Native Vs. Exotic Plants

A Case of the Hebe Jeebies

No sooner did they hit the PLAY button on my Hebe piece that aired on Morning Edition today, that it hit me, Uh oh! I'm a sitting duck for the Native Plant Police, or NPP (not to be confused with that triumverate of nutrients, NPK).

Introducing the genus Hebe, a New Zealand shrub that comes in tons of delicious foliage and

Introducing the genus Hebe, a New Zealand shrub that comes in tons of delicious foliage and flower choices but resents humidity and low temperatures. Sorry to wet/whet/worry your whistle if it's out of your hardiness zone! photo by KL hide caption

itoggle caption photo by KL

If you're unfamiliar with this family feud concerning native vs. non-native plants, you'll be surprised to learn it bears a slight but sordid resemblance to the current controversy over immigration issues right here at home.

The botanical argument goes that non-native plants have done irreparable harm to our environment. (Take a look at what kudzu, ivy and other non-delectables have done in the U.S. and you'll see the picture.) They overwhelm native plants, deprive them of their habitat, and wreak havoc with the ecosystem in countless ways.

The solution, some argue, is to banish non-native plants from the garden in an attempt to restore a very delicate balance and celebrate the inherent birthright of North American plants.

But not all non-native (aka exotic) plants are invasive. Far from it; they're some of the most sublime and well-behaved plants one could have. We'd be bereft of enormous beauty, joy and genes if we were forced to garden only with plants that were native before the Spanish, Portuguese, French, Dutch and of course English arrived.

So why do I feel like a sitting duck? Because my feature about the hebe - a wonderful New Zealand shrub - celebrates all kinds of exotics. So in an attempt to ward off any tedious mail about my non-ecological sympathies, I refer any naysayers to my last story about conserving native seed.

Alternatively, if I was defensive (I am NOT! I am NOT!), I could suggest that those gunning for me take a cold jump in a duckweed-covered lake.

I'll be the one wearing flippers...



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I enjoyed the Hebe piece very much, as I do pretty much everything you do. However, having visited the UC Santa Cruz Arboretum shortly after a very rare freeze caused wide spread damage to their beautiful plants, I think you should probably comment on what to do when faced with a very bad winter, which will happen. Has this been a problem for Hebes with their 17 degree limit?

Sent by Ken Connor | 7:51 AM | 6-28-2007

I'm not a member of the NPP, but I've always found it interesting that we celebrate the exuberant distribution of the world's most beautiful plants while we'd never tolerate an analogous unregulated dispersion of the world???s (equally beautiful) animals into our backyards.

Why is this? It???s probably because we think that animals will move to your neighbor???s yard, but plants won???t. This thinking has changed with warming climate (as Ketzel points out). It is impossible to predict which currently non-invasive plants will become problem invasives in future warmer climates. Invasive plants drive native species extinct.

Sent by Jason McLachlan | 10:12 AM | 6-28-2007

The Hebe piece this morning stopped me dead in my tracks - I am always trying new plants. I am gardening in Austin, Texas, and mostly its hot and humid - but not just right now - we are having more rain than ever. I guess, the hebe would not like all this humidity.

Sent by Hella | 11:29 AM | 6-28-2007

Is the Kudzu Moving north with the warmer weather?

Sent by Bradley Kunz | 12:12 PM | 6-28-2007

Oh, Ketzel! It's not the Native Plant Police, but the Commission for Meteorological Truth that will be after you. You've been involved in promulgating one of the great myths of Zone Denial pipedreamers: that global warming predicts increased winter frost protection...along with an ever-expanding capacity to grow more tender plants. It doesn't. Failure to understand the difference between the dynamics of AVERAGE weather phenomena and EXTREME weather phenomena is rampant in the horticultural community. Average weather is the result of local interactions of air masses. Extremely cold weather is the result of arctic incursions: polar air masses that manage to slip down into lower latitudes from remote regions of origin. Meteorologists don't agree on how a changing climate will affect record freezes. But there is good reason to believe that -- at least on the West Coast of North America -- future deep freezes will be MORE severe, not less so, than historical norms. We may well be in for hotter summers and colder winters than what we've known in the past. Yes, it's been a mild two decades. There's been a lot of sunspot activity and we're in a wet cycle of the PDO. People have always pushed the envelope of hardiness during these mild episodes, that's nothing new. But the day of reckoning always comes. Along much of the West Coast, January 2007 brought the worst freeze in living memory (at least a 50-year freeze in much of California). This despite the fact that the AVERAGE annual temperatures on the West Coast have been at record highs for the past several years. Don't go out and buy those avocado trees just yet. Changes in average temperatures do not predict changes in extreme temperatures...the Iceman still cometh.

Sent by Steve | 12:30 PM | 6-28-2007

There needs to be a piece on not bringing in non-native plants and the problems that have been caused in the past. Florida would be a good place to start then move on the the SE.

Sent by James Gibson | 1:47 PM | 6-28-2007

Living in the wilds of South Florida (zone 10 or 10.5) we are similarly spoiled with lots of stuff that grows here including the invasive and non-invasive less than natives. I wish you had mentioned about the invasive issue in the piece. Once upon a time ago they planted Australian Pines to dry up the Everglades so it could be paved ... we're still fighting this invasive, non-native, non-pine. Hang in there .... I did like the musical interpretations of the plants.

Sent by Aviva (uh vee vuh) Buschbaum (bush bow m) | 2:00 PM | 6-28-2007

There are so many things wrong with this article that I don't know where to start, so I'll pick the two easiest points. One, many of the invasive weeds that state and federal governments spend billions of dollars a year trying to eradicate ended up here in exactly the same way the Hebe did(because someone thought they were pretty). With plants, it is not only about beauty. Second, it is a complete falsehood to suggest that global warming will reduce exposure to frost.

Sent by Nate | 3:45 PM | 6-28-2007

Doesn't anyone grasp the irony of humans pontificating on the invasiveness of OTHER organisms?

Consider our history.
3 million years ago, Homo sapiens -- a tropical primate -- arose in the Rift Valley of present-day Ethiopia. For most of that time, these African hominids confined themselves to their native range, but about 100,000 years ago, began to roam extensively from their African homeland. However, they did not adapt to cooler conditions and so, at great cost to the health of the environment, they constructed energy-dependent abodes that simulated the subtropical savannah conditions they evolved under. This shows that whatever the success of their spread, they can truly only be considered "native" to the Horn of Africa.
The populations of these invasive primates saw such unbridled increase that they displaced upwards of 80% of all native organisms in the foreign lands where they became established. They also brought with them non-native felines, canines and bovines that further displaced or preyed upon native species. They engaged in widespread deforestation and destruction of native plant communities to make space for their climate-controlled communities and to establish huge monocultural stands of non-native cereal grains and fruit trees which they brought with them from other continents. In their colonizing fervor, they bred with a level of fecundity unmatched by any other organism in the history of the planet. Eventually their supernumerous presence became so burdensome to the environment that the climate of the planet began to change as a result of their activities.

And yet, these African primates will point their fingers at fellow non-native organisms in horror. Non-native! Non-native! This thing came here from somewhere else! It must be eradicated!

Sent by Steve | 3:49 PM | 6-28-2007

Good piece on hardiness zone maps this morning, but I would suggest you do a followup on microclimates and the impact of knowing your landscape well enough to use a hardiness zone map to assist in your plant purchases, but cautiously enough to use them as the most basic guide for how successful a plant will be in your location. I've been involved with horticulture as a professor and now journalist since 1959 and when it comes to hardiness the best advice is to consider most plants that are exotic as annuals!

As I have become older and spent time with folks much older than I it has become apparent that the neighbor who has gardened in the same spot for 75 years is much more useful than any map the the U.S.D.A, AHS or the National Arborday Foundation will ever create.

Happy growing, Rick

Sent by Rick Churchill | 3:55 PM | 6-28-2007

A few more comments: I would like to see discussions started about using non-native plants ...and the impacts upon the fragile eco-balance when we start growing switch grass and corn to replace oil. Any takers?

Sent by James Gibson | 4:20 PM | 6-28-2007


Yes, you are a sitting duck for the "NPP", but only because your piece was ill-conceived, irresponsible, and flawed. As Jason inferred above, it is probably most illustrative to look at how our efforts in the animal kingdom have effected our ecologies (see mongoose, house-cat, cane toad, etc.). It is both naive and arrogant to think that our actions regarding plant-life should be any different. I would like to add to Jason's argument by saying that it is also impossible to predict which introduced species will become a problem. Shouldn't it be nature, not man who decides what is invasive and what isn't. It seems to me that our record in matters of species introduction speaks for itself (see duck weed, eucalyptus (did you actually use eucalyptus as positive example?), pampas grass, etc., etc., etc.,).

P.S. Your story on seed banking doesn't get you a pass on this one. That one was a lay-up. What good is a banked seed if it is doomed to choke-out buy a pretty plant from half a world away.

Sent by Chris | 4:42 PM | 6-28-2007

I too am concerned about exotic plants and the devastation that they can potentially cause when introduced. That said, I would feel bereft at the thought of losing so many ornamental plants in my garden if the gates where to close to them. As a gardener I feel it is my responsibilty to do some careful research about the non-native plants I use. You can't rely on the trade to be careful for you. I apply the same rule of thumb to non-native plants. False Lily-of-the-Valley while a native where I live, and a beautiful groundocver beneath a canopy of native Doug firs, can wreak havoc in a garden setting.
In a city the "natural" environemnt has been so altered that often native plants are no longer an option. Perhaps I cast too wide a net of plant love, but I think that with careful and concientious attention our gardens, especialy urban ones, can be wonderful and diverse places that do not harm the surrounding ecosystems.

Sent by Kailla | 5:10 PM | 6-28-2007

Does anyone want to propose a working definition for "native"? One commmon, but embarassingly silly one, has failed to be meaninful in the past because it was based on political geography. People would say that such-and-such a plant was "native to California", for instance. Yet when we examine Landsat imagery of western North America and search for "California", we find that it isn't there. The concept of "California" is an abstraction of language that relies on human imagination to imbue it with meaning. Once outside the skull of Homo sapiens, there is no "California" or "Humboldt County" or "United States of America".
We need some more absolute arbiter of provenance than imaginary jurisdictions of human government to tell us whether a given plant is inside or outside of its proper range of distribution. In nature, the ecological niches in which plants naturally occur can be exceedingly small. A fern that grows in a riparian habitat 2 miles from your home may be an "exotic" with regard to the open exposure of your yard in the city. How far away from a wild population can a plant be cultivated and still be considered "native"? A mile? 500 miles? 500 feet?

Sent by Steve | 6:06 PM | 6-28-2007

Interesting piece about hebes - I don't think they'd survive on Cape Cod but maybe I'll try one out. Early on you mentioned a S. African shrub with peanut-butter scented leaves... what is it called??

Sent by Amy Crocker | 8:27 PM | 6-28-2007

Amy, the peanut-butter scented shrub is Melianthus major. If you can't find it at a local nursery, it's abundant via mail order.

And I wanted to let James and Aviva know I'll be heading to Hawaii in September to do a piece on the various efforts underway to re-introduce native plants into that native-dessimated region.

As for kudzu moving north, I'd like to hear from other folks about that. A report did come out two days ago in the WSJ that Toxicodendron radicans is now flourishing because of warmer winters:

Time to buy stock in calamine lotion? Or, wait, don't tell me - is this a pharmacological conspiracy altogether?

(NOTE - that's a j-o-k-e)

Sent by Ketzel Levine | 8:39 PM | 6-28-2007

Your piece on the Hebe was awesome! I don't care about the native non-native fight it was your originality that brightened my wife and mine drive to work this morning! The unique approach of touring a garden via music and your analogy of the climate zones as a piece of lasagna was so visual! Thank You; but now my gripe! What were your music choices? I looked online for the tracks used but did not seem them listed. We talked about this piece all the way to work!!

Sent by Eric | 9:40 PM | 6-28-2007

Ah, the question I longed to be asked. Thanks, Eric.

The song of the Hebe is from a flute concertino by Northern Irish composer Philip Hammond (disclosure: he's a dear friend). If you'd like, I can post the whole 2nd movement on a future blog. In fact, that's really the only way to hear it again, since it's not in commercial release.

As for the other two - umm, umm - I'd have to do some digging. Never thought :06 of any music would warrant a query, but if you want me to track them down, I'll do it. (arf! arf! anything for praise like yours).

Sent by Ketzel Levine | 9:56 PM | 6-28-2007

Where in Portland is 17 degrees a "warm winter day"? You must live in NORTH Portland - it rarely goes below freezing in my part of town, and I live at elevation.

Sent by SAS | 9:58 PM | 6-28-2007

Being a native-born New Zealander who now lives and gardens in Southern California pretty close to the coast, I have a few New Zealand native plants to keep me company in my garden - flax, of course, cordyline, nikau palms (the only ones I've seen in the U.S. outside of the very handsome specimins in Balboa Park in San Diego), but alas, no hebes. Not for want of trying, which I have done on two occasions now, but both times the plants turned up their toes pretty quickly. Definitely can't be the cold or humidity since as you know we don't get much of either here in Orange County. Perhaps the locations was just too hot for them. This has been pretty tough on my reputation as someone with very green thumbs. Thanks for your piece on one of my favorite memories of "home" - I was pretty surprised to hear a piece on hebes. Now how about "nikau" palms - one of the most handsome of palmsn in my opinion, and they seem to love the climate here and I'm sure would do well far north of here.

Sent by John C | 10:32 PM | 6-28-2007

John, here's a news flash I received from our community earlier today.

Instead if it simply being humidity that hebes hate, it is more likely the absence of cool summer evenings that do them in here in the USA. That would explain why the genus thrives on the Oregon coast where there is "high" humidity (not like the east coast, of course, but still high).

So, yeah, you're basically SOL re:hebes in Orange Co., but at least you now know why.

Sent by Ketzel Levine | 11:47 PM | 6-28-2007

RE: nikaus. I'm trying out some nikaus here on the southern coast of Oregon. I have the regular Rhopalostylis sapida as well as the Chatham Island form. They seem to be doing quite well at Strybing Arboretum in San Francisco, so their most northerly limit on the West Coast seems yet to be located. If I'm not past that limit, I'm sure I'm close to it. Because they are so slooooooow, they will unlikely become very popular. My 10-year old specimen is only about 24" tall, and a 4-year old I grew from seed has yet to throw a completely pinnate frond. It's difficult for nurseries to make any money selling palms that make such paltry growth, so they will most likely remain Holy Grail plants for a few hard-core geeks willing to grow them from seed.

Sent by Steve | 12:44 AM | 6-29-2007


The nikaus I referred to in my yard have actually grown quite quickly. I actually bought them online about 8 years ago from some guy in Central California. One was about 18" and the other about 12" when I bought them. They have absolutely thrived in my yard and the bigger of the 2 is now probably about 10' high at least and starting to develop a nice trunk. They get a little sunburned over the summer, so look their best in the winter. I'll take a picture over the weekend and post it on my website and then post a link to it here. Yes, this is slow, but patience is part of being a gardener, right? And you don't typically see palms with this kind of upright growth so it's a refreshing change and quite a show-stopper for visitors who have never seen a palm like this before. The king palms I planted at the same time were about 3' high then, and now tower at about 25' to 30'! The extremely slow grow you are indicating for your nikaus might suggest you are almost at the limit of their growing range for the west coast.

Sent by John C | 2:40 AM | 6-29-2007

Ketzel and All,

I enjoyed the piece on Hebes and I will admit that the first thing that popped into my mind was their impact on native species. Here in Montana we are fighting "pretty" spotted knapweed. Go to Missoula and look up at the mtns that surround the area. There are no native plants left. And there is nothing that kills spotted knapweed.

I can appreciate that maybe a distinction between "good" and "bad" non-native plants could be the ability, or inability, to crowd out native species. I think this is important. Our own North American wildlife depend on native species for their own sustenance.

I just want to make sure that we, when admiring non-native plant species, don't do in our own native wildlife.

Sent by Lynn Thomas | 5:28 PM | 7-1-2007

It is true that invasive plants are, by definition, non-natives. That doesn't mean, however, that non-natives are, by definition, invasive...or even potentially invasive. Such a syllogism represents a a fallacy of inductive generalization known as "converse accident": using exceptional specific cases as the basis for a general rule, i.e., if all A have the attribute B, then all those who have the attribute B are potentially A. This is the same kind of fallacy of generalization that leads to all manner of human prejudices:

"Since all the terrorists aboard the plane were Muslims, we must be wary of Muslims due to the likelihood that they will be terrorists".

Sent by Steve | 2:40 PM | 7-3-2007

OK, now that all the hothead hortheads have gone off to berate someone else about some PERCEIVED aggregious error, I'd like to weigh in on this fray.

Hebes do not have any of the characteristics of invasive plants. They do not creep, they do not set prolific seed, and while they root readily, they cannot take their own cuttings and plant themselves. The only place they thrive in this country is along the NW coast. Beyond that, forget it.

But on a more personal note...even though I've been told to get a thick skin if I'm going to blog...

I wouldn't even CONSIDER profiling a plant that might have any invasive characteristics. Simply because THIS piece wasn't about invasive exotics is absolutely no reason to assume I am ignorant about this issue.

I'm loathe to point out that I've been reporting on it since the early 90's...that I've done several slide show presentations for botanical organizations (including an intro-level slide show at ..
and and have participated in local and national workshops about native alternatives to invasive plants.

But there, I've said it.

The good, no GREAT news have been the responses from people like Lynn, whose first thought on this Morning Edition feature was, "uhoh, are hebes invasive?" Her reaction proves that those of us who've been spreading the word for decades have been heard.

Sent by Ketzel Levine | 1:46 PM | 7-8-2007

To bring the issue to a finer level of definition, I would argue that it is not the plants themselves that have invasive tendencies. One really has to look at the PLANT-CLIMATE INTERFACE to nail down what creates invasiveness. In general, plants become invasive when they become established in an environment that is more fecund than that in which they evolved. The precipitation season has much to do with this. Climates with significant rainfall in the growing season offer greater fecundity than those with dry summers. Many people from the East Coast, for example, are horrified to see West Coast gardeners cherishing a specimen of Ampelopsis brevipedunculata -- porcelain berry -- in their gardens. But it isn't rampant on the West Coast because summers are dry. The same can be said for many other plants. Kudzu, though not that often seen here, does exist on the West Coast where it is well-behaved and self-limiting. Many plants that are prim and popular in California landscapes (hedychiums, for example) are a horror in Hawaii. The line of safety can occur quite abruptly. Crocosmias are a horribly invasive weed on the Oregon Coast, yet Oregonians who live in the Willamette Valley 60 miles to the East, actually BUY these bulbs at nurseries to decorate their gardens. So you have to consider both YOUR climate as well as the plant in question to evaluate invasive potential.

Sent by Steve | 1:14 PM | 7-15-2007

The process of invasion, naturalization, extinction is certainly not new. Species movement has been occuring for as long as 'species' has even been a potential concept; albeit accelerated dramatically by humans. Although I am loathe to negligently (or purposefully) introduce something that might cause a percieved problem in the acute sense, I wonder how much it really matters in the grand scheme. After all, the only constant is in fact change. Just a question to ponder.

Sent by mike | 3:07 PM | 7-15-2007