texas, and very early on he saw that everywhere he went, there were about 40 plants that made up 90 percent of the nursery market.

Q. Yes.

A. Different plants in College Station, Texas, than in Raleigh—but just 40 plants. His thinking was: “How do you grow the industry if everybody’s growing the same thing?” How do you make people make more money; how do new people come into the industry? There’s just no growth; it’s a dead end.

So he set about to, as he said, “diversify the American landscape.” And to that end, he just collected plants wherever he could. He traded, he visited gardens, and he planted everything out to see what would grow, because there were a lot of things we were told won’t grow. As you know the plants don’t always read the plant books, and don’t realize that they can’t grow.

Q. [Laughter.] Indeed. So that was in 1975 and then 1976, when you make the official beginning. Has the property gotten bigger?

A. The property has gotten bigger. It started off that J.C. was using a portion of it, and he pretty quickly got to about 8 acres. Then we added on another couple of acres in the last seven or eight years. It’s small. People who know us by reputation get here and are amazed at what we do in such as small space. We’ve got about 6,500 different types of plants, mostly trees and shrubs, here in that 10-1/2 acres.

Q. 6,500—and they’re not all miniatures? [Laughter.] And it’s not, as I mentioned in the introduction only about looking at one Cephalotaxus and another, at collections of things that he had passions for, but there are these incredible gardens. I remember seeing, even a long time ago, a perennial border the scale of which I hadn’t seen before really in the United States. It was spectacular. So you have these gardens also. [Above, a portion of the perennial border.]

A. And we still do that—we actually probably have fewer plants in collections like when you visited. We put them in landscape situations to see how they grow; we really want to look at them under real-life conditions.

We do very little watering at all, and basically no pesticides. Every once in awhile we’ll do something when a plant is getting established, but we are evaluating the plants. We want to see if insects are eating the plants; we want to see if they get diseases.  And then we know that’s not a great plant. We want to see if they suffer drought stress when it’s very dry, or when it gets very cold if they get damage. We want to tell people what these will do if they grow them.

Q. One of the other assets that people can enjoy even if they can’t visit—and of course I’ll advocate that everybody does visit—is that you also have this digital or virtual asset in the website, almost an encyclopedia of plants. How many images does it contain?

A. We have about a quarter of a million images on the website. Not all of them are plants; some are places, because we have J.C.’s really prolific slide collection, like 90,000 images, including photos of nurseries because he taught nursery-maintenance classes.

Most of our staff—all the horticulturists on staff—we load our images into there and they are labeled. They’re mostly correct, though once in awhile something slips through…

Q. [Laughter.]

A. …and it really is a great resource for finding plants.

Q. I stated in the introduction that part of your mission is a mandate to collect exciting new plants, and I suspect when I say that, it may conjure images for my listeners of plant explorers trekking to remote jungles and mountaintops around the globe to find the undiscovered. But that’s not exactly all you’re doing, is it?

A. We do domestic and international collecting, and people do have this wild vision of some foreign land. But quite a bit of what we do is collecting here in the U.S. We collect through North Carolina, through the Southeast. We go to some places that you wouldn’t think plants would grow, like the drier areas of Texas and Arizona, and to the Pacific Northwest.

But a lot of people think, “looking for new plants.” My wife in fact asked me: “When is there going to be a plant named after you?”

Q. [Laughter.]

A. It’s not that we’re discovering undiscovered plants, necessarily, although that does happen. We’re looking for plants that are a little different from what we grow in our gardens. Maybe it’s a tree with a different color flower—or we look for them on the edges of where they grow.

An example: In North Carolina, one of the big problems as you get to the coast is that the groundwater is becoming increasingly saline, and it’s really causing issues. So we go and look for some of the westernmost flowering dogwoods that are growing out in Texas and Oklahoma, that are growing in basic soils that have really high saline content. We go collect those, and grow them out, and see how they grow in our very acidic soils here at the Arboretum, but also get them in the hands of nurserymen who are struggling with some of these cultural issues.

Q. So you’re talking about our native Cornus florida.

Two things that what you just said bring up: One is that people who aren’t gardening in the South or Southeast shouldn’t hang up and stop listening to the podcast [laughter]. Even though I’m in the Northeast Zone 5B, almost in New England, and couldn’t be more different if you look at the map, I have a lot of incredible native woody plants in my garden that I have cherished for decades that are native to the South and Southeast.

Like Aesculus parviflora, the bottlebrush buckeye, and Fothergilla, too, yes?

A. Exactly. And many of our native plants were pushed down with glaciation. The glaciers retreated, but the plants didn’t necessarily go with them—they stayed here in the South, and they’ve got incredible hardiness. But if they’re not trialed in those areas, you’ll never know.

That’s the other side: We grow the plants out and see how they do, and then we get the plants into the hands of nurserymen and other gardens and enthusiasts all over the country and world with one expectation: that people tell us how the plants do where they’re going, so we know if they’re hardier than we think as we send them farther north.

Q. So a Cornus florida is not a Cornus florida is not a Cornus florida—there are many different…what do you call that, different forms, like when you find that one that’s adapted to the saline soil conditions, for instance?

A. It depends; if it’s different enough, it can get a variety or form name. But with something like Cornus florida, it all intergrades so smoothly—kind of a bell curve—that you can look at them on either end of the spectrum and say, yes, these are different enough to be different varieties. But then if you look all across their range, you think, well no, maybe not, because they get a little bit different, a little bit different, a little bit different.

So what we would do, because we want to introduce plants into the nursery trade and get them growing in landscapes and gardens, is we would grow out plants of say this Cornus florida. We would sow seed from it, we would watch the seedlings, and then distribute them, and the ones that were the best and more tolerant of the soil conditions, and maybe had larger flowers or better powdery mildew or anthracnose resistance—we would put a name on one or two of the best; Texas Star,’ or something like that, so that people know what they are getting.

Q. I was excited to learn that the Arboretum has a passion for Cercis, for redbuds. I’ve oddly enough never had a redbud in my garden and don’t know why, but each year at redbud time I think: “Why don’t I?” [Laughter.] Tell me about that genus, and exceptional things about it that I should be on the lookout for (or people in other places, too).

A. Cercis is a very interesting plant, because there is not as wide a number of species as many people might think. There are relatively few species of redbuds, but they grow all over the world. We have them on the East Coast all the way into Texas, and that’s all basically the same species: our Eastern redbud, Cercis canadensis [Zones 4-8].

Then into Mexico you get Cercis mexicana, a much different plant, and then the West Coast has Cercis occidentalis. In Europe there is Cercis siliquastrum, and then there are four or five or six species in Asia, so really a broad distribution.

The redbuds were a particular favorite of J.C.’s when he was first starting the Arboretum. He collected them, and then one of our previous directors, Dr. Denny Werner, was breeding redbuds, so the Arboretum introduced several, and we’re still breeding redbuds.

Q. What are some of the named introductions?

A. Let me step back a moment first: The Texas form of the Eastern redbuds, Cercis canadensis subspecies texensis, is different from what we see here. It has a very glossy, thick-textured leaf, which makes it more sun-tolerant, because it’s normally an understory tree, and also makes it more drought-resistant. That makes it a better landscape tree.

We took the popular ‘Forest Pansy,’ the popular purple-leaf redbud that people grow quite a bit, and bred that with the Texas form, and came up with ‘Merlot.’  It has that thick, glossy leaf—more of a rounded than a heart-shaped leaf, but with that deep burgundy. We also bred a weeping purple one called ‘Ruby Falls,’ and a variegated weeping form called ‘Whitewater.’ [Images above of ‘Merlot’ leaf detail and tree from NC State Department of Horticulture. Below, ‘Whitewater.’]

Q. Is the variegated leaf green and white or green and yellow?

A. Green and white. They are really some amazing plants.

We have collected all these redbuds all these years and watched them grow and looked at them. So one plant that had been in our collection for at least 15 years or so, a Chinese species called Cercis chinensis, that every year we’d say, “That is so much better than everything out there.” It’s the first to start flowering, and the last one to finish flowering. It has a really good color.

We finally decided to go ahead and introduce that one, because we’ve been watching it so long, and it’s called ‘Kay’s Early Hope’ [below] for NC State basketball coach Kay Yow, who passed away from breast cancer. It flowers right then during March Madness with that lavender-pink flower, so every year it honors Kay Yow.

We just think redbuds are such good trees for the modern landscape. They are relatively small stature—all the redbuds—and they flower very, very heavily. They’ll grow in sun or shade, and are easy plants to work into people’s landscapes.

Q. Let’s move on to Mahonia, and with a common name of “Oregon grape” one might infer it’s native to the Pacific Northwest—so what about them?

A. That’s another one that J.C. kind of started with—but there really weren’t many plants that J.C. didn’t like. It’s kind of redundant to say it’s a plant that J.C. loved.

Q. [Laughter.] I was going to say…

A. Mahonias are in the barberry family, and in fact some taxonomists lump them in with barberry, though you’ll never see a gardener confuse the two. They are in the same family as Epimedium, too, and mayapples—which is odd.

The Mahonia are native from the Pacific Northwest and go all the way down into Mexico—there are many species, even into Guatemala and Central America. Most of those are not very hardy. And there are very many over in Asia, in China, Taiwan, Japan.

Q. Our North American one is what species?

A. There are a few—but now you are going to make my mind go blank.

Q. That’s OK; when I am giving tours in my garden, people say, “What’s that?” and I look at a plant I have had for 30 years and have no idea. [Laughter.]

A. The most common one is Mahonia aquifolium [Zone 5-8], that’s the one most people are going to see.

Q. Aquifolium: It means “leaf like a holly,” right?

A. Leaf like a holly, yes, exactly. The other one you get in the Pacific Northwest is Mahonia nervosa [above, for Zones 6-9], which is low-growing and very attractive. Down in Arizona and the drier parts of Texas there are a few of them: Berberis trifoliolata and Berberis haematocarpa and fremontii. Those tend to be really very prickly kind of nasty things. Interesting thing is that I had grown those for years, and we were out and Mahonia trifoliolata was flowering, and I had never noticed before but it had the most amazing chocolate scent to it. I don’t know if they are all like that or just our plant but it was amazing.

Q. They have this profusion of yellow flowers, yes? [Above, photo from NCSU Extension website by Domaine du Royale; fruit photo below also from NCSU.]

A. There are a couple with red flowers, but most are yellow.

Q. And then beautiful fruit.

A. Blue fruit, and some of those spiny ones in the Southwest that get closer to barberries in appearance have red fruits as well, but typically what people will see in the garden center and can find and grow will have those beautiful blue fruits.

And they flower here [in Raleigh], depending on the species, mostly in fall or in the middle of winter. Right now [late January], in winter, we have Mahonia in bloom all over the Arboretum, and there is not a lot out that’s doing that. Today it is 68 degrees here in Raleigh.

Q. Oh, shush. [Laughter.]

A. Rub that in for those of you who live up in the frozen North. But the bees are active all winter long when we get these warm days, and we need plants the bees can feed on. Mahonia are great for that.

Q. And I wanted to hear about Illicium—another beauty I saw on the website. [Photo of Illicium floridanum flower detail above from NCSU website, by Scott Zona.]

A. They’re Asian and American evergreen shrubs that are quite hardy, into Zone 6 many of them. One of the tropical Illicium is star anise—the spice. They have these beautiful starburst flowers that are red or white. The fragrance isn’t wonderful, but the foliage is nice and here’s the kicker: It’s an evergreen shrub, and deer stay away from them.

Q. Oh, yippee.

A. I won’t say anything’s “deer-proof” but they are the last thing in your garden a deer is going to touch.

Q. And when do they bloom?

A. Depends on the type, but mostly spring and summer. They’re beautiful.

Q. Is the flower followed by anything—a fruit or seedhead?

A. It’s a green fruit that looks like the star anise, but it is green and kind of fades among the evergreen leaves, so not super-showy. There have just been a couple release this year from N.C. State that are dwarf, and only get about 4 to 6 feet tall. One is called ‘Scorpio’ with red flower, and another is ‘Orion’ with white flowers.

Q. How hardy again?

A. Many of the species are hardy easily into Zone 6, and since they’re evergreen, when you start getting up farther north, you need some protection from really cold winter winds that dry them out and start damaging them.

Q. Not that that ever happens to any broadleaf evergreens here in my garden—never, ever at all. [Laughter.]

I’m so glad to get to speak to you, Mark, and hope you will come back when your book from Timber Press, “Gardening in the South,” comes out in May. Thank you.

more about the j.c. raulston arboretum at n.c. state

prefer the podcast version of the show?

MY WEEKLY public-radio show, rated a “top-5 garden podcast” by “The Guardian” newspaper in the UK, began its seventh year in March 2016. In 2016, the show won three silver medals for excellence from the Garden Writers Association. It’s produced at Robin Hood Radio, the smallest NPR station in the nation. Listen locally in the Hudson Valley (NY)-Berkshires (MA)-Litchfield Hills (CT) Mondays at 8:30 AM Eastern, rerun at 8:30 Saturdays. Or play the Jan. 30, 2017 show right here. You can subscribe to all future editions on iTunes or Stitcher (and browse my archive of podcasts here).


(Photos from J.C. Raulston Arboretum website or Mark Weathington, except NCSU Horticulture images as noted.)

  1. Dee says:

    A Mahonia side note: 10 years ago I dug up three Mahonia bealei plants when “babies” started popping up in our central Virginia woods. A decade later, I’m still finding them, pulling up over 20 last winter and this winter six or seven (so far) during the annual search for English ivy, barberry, and autumn olive. Would aquifolium escape? I so enjoy A Way to Garden and learn something with each post!

  2. Kathy Seaton says:

    I love the Raulston Arboretum, but am surprised that they feature mahonias, which are listed the NC Native Plant Society as an invasive species of significant threat, and certainly they are showing up in our woods, although not yet at least outcompeting the privet.

  3. Laurie says:

    I very much enjoyed this post. Though it’s only a bit more than an hour away, I’ve not been to the Raulston Arboretum. It’s definitely on my bucket list now, along with some new plants to explore. Thanks!

  4. Bill PlummerI says:

    MARGARET, Did you discuss hardiness of the southern/Texas forms of Cornus and Cercis? It is my understanding that they do not harden off. Nor did you discuss Mahonia bealii or M. repent. Both of these suffered badly of a bitterly cold and windy winter. They were killed back, but have recovered. NorthCarolina can grow a much broader range of plants, but I still like it up here in the southern tier of New York.

    1. margaret says:

      I did not, and I do badly with some broadleaf evergreens that technically survive but look like hell by winter’s end. I added the Zones in the story for the plants that were more adaptable to the North, but not the rest.

  5. Sally C. says:

    Not a comment, a question.
    Recently, you mentioned pruning fruit trees at this time of year. Is this also a good time to prune boxwood?

    1. margaret says:

      Hi, Sally. Here in the North, we like to wait to let winter do its thing and prune usually in early spring if they need shaping. Technically you could prune off stray bits anytime, and I know some people in more favorable Zones who do it in time to gather some holiday greens…but in my cold Zone I’d hesitate to do that.

  6. Lacey says:

    Hey Arthur, I live just a few mile away and I was just there this weekend. Lucky us! One of the volunteers shared a few seeds of a beautiful dark purple lyre-leaf sage with me a few years back, It has become one of my favorite plants. It requires no care and is far less weedy than the lyre-leaf sages that grow in Omstead.

  7. Kathleen Harwood says:

    I was heartened, and surprised, to read that cercis canadensis is hardy to zone 4. What about all the interesting varieties discussed? Equally hardy? Ive always been cautioned that they are marginal in zone 5.

    1. margaret says:

      I don’t know specifically about each one, Kathleen, but I was interested to see the range map of states reporting Eastern redbud populations. Some sources say Zone 4B is the hardiest it is; some just say 4 without being specific; others 4A. Generally speaking I am more inclined to want to invest in a selection or nursery stock from a northern breeder/grower if I’m trying a marginally hardy plant, than to risk it.

  8. Kathy in pawling says:

    Hello Margaret. So the redbud I bought on sale about 15 years ago had several of its main branches split so I had to take it down. But in its place are several suckers. Will any of these grow into a new tree? Or will it be more of a shrub? Any thoughts? Thanks for your marvelous blog.

  9. Mary T says:

    Margaret – are you interested in tree peonies? We have a wonderful collection at the arboretum where I work and I know just the man that could tell you all about them for one of your podcasts.

  10. Lauren says:

    Lovely post, thank you, Margaret. I’m in CT and wonder if you have a source for Cercis chinensis ‘Kay’s Early Hope’ in New England? I’d like to create a shady line of redbuds along my stone path.


    1. margaret says:

      I don’t, but I do see several wholesale nurseries are propagating it, so I’d ask my best local nursery to track one down for me. That’s how I have acquired most of the less-common things I have here — by special order. Sometimes it takes awhile (until their next order from that supplier is coming in by truck), but for example Windy Hill in Gt. Barrington MA has ordered many oddball things for me over the years from wholesalers. Broken Arrow in CT is also very plugged in to access to unusual things, so I might call them, too, to see if it’s something on their radar.

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