Which Black Eyed Susan is Which? 

Do you want a black eye? Black eyed Susan, that is. Or is that a brown eyed Susan? The other day someone asked me how to differentiate this group of plants that, at first glance, look so much alike. Today, I will attempt to tackle that question here. 

Those who know me know that I get really frustrated with common names for plants. Depending on where you live, the name black eyed Susan is used for a number of different yellow flowers with a dark center. The most common ones, at least here in southern Ontario, are Rudbeckia hirta (which I call black eyed Susan), Rudbeckia triloba (brown eyed Susan) and Rudbeckia fulgida (orange coneflower). However, these plants also come with a lot of other names that you might know them by, just to keep things confusing. For example: 

Rudbeckia hirta (Black Eyed Susan) is also called Bristly Coneflower, Brown Betty, Brown-eyed Susan, Common Black-eyed Susan, English Bull’s Eye, Gloriosa Daisy, Golden Jerusalem, Poor-land Daisy, Yellow Daisy and Yellow Ox-eye Daisy. 

Rudbeckia fulgida (Orange Coneflower) is also known as Black Eyed Susan, Brilliant Coneflower, Brown Eyed Susan, Orange Rudbeckia, Perennial Black-eyed Susan, Showy Black-eyed Susan and Showy Coneflower. 

Rudbeckia triloba (Brown Eyed Susan) also goes by the names Thin-leaved Coneflower, Three-lobed Coneflower and Three-lobed Rudbeckia. 

But it’s not just the names that can be confusing. To the uninitiated, these 3 flowers look very similar. And the descriptions you read about them don’t always help, simply because there can be so much variability within each species that, until you get to know the plants, the descriptions seem to overlap. 

Rudbeckia hirta – Black Eyed Susan 

Let’s start with Rudbeckia hirta, Black Eyed Susan. For me, the main differentiating characteristic is the fuzzy leaves and stems – fuzzy enough that the leaves actually appear to be a lighter colour than the other Rudbeckias. But fuzziness is a relative characteristic as all 3 have a certain amount of hairiness to the leaves and stems. Once you see the leaves side by side, however, you will easily tell them apart in the future (most of the time).  

R. hirta leaves tend to be strap-like and, on average, tend to be longer and narrower than the other two. And they are ALMOST ALWAYS very hairy. 

This plant is quite variable in its nature, though. It may be an annual, a biennial or even a short-lived perennial in some cases. And the genetic variability within the species can result in individuals with different petal shapes, different leaf shapes and sizes, and even a range of hairiness of the stem and leaves. But on average, the leaves and stems have a pale fuzzy appearance. If it’s late in the season, they also tend to die off in early fall (at least the annual and biennial ones do) whereas R. fulgida and R. triloba tend to stay green well into the late fall, even after the flowers have finished. 

Rudbeckia hirta does well in full sun to part shade in just about any dry to moist, reasonably fertile, well-drained soil. This plant will grow to a little over 3’ tall and in the wild is found in fields, open woods and along roadsides. 

R. hirta Native Range: 

Rudbeckia fulgida – Orange Coneflower 

This shorter statured plant is an extremely popular garden perennial, mainly because once it starts blooming it tends to put on a non-stop show for months. In most years in my southwestern Ontario garden, it starts to flower in late June or early July and keeps going till frost – sometimes as late as November, though after the drought we had here this year, they’ve pretty much finished blooming in mid-September. 

A very common cultivar (or nativar, if you prefer) is Goldsturm. There are also even shorter cultivars, usually with the word “Little” somewhere in the name. The straight species typically grows 2-3’ tall, as does the Goldsturm variety. Most of the others are only 1-2’ tall. I have yet to find a definitive article on how Goldsturm is different from the true species. If you have the scoop on this, please let me know. 

The leaves on R. fulgida tend to be much wider than on R. hirta and usually have fairly large serrations along the edges, especially on the lower leaves. As you can see in the photos, though, they may have no serrations at all. And though they may feel somewhat rough and hairy, they are not nearly as hairy (on average) as R. hirta. 

One thing is for sure – R. fulgida produces a much denser mass of colour than R. hirta, and for a much longer period of time, though R. hirta always starts flowering a couple of weeks before this one does. It’s not that fussy about where it grows – it will do well in moist to dry, sandy to clay soils in full sun to part shade. I have a patch that is in full, light shade and it is doing just fine.  

R. fulgida Native Range: 

Rubeckia triloba – Brown Eyed Susan 

Not native in Ontario, this nonetheless very popular short-lived (typically 2-3 years) perennial is the tallest of the 3 plants discussed here – in ideal conditions (full sun, moist loamy soil) it can get upwards of 5’ in height, though one writer indicated his plant hit 8’ tall!  

The easiest way to differentiate R. triloba from the other two is to take a look at the leaves near the base of the plant. These are what give this plant its specific epithet (or species name) – triloba. The lower leaves have 3 (occasionally 2) lobes, as seen in the accompanying photo. The upper leaves look quite similar to R. fulgida, with the same variability in hairiness and serrations.  

The other telltale difference is that R. triloba also tends to have a fairly reddish stem – sometimes it may be a deep solid burgundy colour, but on other plants it may be more of a striped stem. The stems are almost always fairly hairy.  

Rudbeckia triloba is probably the fussiest of the 3 for growing conditions, but it is still quite versatile. It prefers moist to mesic loamy or sandy-loam soils, though some clay is tolerated. Like Rudbeckia fulgida, it blooms from July to first frost. 

R. triloba Native Range: 

If you have a native plant gardening related topic that you would like to know more about, let me know and I will add it to my growing list (pun intended). If it’s something I get multiple requests for, or is simply something that strikes my fancy, it will surely move up the priority list. 

Happy Native Plant Gardening.  

Many of is remember the old nursery rhyme Mary, Mary, quite contrary, How does your garden grow?

Although historians disagree on the possible political meanings behind this 18th century English nursery rhyme, I wish to use this question “How does your garden grow” to explore the various approaches to gardening with native plants.

Naturalized Gardens

We all garden with native plants for different reasons. Some gardeners attempt to create a more ‘natural’ habitat for insects, birds and other wildlife on their property and design their gardens around ecological principles. These gardens may often appear messy to the uninitiated, and are often more suited to larger properties and/or rural properties. Otherwise, they may fall afoul of local city ordinances that were often developed in the 60s and 70s when uniform, mowed grass was seen as desirable and when bylaws were enacted to prevent homeowners from simply neglecting their yards.

Formal Gardens

At the other end of the spectrum are those who have taken the formal flower beds of European ancestry and simply replaced some or all of the non-native species with native ones. These gardens are often geared to human sensibilities and historical tastes. The fact they attract more insect life than gardens comprised solely of exotic species is more a lucky side effect than a planned outcome.

And then there is the whole gamut of garden design options between the two extremes.

Semi Formal

The Importance of Native Plants

I would be willing to bet that most of us grow native plants, at least in part, for the benefit they provide to our wildlife. To that end, ANY incorporation of native species is likely to be better than none at all. However, Doug Tallamy’s research in the US has shown that the successful fledging of a nest of Carolina chickadees requires at least 70% native species within their foraging range. And anything below 30% will likely result in the complete loss of the nest of babies. This is because non-native plants do not host the diversity and numbers of insects necessary to feed a nestful of baby birds. Although Tallamy’s research looked at just the one bird species, it is probably safe to assume that it is similar for other bird species, since most birds – even the seed eaters – raise their young on a diet of caterpillars, spiders and other soft-bodied insects. (If you haven’t read them yet, I highly recommend Tallamy’s books Bringing Nature Home and Nature’s Best Hope.)

If you’re reading this article, then you are most likely already aware of the importance of native plants. But how many others are? You would hope that anyone who gardens would have an appreciation for nature. And even though native plant gardening is the fastest growing (pun intended) sector of horticulture in North America, a lot of gardeners are still unaware of its virtues.

Take for example a recent trip I made to a scenic small town in southern Ontario, noted for its active horticulture society and its beautiful gardens. In a 10 block walk, I saw one yard containing a native species in its flower beds. Note the singular. And technically, the town was a bit far north to actually claim Rudbeckia fulgida (orange coneflower) as a native species. (To be fair, in another part of town I did find a couple of gardens that were primarily natives, but that was it.) We have a long way to go to educate other gardeners on the benefits (and beauty) that adding native plants can provide.

Where Do I Start?

But if we want to grow natives, which way is best? Well, that depends. My own gardens fall somewhere closer to the ‘formal flower beds’ end of the spectrum, designed to be showcases of what we can do with native species. Though with the passage of time they are slowly moving away from that as I let plants spread and self-seed, often where they want.

I came at my gardens from the perspective of an educator wanting to show folks that native plants can be just as beautiful, and usually a lot more beneficial, than non-native species. My aim has been to bring those who knew only the Edwardian style of manicured gardens full of exotic plants into the world of native plant gardening.

In the municipality of Chatham-Kent (in southwestern Ontario) we recently held our second annual native plants garden tour. (Thanks and a shout out to Mike Smith with ReLeaf Chatham-Kent for spearheading this). This year, gardens once again ranged from restored acreages to small butterfly gardens, from gardens planted in a cul-de-sac island by a committee to a half acre of formal flower beds of only native species set in a private garden. Some have natives mixed with non-natives while other “purists” try to plant only what was found locally (or nearby) before Europeans arrived. Some have been growing natives for a decade or more; for others this is their first venture into growing indigenous species.

If you’re reading this, then at least you are interested in growing native plants. And if you haven’t started yet, don’t worry – it’s easy. But it will take some thought and some homework. First you need to decide WHY you want to grow native plants. That will help you choose the style that will work best for you.

Do you have already established garden beds? Perhaps you just bought your first house and have inherited a lot of non-native and possibly some invasive species. Do you like the layout of the gardens, or do you have a vision of your own? Start by identifying the non-natives that are invasive or otherwise problematic and digging those out. There are lots of on-line resources to help with this. Just Google “invasive plants” and your state or province. Or look up a document called “Plant me Instead”. Visit some native plant nurseries (this web site has a map of all the native plant sources in North America that I’ve been able to find), attend a webinar by your local naturalist organization, join a native plant gardening Facebook group (if you haven’t already). These are all great ways to learn about what is or isn’t native and to help you decide what to plant where.

Do you have a large, blank slate? This can sometimes be very intimidating. And unless you’ve got very deep pockets, you probably won’t want to convert the whole yard at once. But don’t just jump in with both feet. Even if you’ve been growing natives for a while, if this is a new location then watch the sun – where is it sunny the longest? Where is the shade? What is your soil type? (If you don’t know, get it tested. Your local department of Agriculture will be able to tell you where, and how much it will cost. Or you can buy a soil test kit from a number of sources, and though these won’t be quite as accurate as an official laboratory test, they may be good enough to get you started.) Is the soil dry? Are there low areas that might stay wet for part of the year or after a heavy rain? If all else fails, there are lots of knowledgeable folks living probably not far from you, and some of these will be happy to come and advise you (for a fee).

Water is Important,Too!

If your intention is to attract birds, dragonflies and other creatures, try to add moving water – either a small waterfalls or simply a fountain. The sound of running water will attract birds from far and wide, and you’ll see a huge increase in insects like dragonflies and damselflies, all of which will come to bathe and to drink.

There is no prescription for native plant gardening. We all grow what we grow for our own reasons. One thing everybody growing native plants seems to agree on, though – we wonder why everyone isn’t on board yet.

Happy native plant gardening.

The native plant gardening world is full of terminology that those gardening with non-natives have seldom had to consider. In this month’s article, I hope to shed some light on what some of these terms actually mean so that you can speak confidently and knowledgeably with garden center staff and fellow gardeners. 

Native vs Naturalized 

I started my journey into native plant gardening with the purchase of a package of “wildflower” seeds. When I recognized California poppies, bachelor’s buttons, and a few others I knew were not from these parts, I became confused. That’s when I discovered that wildflower is NOT the same as native. After a little more research, and a broken heart, I discovered that many of the wild plants I grew up loving in the fields and forests were actually European, Asian or other non-natives that had escaped from gardens over the past couple of hundred years and not the cherished native plants I thought they were. So what IS a native plant? 

In its simplest terms, the general consensus used by many but not all, is that any plants growing in an area before the European settlers arrived are considered native. These are the plants that evolved here and developed ecological relationships with the insects and birds and other animals as well as with the surrounding plants. These relationships developed over thousands of years. Europeans, as well as those from other parts of the world, came to this continent and brought plants they were used to using and or seeing, and all of these plants are considered to be non-native. Yes, plants migrate, but they do so very slowly and local ecosystems typically have time to react to any newcomers. The sheer volume and strangeness of the plants that were introduced by settlers really disrupted these natural changes. And, yes, changing climate is likely to allow plants not previously growing here to survive, but the rate of change will be nothing like the speed of putting a packet of seed in a truck in Arkansas and spreading in your southern Ontario garden a week later. 

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I don’t know when the currently accepted definition was proposed or by whom, and it leaves many unanswered questions, such as: should plants that were brought here by First Nations peoples (e.g. pawpaw – Asimina triloba) also be considered native? By keeping the definition simple, i.e. is it pre-European, the answer is also simple: yes. (There have been many long, philosophical discussions on the topic in many native plant forums. But I like to keep things as simple so this is the definition I use.) 

So what, then, is a naturalized plant? Naturalized simply means that that particular non-native species can exist in the wild without human intervention. Many of my favourite childhood wildflowers, like mullein (Verbascum Thapsus) and common chicory (Cichorium intybus), and even dandelions (Taraxacum officinale) fall into this category. Though many non-natives have adapted well to the wild, many, like zinnias (Zinnia elegans), petunias (Petunia spp.) and many of our vegetable crops, like bell peppers (Capsicum annuum), cannot survive long in our region without human intervention. Some, on the other hand, have adapted so well they are considered invasive. 

Invasive vs Aggressive 

We often hear about invasive species, and sometimes (incorrectly) an overly aggressive native plant like Jerusalem artichoke (Helianthus tuberosus), or Canada goldenrod (Solidago canadensis) are called invasive. However, the term invasive species is reserved for non-native plants that are so prolific, either because they self seed, spread vegetatively, and/or produce toxins to inhibit the growth of any competition, that they spread unchecked and have a large negative impact on the natural ecological balance of an area. Note that not all non-native species are invasive, but those that are can have devastating effects on local flora and fauna.  

They way I wrapped my head around the terminology is with an analogy: If our military forces came into a major city and started roughing up and arresting people, we’d say they are being aggressive, but if a foreign army did this, we’d say they were invading. The domestic army can’t invade because it’s already here. Same for plants – Canada goldenrod can’t be invasive because it belongs here. But a plant from another part of North America that was never here before CAN be considered invasive. For instance, cup plant (Silphium perfoliatum) was never native in New York state but it is a very aggressive spreader and is therefore considered an invasive species there^{1, 2} (and it is illegal to sell or grow it for sale in that state).   

Weeds 

Weed is another term that has some confusion surrounding it (I’m not talking about the weed your brother-in-law smokes, either). Weeds may be non-native OR native plants. We’re all familiar with dandelions – some consider it a weed while others do not. This Eurasian-native species was brought by European settlers as early as the 1600s as a food and medicine plant³. Plants like Canada thistle (despite its name, it, too, comes from Eurasia) were brought for the same reasons, or because they were familiar flower garden plants “back home”. These, and many more, have become ubiquitous throughout North America.  But the term weed is actually an agricultural term and describes any plant that has a negative economic impact on agricultural (food) production. In our gardens, is simply a plant that is unwanted where it is growing and in traditional gardening, these often happen to be native species, though not always.  

Erigeron canadensis (Horseweed, or Canada Fleabane) is a prime example of a native plant that is considered a serious weed in agricultural crops, especially since it developed resistance to glyphosate (the major weed-killing ingredient in Roundup) and to acetolactate synthase (ALS) herbicides. Milkweed, especially Asclepias syriaca or common milkweed, was long considered a noxious weed – a special category for the really nasty ones – and was eliminated from farm fields whenever it was encountered. Livestock won’t eat it, its rapidly spreading rhizomes enables it to take over large areas of a field out-competing the farm crops, and it had huge impacts on the farmer’s bottom line. We now know that it is also essential for the survival of the monarch butterfly, and as a result many jurisdictions have removed it from their noxious weeds lists. 

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Essentially, a weed is simply a plant growing where you don’t want it. In my all-native-plants garden, for instance, I consider squirrel-planted tulips and star of Bethlehem plants to be weeds. (I even refer to my hosta bed under a large maple tree in my front yard as my “weed garden”, and one day it will get “weeded” and native plants put in). 

Cultivars and Nativars 

Some other terms in native plant gardening also bring some confusion, especially to those just starting out. For instance, what’s the deal with cultivars and what is a nativar? The term cultivar is simply an abbreviation for the phrase “cultivated variety”. Nativar is a newer term that has come with the surging interest in native plant gardening and is simply a combination of two terms, native and cultivar.  

When many of us start to grow native plants in our gardens, we bring with us a history of growing non-natives. We, therefore, often look to the exotics for unusual colours or forms. I was no different in this regard – I was in in my 50s, with close to 40 years gardening experience, when I discovered native plant gardening.  When I saw a cardinal flower (Lobelia cardinalis) with a deep burgundy colour, a swamp milkweed (Asclepias incarnata) with a pure white flower, or a bloodroot (Sanguinaria canadensis) with a “double” flower, I was amazed and wanted it in my garden. Most often these plants are simply natural mutations that horticulturalists have latched onto and have cloned for resale. Some will breed true to the new form, but some are one-off freaks of nature whose seeds, if they even produce any, will revert to the original. Others are the result of selective breeding. And because the horticulture trade is, for the most part, driven by profit, some growers will select for unusual colours or forms to meet the demand for exotic plants.  

You can usually spot a plant in the garden center that is a cultivar because the tradition is to include the commercial name (either in quotation marks or not) after the scientific name, such as Aclepias incarnata “Ice Ballet” – note that the scientific name is in italics but the cultivar name is not. The use of var. (for variety, or in Latin, varietas) in the name, as in Cercis canadensis var. alba, is supposed to be used for naturally occurring varieties that have been selected for certain characteristics (in this case, a white version of redbud) rather than for plants that have been specifically bred for the trait. Unfortunately, there is not a lot of consistency in how these terms are used in the trade. (See article #4 in the reference list below for some more detailed explanations of these and other related terms.) 

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But as intriguing as some of these unusual variations are, recent research is showing that not all cultivars/nativars are equally valuable to the insects that depend on them⁵. Nutritional values can vary because the genetics that produce a desirable feature may be connected to those that impact nutritional value (similar to the genetics that make a German shepherd dog look the way it does also makes it susceptible to hip dysplasia). For instance, many of the double flowered nativars either do not produce nectar or pollen – the extra petals in double flowered species is often a mutation where the stamens in a flower are replaced by petals – and are often sterile, while others may be unpalatable to the insects that need it to survive. As the interest in native gardening grows so, apparently, does our interest in nativars and ongoing research is needed to determine which varieties are just as good for the insects as the originals.  

Summary 

You should now be able to confidently explain that, no, Canada goldenrod is NOT invasive, but garlic mustard is (and why). You should also be able to explain to your neighbour why those tulips in your lawn are actually weeds, why the milkweed in your front garden isn’t, and what the difference is. And finally, when shopping for some new plants, if you see a non-Latin name pinned to the end of the scientific name on the plant tag, you’ll know this is (most likely) not a pure native species and, as such, may not have the same value to the insects and other critters that need it to survive.  

Happy native-plant gardening. 

1. https://nyis.info/wp-content/uploads/2018/01/d8be1_Silphium.perforatum.NYS_.pdf  

2. https://www.dec.ny.gov/docs/lands_forests_pdf/isprohibitedplants2.pdf  

3. https://www.fbn.com/en-ca/community/blog/where-did-all-of-these-weeds-come-from 

4. https://www.mapleleavesforever.ca/cultivar-variety-or-nativar-as-it-relates-to-our-native-maple-species/ 

5. https://piedmontmastergardeners.org/article/native-species-or-cultivars-of-native-plants-does-it-matter/  

Most gardeners are familiar with the Plant Hardiness Zone (PHZ) maps that are found in many seed catalogues and garden centers, and with the paired numbering system (2a, 2b, 3a, 3b) etc. found on plant labels.  But what do these numbers really mean? How did they come about? And are they really relevant for native plant gardeners? 

The earliest PHZs were delineated in the 1920s by the Arnold Arboretum at Harvard University. In the 1960s, the US Department of Agriculture (USDA) devised their own set of PHZs using different criteria resulting in two different maps. However, the Arnold Arboretum map remained the standard until 1990, when the USDA, in conjunction with the US National Arboretum, and using data from thousands of weather stations, created the maps we now see. These maps are based on the average minimum winter temperatures. Each zone is marked at 10°F intervals, with the division between a and b at the 5° interval (e.g. zone 6a has an average winter minimum temperature of -10 to -5°F, 6b is -5 to 0°F). The logic behind this system is that plants have a cold threshold they won’t survive beyond.  

USDA PHZ: https://planthardiness.ars.usda.gov 

Unfortunately, these zones are a bit too simplified because plants are affected by more than just minimum winter temperatures, especially the further south you go. In snowbelt areas, for example, temperatures may drop well below freezing, but a deep blanket of snow can keep the plants safe. Basing the plant hardiness zone on minimum temperature doesn’t always work. Regardless of what minimum winter temperatures the plants will succumb to, some plants also tolerate heat much better than others. So the American Horticultural Society (AHS) devised their Plant Heat Zones based on the number of days the temperature went above 30°C (86°F), but their methodology created some problems as well. For instance, some plants can take lots of heat in the daytime but need cooler nights to recover and so just counting the number of days the temperature is above 30°C doesn’t really work. Also, plants like hostas love the heat, but they need cool winter temperature in order to go dormant so that they can start to grow again in the spring.  

AHS Heat Zone Map: https://ucanr.edu/blogs/dirt//blogfiles/37486_original.jpg 

If you’ve ever looked at the Canadian PHZ map, you’ve perhaps noticed that it doesn’t quite align with the USDA map. This is because the Canadian map is likely more properly called a Plant Suitability Map (though it still goes by the Plant Hardiness Zone moniker).  

Canadian PHZ: http://planthardiness.gc.ca/?m=1 

Originally developed in the 1960s, it uses a wide range of variables, not just minimum and or maximum temperature. The variables are: monthly mean of the daily minimum temperatures (°C) of the coldest month; mean frost free period above 0°C in days; amount of rainfall from June to November, inclusive; monthly mean of the daily maximum temperatures (°C) of the warmest month; winter factor expressed in terms of (0°C – X₁)Rjan where Rjan represents the rainfall in January expressed in mm; mean maximum snow depth; and maximum wind gust in (km/hr) in 30 years; and it incorporates them into a complex mathematical formula. You can read more about the formula and how it works here.

The original formula is the result of statistical analysis of the survival of 174 different trees and shrubs from 108 locations across the country (McKenney and Campbell, 2002, Getting into the Zone – what does Canada’s new plant hardiness zones map really mean? Frontline Technical Note #103 – see link to the paper at the end of this article). The newest version of the map was generated using computer models and interpolating climate data generated at more than 3400 locations across the country.  

Which is the best (i.e. most accurate and reliable) system? Being Canadian, I’m probably biased. But it would seem that the more thorough and complex Canadian system is likely the more accurate. The challenge is getting everyone to agree on one system. Most garden centers use the USDA system, probably because it has been around for a long time and the plant labels they purchase (likely from US sources even here in Canada) use that system.  

Surprisingly, even though the American and Canadian calculations are very different, in the southern Great Lakes region the results are close enough to be compatible for most of the plants – although some sources I’ve seen suggest that the Canadian and American systems may differ by as much as one complete zone in some locations. Also, both the US and Canada have been widely mapped using the USDA PHZ criteria, but I’ve not found any maps yet where the US has been mapped using the Canadian system. So, it doesn’t look like we’ll have a unified system any time soon. 

USDA Plant Hardiness Zone Map (North America): http://www.perennials.com/content/plant-hardiness-zone-maps/

But even with all the variables used in the Canadian maps, there are so many things that will affect the plant’s survivability that just cannot be easily mapped. Extreme weather events, microclimates caused by built structures, local topography, even mulching and watering, can have a significant impact on plant survival. 

When it comes to native plants, though, a lot of research is still needed to verify the zones they will survive. Accurate range maps overlaid on PHZ maps will go a long way to answer these questions, but native range of so many of our native plants have not been mapped with any level of detail.  

Then there is the question of whether we should even worry about what areas our native plants are capable of growing in – if the idea is to keep native plants in their native range, the more important issue is to figure out where the plants actually grew before we started putting them in our gardens everywhere. This way our native plant gardening efforts will better serve the insects and animals the plants evolved with, and not just our personal aesthetic.  

Until next time, happy native plant gardening. 

Rick 

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