Native plants – The Garden Professors™

Mitchella repens … Partridge Berry … an Evergreen Native Groundcover for Shade

Partridge Berry in its Natural Setting

One of the questions that came up regularly when I was working the hotline at the local county Extension office, is a recommendation for an evergreen ground cover for shady spots. I had the same issue when I created my own shade garden … something that would have year round interest, but complement my desire to emphasize native species, although that was only one consideration.

The solution was literally right next to me, as a walk in my woods revealed with the lovely plant Partridge Berry, or Mitchella repens.

Not only is Partridge Berry (Mitchella repens ) beautiful, evergreen, shade-loving, and native to Eastern North America, but there’s also a fascinating aspect about its flowers and fruit, from a botanical, and evolutionary point of view.

According to the U.S. Forest Service Celebrating Wildflowers website, the “… genus name Mitchella was given to this plant by Linnaeus for his friend John Mitchell, a physician who developed a method of treating yellow fever. The species name repens refers to its trailing or creeping habit.”

Here’s the part I found fascinating: The plant is dimorphous, meaning “occurring in two forms”:

In late spring, two beautiful white flowers (with one calyx) each open their four petals to entice insects to collect their nectar. Each blossom has one pistil and four stamens. The pistil in one is short and the stamens are long. In the other it is just the opposite. … Because of this no flower can fertilize itself–all flowers must be cross-pollinated by insects, and both flowers must be pollinated to get a single healthy berry. A berry will stay on the vine until after the blooms appear in the spring unless a hungry bird finds it nestled among the fallen winter leaves.

How cool is that? The twin flowers produce, together, only one berry.

Here’s a closeup, where you can see residual evidence of the fusion. The berry is edible, and persists through the winter, assuming it is not consumed by “ruffed grouse, northern bobwhite, sharp-tailed grouse, and prairie chicken.

The fruit is also “frequently eaten by raccoons and red fox” and it has been reported that “partridgeberry made up 2.9 to 3.4 percent (dry weight) of the summer and fall diets of white-tailed deer.”

Here’s a picture of the two flowers in bloom.

It’s easiest to spot the plant in its natural setting while hiking in late Fall, or early Winter before snowfall, or early Spring after snowmelt.

Back to the Forest Service article:

Some gardeners consider Partridge Berry a must for winter gardens. During the cold days of late winter Partridge Berry is a treat to the eyes with its deep, dark-green leaves and occasional scarlet berries. In a garden setting this evergreen prefers shade, accepting the morning sun. Partridge Berry is extremely difficult to propagate from seed.

The best way to introduce this native into your garden is through 1 year old cuttings or by division. In the garden situation they will form a thick, substantial ground cover. Once established they are relatively trouble free with the only required maintenance of keeping garden debris from covering the mats.

As always, do not wild collect plants from public lands and only from private lands when the landowner grants permission. Partridge Berry is a commonly available plant from native plant nurseries especially those who specialize in woodland plants.

I love the symmetrical variegation in the evergreen leaves, a bright, light yellow line bisecting each leaf, and the delicate, less visible veins.

It’s a great alternative to Vinca, an introduced species from Europe that appears on invasive species lists in our area.

A Google search will reveal many potential on-line sources for buying Partridge Berry plants, or check with a local nursery, or independent gardening center in the native plant section.

Perennial Funday: Eriogonum allenii ‘Little Rascal’

I’m going to keep posting about perennials that deserve more attention until somebody makes me stop. The fact that my subject is, once again, yellow… is merely coincidental

Definitely was a crowd favorite during the Perennial Plant Association annual Symposium’s grower tour (mentioned in my previous post). These photos were taken at Emory Knoll Farms north of Baltimore; I believe that they were trialing and/or including it in their plant selection for green roof use.

Eriogonom allenii 'Little Rascal' at Emory Knoll Farms — Eriogonom allenii ‘Little Rascal’ at Emory Knoll Farms

Thanks to Mary Vaananen, Jelitto’s North American operations manager (and goddess of perennial plant knowledge), who just happened to be standing next to it, full of 411, when I squealed “WHAT the (blankety blank) is THAT?!” My compadre Paul Westervelt added more info, as he’s also a plant geek deluxe (and manager of the annuals and perennials section of Saunder Brothers Nursery). D’oh. Plus you rock gardening fanatics probably know this cutie as well (I may have first seen this in one of Joseph T.’s talks, now that I think about it).

Eriogonum allenii, shale barren buckwheat, is native to counties that comprise the Virginia Highlands plus those on the West Virginia side of the line in the same region. Within these counties, the scattered populations reside in the botanical wonderlands called the shale barrens.

This floriferous selection ‘Little Rascal’ is indeed from Jelitto, so you too can obtain seeds of this rarity (along with detailed germination/growing instructions). Jelitto lists hardiness to USDA zone 5. As with most species from the barrens, it requires plenty of sun and excellent drainage.

Stocky and slightly shrubby in habit, the coarse grey-green green foliage was, when I saw it at the end of July, completely smothered in deep gold flowers. Simply gorgeous. It was abuzz with bees of all sorts, including insanely happy honey bees that could barely attain lift-off. I have a plot of regular-old-buckwheat (same family, Polygonaceae), but our spoiled-rotten bees always seem underwhelmed. Wait till they get a load of this!

A Little Woodland Wonder

What’s that bit of green poking through the fallen leaves and forest duff? You’ll have to crouch down to get a good look at Wintergreen (Gaultheria procumbens). A mere 3-5″ tall, this teensy shrublet from the Ericaceae family (blueberry, azalea) has little oval leathery leaves, often mottled with purple or brown. A few urn-shaped pink to white flowers appear in early summer are followed by bright red berries. The berries persist well into the winter and help to distinguish it from similar-looking seedlings of mountain laurel or deerberry. When in doubt (or to clear your sinuses), break a leaf in half and inhale deeply. Yes, this humble little plant is the source of methyl salicylate – wintergreen oil – one of the active (though now synthetic) ingredients in IcyHot, Ben Gay, and other lifesaving remedies. Though non-scented versions are now available, that distinctive aroma alerts those nearby that you are an ATHLETE. Or perhaps just getting older*. Another common name is “teaberry” – hence the name of Clark’s chewing gum, flavored by the same compound.

Wintergreen is native throughout the Appalachians from north to south (USDA Hardiness Zones 3-8). Despite the pungent scent, when the acorn supply is low, deer will turn to wintergreen as forage. Birds, squirrels, chipmunks and others snack on the little red wintergreen berries, also redolent with the oil, and presumably have the freshest breath in the animal kingdom. In the garden, wintergreen does best in the shade of deciduous trees in acidic soil rich with leaf mold. Add wintergreen to the long list of N. American natives that have become wildly popular overseas but are under-appreciated here — it’s one of the top-selling nursery plants in Europe. Mix it up with Hellebores and hardy cyclamen to add some wildlife-friendly winter interest in the woodland perennial garden.

I can't find my own darn photo at the moment, but here's Gaultheria procumbens courtesy of Hedwig Storch and Wikipedia Commons. — I can’t find my own darn photo at the moment, but here’s Gaultheria procumbens courtesy of Hedwig Storch and Wikipedia Commons.

*Speaking of older, honk if you remember the “Teaberry Shuffle.”

How Can Natives and Exotics Possibly Coexist?

Natives vs. exotics. We’ve heard that before haven’t we Bert? Well, here’s an interesting little nugget published recently in the journal Ecology Letters. Exotics and natives are different, and their differences allow them to coexist. In this study exotics were superior to natives in terms of growth, but were fed upon more by herbivores. Interesting. Of course there are lots of different types of exotics and natives, but the plants that these researchers looked at had been living together for about 200 years. I think that’s something that the invasive extremists and apologists consistently forget – until relatively recently the average person didn’t spend that much time thinking about native or exotic, and yet the world never turned into a desert and neither the natives nor the exotics disappeared. I’m not saying we shouldn’t think about native vs. exotic differences at all, just that sometimes we concentrate on this distinction too much. Plants tend to be able to fend for themselves.

The good, the bad, and the ugly. A reply.

Ginny Stibolt of the Florida Native Plant Society recently posted Native Plant Issues: The good, the bad and the ugly, featuring me as the ugly. I posted a reply on her post, which I include here. To keep things in context, I encourage you to read her post first.

Enjoy your weekend!

Hi Ginny:

Some comments and a few points of clarification.

On the first item, as a Federal agency the USDA is bound by the Executive Order on Invasive Species which defines natives as species that occur in an ecosystem “other than as a result of an introduction”. I suspect they tried to simplify the language for the National Planting day release when they substituted ‘naturally occurring’.

On the Arbor Day Foundation, I am fairly certain they use contract nurseries in various locations for their tree sales. In any event, they have plenty of trained foresters on their staff that understand the importance of provenance and they would not send trees from northern seed sources to Florida or vice versa. But I certainly can’t fault the idea of supporting the Arbor Foundation, declining their trees, and buying trees from a local nursery.

On the Google + Hangout discussion no one was ‘booted off’. These were straight and simple technical issues. If people watch the Youtube video, the audio sounds like Neil Armstrong on the moon. This is a new technology for most of us and we are dealing with some growing pains. I would have much preferred even numbers on each side. Having an imbalanced debate can work against the majority, too. As Wilt Chamberlain famously observed, “Nobody roots for Goliath.” That said, we did have a lively and cordial debate and I hope people will bear with the grainy images and tinny audio and take a look.

Kentucky coffeetree

I haven’t watched the video but I don’t think I said there were no natives that could be used as street trees here in Michigan. If I did, I misspoke. That might be true for Linda in the Northwest – if you look at the native tree list for King county you’d be hard pressed to find anything that could be recommended in good conscience as a street tree. We have a few more options here in Michigan. If we were looking for a street tree for Lansing or Detroit the list could include hackberry, honeylocust, Kentucky coffeetree, tulip poplar, swamp white oak, and red maple. But even this list makes urban foresters cringe because they think red maples are already over-planted, tulip poplar is weak-wooded, and hackberry is difficult to transplant. With regards to Mary Wilson’s comments, there is a distinction between street trees and landscape trees. Landscape trees could be anywhere on a residential or commercial landscape where they could receive irrigation or other care so there is broader list, in contrast to street trees found on street sides in tree lawns or tree pits. Street trees are subject to the ‘worst of the worst’ in terms of environmental conditions; minimal rooting volume, compacted soils, road salt, and reflected heat load; but they provided the ‘biggest bang’ in ecosystem services, especially cooling buildings and sidewalks.

Swamp white oak

This has been an interesting discussion and clearly I have touched a nerve. I have to confess I have never been vilified so much in my life, which has been a little discomforting but also strangely flattering. When I met with Jeff and Linda earlier this week Jeff commented, “Wow, I’ve never been able to sit across the table from the devil incarnate before!” Fortunately, I work in academia where we spend most of our days telling one another how stupid the other is. People that seek to avoid criticism generally don’t do well in this line of work. Peer review forces us to critically examine our statements and sharpen our arguments. I was pleased and gratified to see some of the changes proposed for FNPS website and literature – why leave ‘low hanging fruit’ around for critics? While I didn’t appreciate some the comments made about me, if I’ve caused this group and others to strengthen their arguments and re-examine some of their assertions regarding natives, then the slings and arrows I’ve taken these past couple weeks haven’t been in vain.

Are natives the answer? Revisited

I started to leave a comment on Linda’s Friday post regarding Seattle Public Utilities proposed building codes regarding “Healthy Landscapes” but decided I’d weigh in with a regular post. Linda honed in on the 75% native requirement but there are lots of things to make one scratch their heads in the proposed codes.

Existing invasive plant species shall be removed and no invasive species planted.
No mention of how invasive plants shall be removed. Heavy-duty herbicides? Armies of school children forced into slave labor? Slow-moving ground-fire? Goats?

75% of all new plantings will be native to Western Washington.
So where did 75% come from? Sounds like a number that was pulled out of the air. How is 75% defined? 75% of plants? 75% of the area? And how does this foster “Healthy Landscapes”? If I have a 2 acre landscape and plant an acre and half of salal or Oregon grape I’ve met the requirement of 75% but have I increased species diversity or structural diversity or contributed to a “Healthy Landscape”?

A vegetation plan must be submitted for review.
By whom? What happens if they (whoever ‘they’ are) don’t like it?

Existing native plant species shall be protected whenever possible.
Sounds reasonable but what about existing non-invasive non-natives? Could a homeowner be required to cut down a 40-year-old red maple?

And on and on we could go. Let me state clearly, I’m not against native plants. Quite the opposite – I grew up in western Washington and have a passion for PNW plants since my high school days. Since moving to Michigan I’ve written articles and given talks promoting natives here as well. http://www.hrt.msu.edu/assets/PagePDFs/bert-cregg/GoingNative.pdf

Nonetheless, I think many in the native plant movement hurt their cause by parroting the same old lines without ever critically thinking about what they’re saying. Repeating a lie often enough times does not make it the truth.

Let’s critically look at some of the reasons for planting natives according to the Washington State Native Plant Society:

Native plants are adapted to our climate of wet winters and dry summers.
True. But so are lots of non-natives. Adaptedness is a function of the environment in which plants have evolved; whether it’s native or exotic. There are many climates around the world that are similar to the PNW and can produce similarly adapted plants.

Require less water than most non-natives once they are established.
Once again, adaptations such as drought tolerance are a function of the climate under which plants evolved. There are many exotic species that are more drought hardy than western Washington natives and likely to use less water.

Resist native pests and diseases better.
Sometimes. But unfortunately the days of worrying only about native pests are in the distant past. Exotic pests are here and they are here to stay. Dutch elm disease, white pine blister rust, emerald ash borer, chestnut blight, Japanese beetle, the list of exotic pests is long and getting longer. Native does not mean pest-free.

Improve water quality by needing less fertilizer and no pesticides.
OK, here’s where I get confused. The reasoning in Doug Tallamy’s book, Bringing Nature Home, is that native insects don’t feed on exotic plants, therefore if we plant exotics, native food pyramids will collapse and it will be the end of life as we know it. So… if native insects won’t feed on exotic plants, why would exotics require more pesticide use?

Save resources and encourage a sense of Stewardship.
Ok, now maybe we’re getting somewhere. Not sure why stewardship is capitalized here but if they mean a ‘sense of place’ or a ‘connection to the natural environment’ then I can buy it. Many native activists, including Tallamy, run away from this argument – apparently it doesn’t sound scientific enough – but it’s one of the best we have. Washington state has some of the most incredible plants anywhere. They should be celebrated and promoted and planted. In my mind, the biggest reason for planting natives – along with carefully selected non-natives – is to increase overall biodiversity. When I mention biodiversity I am speaking broadly; species diversity, structural diversity, age-class diversity, and landscape diversity. When we look to the future we have no idea what lies ahead. We don’t know what new, exotic diseases or insects are looming on the horizon. Most of us expect climate will change but no one can say with certainty how. Plants cannot evolve as fast as climate will change or as fast as new pest will be introduced. The only way to deal with this uncertainly is to spread the risk through diversity – this includes natives, exotics, and even interspecific hybrids.

Does native matter?

We’ve had lots of lively discussion on my post regarding the Mark Davis et al. comment in Nature on natives and exotics. I have been traveling and otherwise occupied and have not had a chance to comment so I feel a little like the kid that kicked the anthill and then ran away. Fortunately, Holly was gracious enough to forego her post today (I promise to return the favor, Holly!) so I can chime back in.

Obviously there are lots of layers to the debate but one of the main items in the discussion is whether there is an inherent ecological advantage in planting natives over exotics. At this point the focus always seems to shift to herbivory and the question of whether native insects will eat non-native plants. There are certainly examples each way; some insects are generalists while others are highly specific. More importantly, however, plants fill many other roles in the environment beyond serving as food for insects. Moreover, species composition is just one aspect of diversity. The ecological function of landscape is also determined by how we manage other factors such as structural diversity and age class distributions. In his book “Bringing Nature Home” Doug Tallamy shows a picture of a bland, sprawling suburban landscape ( p. 24) and notes “this highly simplified community is made up of a few species of alien ornamental plants that provide neither food nor shelter for wildlife.” OK, I’ll buy that. But would the situation change if the blue grass was changed to a native grass kept mowed to 2” and the two widely spaced shade trees were changed to natives? Doubtful. The structural complexity; that is, the number and arrangement of grasses, annuals, shrubs, and trees, is likely a bigger driver of ecosystem function than whether the plants are native or exotic.

In his thoughtful comments on the blog post Vincent Vizachero sums up, “I stand by my view that the general heuristic of favoring native plants over alien plants is better than the alternative of not caring about origin at all.” I can buy that as well, but with the caveat that other factors are equal. The rub, of course, is that other factors are rarely equal. And I suppose this is where the pragmatic approach discussed by Davis et al. resonates with me. In my position I do a lot of programming on trees for urban and community forests. I go through a list of criteria to consider for tree selection. Here are some of the key factors I usually discuss:

Adaptation There is no argument that there are well-documented environmental, economic and social benefits to trees in urban and suburban areas. But in order to fulfill these roles trees must be able to survive where they are planted. This means being adapted to abiotic and biotic environmental conditions which are often adverse. In this region of the country there are some native trees that fit the ‘tough trees for tough places’ bill, such as swamp white oak, bur oak, and honey locust. Many other natives, especially understory species, are much more difficult to site.

This street planting in Lansing alternated green ash and Norway maple.

Available space This seems like a no-brainer, but it’s amazing how often this gets overlooked and we end up with too much tree and too little space. Again, we have some great small native trees; Carpinus, redbud, striped maple. But these can be limited in their site adaptability.

Ash stumps

Diversity In Michigan some communities have lost 30% of their tree cover to the emerald ash borer. Have we learned our lesson about improving species diversity? Not really. But we need to keep trying. Exotic pests are here and here to stay. Does anyone believe that global trade will decrease in the near future? Does anyone believe that there will be quantum leap in our ability to detect and intercept hitch-hiking pests? In order to continue to accrue the benefits of urban and community forests we need to continue to diversify our portfolio; this includes a mix of natives and exotics. I doubt there will ever be sufficient data to prove one way other, but it seems reasonable to me that an urban and community forest balanced among 20-25 native and exotic species will be better able to withstand the slings and arrows of weather and pests better than one made up of 8-10 natives.

Excerpt from Davis et al. letter to Nature on natives vs aliens

In yesterday’s post I linked to a letter in Nature by Mark Davis and a number of other ecologists on the role and native and alien plants. Unfortunately the journal requires a subscription. Copyright laws prevent me from re-printing the entire article, however, below is an excerpt from the conclusion, which I think captures most of their message.

“Most human and natural communities now consist both of long-term residents and of new arrivals, and ecosystems are emerging that never existed before. It is impractical to try to restore ecosystems to some ‘rightful’ historical state. For example, of the 30 planned plant eradication efforts undertaken in the Galapagos Islands since 1996, only 4 have been successful. We must embrace the fact of ‘novel ecosystems’ and incorporate many alien species into management plans, rather than try to achieve the often impossible goal of eradicating them or drastically reducing their abundance. Indeed, many of the species that people think of as native are actually alien. For instance, in the United States, the ring-necked pheasant, the state bird of South Dakota, is not native to the great plains of North America but was introduced from Asia as a game bird in the latter half of the nineteenth century.

“Specifically, policy and management decisions must take into account the positive effects of many invaders. During the 1990s, the US Department of Agriculture (USDA) declared several species of introduced honeysuckles to be alien (harmful), and banned their sale in more than 25 states. Ironically, from the 1960s to the 1980s, the USDA had introduced many of these same species in land reclamation projects, and to improve bird habitats. Recent data suggest that the agency’s initial instincts may have been appropriate. In Pennsylvania, more non-native honeysuckles mean more native bird species. Also the seed dispersal of native berry-producing plants is higher in places where non-native honeysuckles are most abundant (Gleditsch, J. M. & Carlo, T. J. Diversity Distrib. 17, 244-253 (2010).

“Clearly, natural-resource agencies and organizations should base their management plans on sound empirical evidence and not on unfounded claims of harm caused by non-natives. Another valuable step would be for scientists and professionals in conservation to convey to the public that many alien species are useful.

“We are not suggesting that conservationists abandon their efforts to mitigate serious problems caused by some introduced species, or that governments should stop trying to prevent potentially harmful species from entering their countries. But we urge conservationists and land managers to organize priorities around whether species are producing benefits or harm to biodiversity, human health, ecological services and economies. Nearly two centuries on from the introduction of the concept of nativeness, it is time for conservationists to focus much more on the functions of species, and much less on where they originated.”

Ecologists weigh in on native-exotic debate

Charlie Rohwer, a frequent guest contributor to the Garden Professors, brought to my attention a recent letter in Nature by Mark Davis and 18 other ecologist entitled, “Don’t judge species on their origins.” Davis is a leading authority on invasive species and author the book Invasion Biology. In their article, Davis and his co-authors make many of the same points that I’ve made here on the blog (Are natives the answer? Dec. 14, 2009; Restoration ecologists you need us – part 2. Aug. 9, 2010) regarding the native/exotic debate. The main point is that we need to develop a more pragmatic approach to managing landscape systems and this includes natives and exotic species; it’s not an either/or question anymore, not that it ever really was.

A couple of excerpts from their letter:

“It is time for scientists, land managers and policy-makers to ditch this preoccupation with the native–alien dichotomy and embrace more dynamic and pragmatic approaches to the conservation and management of species — approaches better suited to our fast-changing planet.”

The pragmatic approach that Davis and his co-authors (and I) advocate recognizes a several realities:

Exotics can fill many of the same ecological roles and niches as natives, Doug Talamy’s book notwithstanding.

Any inherent “ecological superiority” of natives over exotics has long since been negated by anthropogenic land-use change, alien pests, and climate change.

Attempts to eradicate alien species are largely warm-fuzzy exercises with little likelihood of success without liberal use of industrial-strength herbicides.

Creating a sense of place

As many GP readers know I’m originally from Olympia, WA. Once a week or so I troll through the on-line version of my hometown newspaper, the Daily Olympian (“the Daily ‘O’” for short or, more commonly, “the Daily Zero”) to keep up with latest happenings back home and to see if any of my high school classmates are on their way to jail. While none of the Olympia High Class of ’78 made the news recently, my interest was piqued the other day by the headline “Saving the world – from weeds”. The article described the Earth day efforts of local grade-schoolers to eradicate Scotch broom from a local nature trail.

http://www.theolympian.com/2011/04/23/1626461/saving-the-world-from-weeds.html#storylink=misearch

For those that are not familiar, Scotch broom is an exotic shrub that commonly invades disturbed areas throughout the Northwest. It’s been a problem for years and, even as a kid 40 years ago, I remember every cutbank around town covered with the nasty yellow blossoms. In doing a little trolling on the internet I was surprised (stunned is probably a better word) to learn that there are parts of the country where Scotch broom is still sold as an ornamental shrub – named cultivars and all. There are commercial cultivars of dandelion after all, so why not?

As we’ve noted here on the GP blog, there are lots of layers of complexity to the native/non-native discussion. In many cases I think native advocates have over-sold the ecological side to the argument. But the Daily O article got my dander up; not because 4^th graders were pulling up Scotch broom – good riddance and keep up the good work kids – but because the Scotch broom was replaced with trees and shrubs that were all exotics in that part of the Northwest.

Native plant advocates often downplay the ‘sense of place’ argument in promoting natives. I suppose they feel the ecological arguments are based on ‘harder science’ and therefore more convincing. While it can be argued that native plants have adapted to the environment in which they evolved; it’s not always a given that the native conditions still exists, particularly in the built environment. What’s beyond argument, however, is that trees and other plants provide a connection to the natural world around us and, for lack of a better term, do give us a sense of place. From my personal experience, I have a visceral reaction to the sight of Scotch broom or English ivy in the Northwest where I’m native. Here in Michigan, on the other hand, I’m less bothered by exotics – even some that may be considered invasive. I suspect many native-born Michiganders have the opposite reaction.

I’m sure part of my connection to all things Washington stems from lessons learned in school (I still know all the lyrics to ‘Washington my Home’ and my plant collection form Mr. Chance’s high school Botany class is still somewhere in the attic of my parent’s house). Which is why I was flummoxed by the schoolkids planting tulip poplars and sequoias instead of big leaf maples and western redcedars. Wouldn’t this exercise have been a great opportunity to teach these young people about the great trees and shrubs that are native to the Northwest and to give these kids a sense of place?