Let Leaf Arrangement Lead the Way

 

Viburnum showing opposite arrangement

 

There are people who find plant identification intimidating. It might be you. Don’t let it be that way; use just a little bit of logic to quickly get you on the right path. Recently a photo was submitted to a plant identification group and the person said that a plant app had indicated it might be black cherry (Prunus serotina). Plant id apps are only as good as the photo submitted; they can’t always see the leaf arrangement and other important details from photos, so you’ll always want to double check their guesses.

With a closer look at this person's photo (not included here), one could discern that the leaves were oppositely arranged on the stem. Since black cherry has alternate leaves, it could not be that. When I talk to people about plant identification, leaf arrangement is my number one tip. I’ve written about this before, but the message can always be repeated (my previous blog is linked here and still worth reading with examples of woody plants).

While this concept is most persistent in woody plants (you can see the arrangement of tree and shrub branches in the winter), it also applies to herbaceous perennials. Herbaceous plants with well-known opposite leaf arrangement include plants in the mint family (Lamiaceae), but there are others like beardtongues (Penstemon), sunflowers (Helianthus), boneset (Eupatorium), Phlox, milkweed (Asclepias), and St. John’s wort (Hypericum). 

Opposite leaf arrangement

Alternate leaf arrangement

Leaf arrangement is visible in the first true leaves produced by dicot seedlings; dicots produce a pair of cotyledon leaves that often don't resemble the plants "true" leaves. For example, when they pop up in the spring, a maple (opposite) clearly has two true leaves compared to alternately arranged plants which produce only one. These cotyledon leaves are often very plain (although American basswood has fancy cotyledon leaves). Here are two examples:

Maple seedling with two plain cotyledon and two true 
leaves (example of opposite from Strand Herbarium)

Basswood seedling with two fancy cotyledon and
one true leaf (example of alternate)

While identifying the leaf arrangement can get you further on your plant identification path, it is not the only clue and you should consider other aspects of the plant. In particular, there are two cautions to consider:

• A leaf or branch may be missing due to damage, causing an oppositely-arranged plant to look like it has alternate arrangement. Check more than one place on the plant.
• Some herbaceous plants (that is, not woody) with opposite arrangement may transition to alternate arrangement toward the top of the flowering stem.

As in my earlier post, I encourage you to practice this skill on plants that you already know to see if you get the right identification. Put this concept at the top of your toolbox and see where it takes you!

Keystone Plants Maximize Small Spaces

Yards are getting smaller and the conversion of natural habitat to residential communities is shrinking the availability of native plants to support native insects. While we should protect native habitat as our first choice for supporting native insects, we have learned that we can make a difference in our designed landscapes by choosing the most productive plants. 

“Keystone” is the term for the most productive plants in terms of how much they support insect herbivores such as caterpillars, the larval form of butterflies, moths, and sawflies. The more insects a plant can support, the more productive it can be for the local ecosystem that depends on those insects (like birds).

Native Clematis

It’s too hot and dry to plant now, but you might be thinking of what you’ll buy and plant in the fall so now is a good time to make a list. Including some keystone plants would help you take your efforts further than without them. 

I had a hard time finding a good list so I created one using Doug Tallamy’s early resources. You can download and print my list from here. Of course you’ll want to first take stock of what you might already have – for example you might already have an oak tree or a maple (or if your neighbor has those, you can usually consider them close enough to count). If so, plant for maximum diversity by choosing something new like a river birch, a willow, or a hawthorn.

If you have very little space, you might consider choosing keystone herbaceous plants (these are your perennials, see the back side of my handout for them). Homegrown National Park has some nice resources for using keystone plants in containers; here is a link to the Southeastern one. You’ll notice them using the keystone plants goldenrod, asters, and sunflowers – those are the top 3 keystone perennials. I've included links to earlier blogs about those 3 plants so you can see some of the choices available.

So walk around and see what you've got and make plans for adding new ones in the fall to amp up the biodiversity in your garden and in the ecosystem.

July 2024 Moment in Nature

It has been so very dry here the last month or so and quite hot as well. I have been watering my pots and some of the actively blooming in-ground perennials to help the insects that need those flowers.

One night it finally rained a lot and I walked outside to see how the plants were recovering. As I walked through the front, I spied this small frog (identified by a friend as a Spring Peeper) enjoying a moist leaf on the wingstem (Verbesina alternifolia). It seemed like a good sign and a much needed refresh for this month's #momentinnature.

Spring peeper

I found another couple of them later in the week in the backyard, so here's another photo showing the distinctive marking on the back (kind of an X).

Spring peeper

Do Native Pollinators Prefer Exotic Plants?

Certainly this is not a new question but a recent comment by someone about pollinators seeming to like - even prefer - the flowers of naturalized exotic plants made me go looking for information, specifically about native pollinators.

Tiger swallowtail on Tithonia

I do think that we have to establish first that native insects are dealing with an altered landscape; non-native flowers have only been here about 400-500 years, a blip in evolutionary time as far as insects are concerned. Second, as a result of some naturalized plants (like Queen Anne’s lace, an exotic species that is related to a native but less common species called wild carrot), the abundance of exotic weeds may have now almost replaced whichever native plants would have been present, leaving native insects little choice but to use exotics. Third, we should recognize that pollinator preferences for certain flower types (short vs. long floral tubes, for example), will affect what plants they can use and if they can adapt.

We know from publications like this one from The Xerces Society that eco-regionally appropriate native plants give us the best diversity of native pollinators. That is, a diversity of native plants brings us a bigger mix of native bees, butterflies, flies, beetles, wasps - including specialists. We should use native plants from our same ecoregion (e.g., Piedmont, Coastal Plain, etc.) to ensure we support pollinators of the same area. 

Specialist bee: Southeastern blueberry bee

What can we expect when native pollinators live in areas of more exotic than native plants vs. when they have appropriate native plants in more abundance: do they prefer the newer plants (exotic) or do they prefer the indigenous plants?

Research published in 2020 by folks in the Department of Entomology at Cornell University found that native pollinators do prefer native plants when available: “Honey bees visited introduced and native plants at similar rates regardless of floral abundance. In contrast, as floral abundance increased, wild pollinator visitation rate decreased more strongly for introduced plants than native plants.” That is, when native pollinators have access to more native flowering plants, they prefer the native ones.  

Another study published in 2020 based on research in 2016 and 2017 in Maryland, found similar results. The authors feel that exotic plants in pollinator mixes may help pollinators in early spring for generalist insects, but "non-native plants also alter the composition of plant communities, may not support as many specialist bees, and appear to affect individual and network specialization of bee communities with unknown consequences for plants and bees." More study is needed, they conclude.  

Certainly pollinators are using what plants are available and, increasingly, those plants are exotic ones. But don't be fooled that this helps native pollinators overall. Some pollinators - the specialists - may be quietly disappearing if the native plants they need are no longer available.

While exotic and naturalized flowers may provide floral benefits to some native pollinators, the better human strategy is to continue to add regionally appropriate native plants back to degraded and residential areas to support native pollinators, particularly specialist ones.

Mountain mint is powerhouse native for pollinators