Lessons from Leuvehoofd

It was cool gray June day when I hopped off the train in Rotterdam. I was in the Netherlands for a soilless substrate conference in Leiden, almost ten years ago now. While there, I took the time to explore local gardens. Of interest to me were plantings that Piet Oudolf had designed in the city along the waterfront. One was found at Leuvehoofd, a park right on the Nieuwe Maas or New Meuse River.

Planting: A New Perspective by Piet Oudolf and Noel Kingsbury had just come out, and I snagged a copy before heading across the ocean, reading it furiously on the flight and during down time in the hotel. It was so interesting to have a guide to the planting right in my hands as I was visiting the site.

I approached the park from the south, where a long bed dominated by mixed grasses, Iris, and fading Allium came into view against a monument for those lost at sea in World War II. I would learn it was named De Boeg, which translates to The Bow in English. The memorial stands 150 feet tall with a pair of iron wings at the base that appear to be breaking water.

Iris sibirica ‘Perry’s Blue’ pops against the green foliage of grasses as the Allium above fade.

Turning a photo black and white so helps me appreciate the textures of the site. De Boeg was a war memorial to those lost at sea in World War II, and here it appears to be breaking through a colony of floating jellyfish

Here you can see how the naturalistic planting softens the starkness of the memorial.

From there four angular beds rippled out from the monument like waves getting larger until they hit the river’s edge. I quickly noticed that the planting this time of year had an overall cool color scheme of blues and purples. For a bit of brightness, down the center of the planting ran a river of Deschampsia cespitosa ‘Goldschleier’. Walking around the garden was interesting because viewing it from different points allowed me to see different perspectives and plant combinations.

Years ago, I downloaded several images from Piet Oudolf’s website to be able to study the designs. The one above is of an early rendition of Leuvehoofd that I cropped to show the four primary beds of the planting.

A perspective showing the essence of the planting at Luevehoofd Park. It is mostly a sea of green dotted with blue Amsonia, purple Allium, and the strip of Deschampsia.

One of my favorite photos from this experience was this view of the planting right next to the water with the Erasmusbrug or Erasmus bridge in the distance.

From this angle you can better see the mass of Deschampsia cespitosa ‘Goldschleier’ that runs through the center of the planting. You may notice on the drawing above that Sporobolus was recommended, but in the book Planting: A New Perspective, Deschampsia was mentioned instead. It was a nice glimpse at the iterative nature of developing a planting.

An unknown light blue Iris softens the sea of green. The design had called for Iris siberica ‘Perry’s Blue’, but it seemed that a few different blue variants were mixed in to play off the analogous color scheme.

A long view of the largest bed along the river front. The scattering of the Allium is quite apparent here. From this view I also really began to appreciate the presence of the matrix or groundcover level out of which other perennials arise.

Calamintha served as a skirt around Amsonia.

I also admired Piet’s ability to create combinations between plants to elevate the planting. This topic was one that Thomas Rainer and I discussed on the recent podcast, these small decisions about color, texture, and/or plant form made when pairing plants that really show the artist’s touch.

Here the colors of rosy purple Salvia nemorosa ‘Amethyst’ echo the umbels of Allium christophii.

Spires of Salvia nemorosa ‘Amethyst’ rise from a block within the planting.

Another example of color echo was between Allium christophii and Sedum ‘Matrona’. Both have hints of that smoky purple hue.

I also admired the repetition of starry shapes in parts of the planting. For example, here the stellate flowers of Amsonia are similar to the stellate flowers of the Allium. Perhaps they seem minuscule, but I believe such small choices are instrumental in elevating a design.

One final shot showing the blending line between the mass of Deschampsia cespitosa ‘Goldschleier’ and the mixed planting.

Overall, it was a good first introduction to a Piet Oudolf design. Leuvehoofd was moderately sized yet digestable. In the coming weeks, I’ll post a second planting I saw right down the river at Westerkade along with the lessons I learned there.

True Grit: Planting a Gravel Garden with Students

“How did I get here?” I asked myself in anxious jubilation last Friday as I watched the dump truck release its load of 6 cubic yards of gravel behind the agriculture building. The driver, a super nice guy named Mike, wished us luck on planting our gravel garden as he drove off. He had never heard of growing plants in gravel. And, up until a few years ago, really neither had I.

But, the rhetorical question really made me reflect. Why was I having students plant common perennials in gravel?

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Every two years I teach Herbaceous Plants, a class devoted to the annuals and perennials that will do well in east Texas and the southeast. This semester is the fourth time that I have taught the class, and each year I get a little more focused on the use of these plants in naturalistic design. In the past years, I’ve had students design and plant prototype designed plant communities in our edible garden. We deemed these food prairies since the garden was centered on food for people, and these plantings would provide food for insects. They would also provide food for the mind where the students and I could learn better how to do this sustainable type of planting.

Through the installation of naturalistic plantings, I’ve realized that the weed management is a constant struggle. While weeds are already a challenge during the active growing season, they are also problematic during the cooler months here in the southeast when the weather is mild enough to allow persnickety winter weeds to continue growing. The hope with naturalistic plantings is that they can close quickly enough to choke out potential weeds, and if the weed bank is depleted prior, it certainly helps. But, management often requires the use of mulch, pre-emergent herbicides, and/or wedding to control such issues. Other friends and colleagues have commented on their frustration that weed management after installation can be quite cumbersome especially with the dense planting used.

A Permanent Mulch

In my studies of naturalistic design, I’ve learned that weed management can be induced by increasing the stress of the site conditions and by lowering the level of nitrogen in the soil. An inorganic mulch layer of gravel, sand, recycled concrete, or other crushed aggregates achieves both of these goals. I first became aware of the science behind this approach when I heard Cassian Schmidt speak at the 2016 Perennial Plant Conference. He had detailed data down to minutes per square meter on how much management must occur for different types of plantings, and rocky soils that create more stressful conditions for the plants reduce management time. I realized I had seen these types of plantings before. I had visited Beth Chatto’s gravel garden in England where famously none of the plants have been irrigated. And, of course the gravel garden at Chanticleer has always captured my attention.

The gravel garden at Beth Chatto’s nursery in the UK was once a parking lot. It now features denizens from around the world that survive in more stressful conditions.

The gravel garden at Chanticleer hosts a wide range of species that tolerate growing in harsher conditions.

Hearing Cassian Schmidt’s presentation really piqued my interest in using gravel as a planting medium, but I had my doubts. I really hadn’t embraced that stress was an asset yet as I had studied about emulating nature in the other direction and enriching soils with organic matter to prevent problems with edibles. I started to think about the plant communities I had seen in west Texas or the North Carolina barrens. Perhaps it was possible, and we could make garden soil more stressful for plants.

I started looking for more information on the subject. I learned about Peter Korn and how he grows plants in straight sand conditions, and again, I was amazed that plants could survive in such a scenario. In 2019, I attended the Perennial Plant Association’s (PPA) meeting in Chicago, and on a tour visited Olbrich Botanical Gardens where Jeff Epping is director of horticulture. Right off the bus was an incredible perennial planting at the entrance. I would discover from the conversations of the people around me that the thriving plants I saw were planted in 4 to 5 inches of gravel! Once inside, we would discover other gravel plantings where Jeff had overseen their install. I’ll add here that I’ve learned much from looking at a presentation he gave at PPA in 2017.

Perennials thrive in a gravel garden at the entrance to Olbrich Botanical Gardens.

Here’s another gravel garden further in Olbrich Botanic Gardens that features Calamintha, Sporobolus, Allium, and other species.

Around the same time, I was delighted to see Ben O’Brien have success with planting in combinations of sand, gravel, and recycled concrete in Canada. He did some incredible trials of different species in these mixed aggregates, and the complete results of his work including a species-by-species breakdown of his trial can be found on his website.

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HOW WELL DO GRAVEL GARDENS WORK IN THE SOUTH?

But, most of these plantings are found up north—Wisconsin, Pennsylvania, Ontario, England, Germany, and Sweden. The question is will they work in the deep south where we get quite hot later in the summer and can have prolonged dry periods. And, again I’m not focusing on xeric or alpine plants but instead common perennials to grow in gravel.

So, I decided with my class this year that we would install a gravel garden to attempt to answer this question. This class would be slightly different because due to COVID-19 we condensed the class from16 weeks down to a half semester of 8 weeks. We would just double the time we met each week to cover the same material. But, that also meant we had to expedite the process of developing the garden.

I should also note for those of you concerned about my students or me in a COVID-19 environment that I have been extremely cautious. (I’m that cautious person who hasn’t eaten out in a restaurant since March 2020, hasn’t travelled to see family or really anywhere, and was told back last spring when I was rearranging my classes that I “drank the Kool-Aid” about the hyped-up concerns over COVID-19.) There were only seven students in the class, which allowed for social distancing through this entire course, and students wore masks as well, too.

Here is the site of our future gravel garden at the bottom of Sprout, our edible garden in the Plantery. The Plantery is our teaching gardens, grow houses, and micro-farm Sprout located near the SFA Agriculture building where we can provide students with hands-on learning opportunities.

Prior to installing the garden, I covered many of the basics of naturalistic design from competitor—stress-tolerator—ruderal survival strategies to Nigel Dunnett’s FLOW design method in class. Students easily understood Nigel’s classifications of anchors (primary plants in the installation), satellites (plants that provide seasonality around the anchors), matrix species (the groundcover species, typically grasses), and free floaters (self sowers that pop up here and there). We then practiced iterating and creating naturalistic plantings, first as students in small groups and then as solo projects.

For our gravel garden, I provided students with a plant list of species that we had both ordered and propagated. Normally, we would choose the plants early in class and then order them or grow them, but the shortened semester forced my hand. I also provided students with a rendering of the site dimensions where the students were able to apply what they learned in class, and from a measuring lab we determined that the full sun site was approximately 400 square feet in size. Below are two anonymous examples of the drawings that students developed for the class.

From these drawings I then synthesized them into one cohesive design. Again, normally, we would do this activity in class, but with the time limitations I decided to render the design myself. The design we went with was to have taller edge species at the back of the planting near the fence that my nursery management lab had built the previous fall. Then, a sinuous curve would snake through the bed with plant anchors and plant satellites arranged on either side of the bed. Some large rocks remained in the bed from a previous planting that students like to sit on and take pictures, and we decided to just use them as part of the design. The taller species would provide a nice floral backdrop and the pathway would pass right by these larger stones.

The biggest challenge was sourcing the mineral mulch. I had almost given up when I found a company in town that sold baked clay that is used on roads, and it appeared to be clean of weeds, had the angular size of grit that we desired, and had that gray-blue color that I had seen before at other gardens. It was a bit pricey coming in a $110 a cubic yard, but I was prepared to pay for good quality material. This gravel was delivered last Friday in anticipation of planting this week.

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TUESDAY MORNING CLASS, SPREADING THE GRAVEL

We finished leveling the soil in our morning class. We then put stakes in that had two markings, one for the soil line and one for the gravel line. Students then began to spread at least 4 inches of gravel over the entire site. We then went back and checked with trowels to make sure that the gravel depth was right over the bed.

A view of the site from the ground prior to any gravel. Oh, and in case you’re curious about the white in the Sprout garden, those are floating row covers over tomatoes. We had a freeze forecasted this week!

Students begin spreading gravel over the site.

The stakes really helped us check the gravel depth.

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TUESDAY AFTERNOON LAB, PLANTING THE ANCHORS AND SATELLITES

In the afternoon lab, we flagged our pathway and then began placing the the anchors and satellite species into the bed. I paired students off to look at the design and then place plants appropriately with notes on how many plants should be placed in each area. From reading about gravel gardens I was aware that we needed to knock off excess soil to decrease the organic matter in the bed and remove the top of the substrate from the rootballs to reduce the weed load we might be putting in the beds. So, when we began planting, I instructed students to use Tubtrugs to accomplish these tasks and not get soil in the gravel. Afterwards, we watered the plants in well.

Students begin setting out plants based on the design.

Mike and Hanna check the design for the placement of Symphyotrichum oblongifolium ‘Raydon’s Favorite’.

The anchors and satellites laid out prior to planting.

Brendan plants a Pycnanthemum tenuifolium into gravel.

Nyree knocks the soil off a Pycnanthemum tenuifolium plant.

Hope waters the plants in after planting.

The anchors and satellites planted into gravel.

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THURSDAY MORNING CLASS, PLANTING THE MATRIX

We wrapped up the planting Thursday morning by planting the matrix species. We planted more Nassella, and then we introduced a few Sporobolus heterolepis in the front and Muhlenbergia reverchonii in the back. We also scattered Echinacea purpurea and Echinacea purpurea ‘White Swan’ through the latter last two grasses to see how they will do on site as self sowers.

Planting round two begins with installing the matrix layer.

The gravel garden fully planted!!! Yay!!! We still haven’t decided what edging to use to mark the path. We may wait until the plants fill in a bit to determine that. We are thinking willow, bent metal, or maybe just leaving it bare.

An overview perspective of our new gravel garden. And, in case you are wondering about the area to the right of the gravel garden that’s been recently cleared, we eventually want to turn that into a practice patio garden where students can overhaul it every few years. Since we are a small program with limited funds, we tend to piecemeal projects together. This gravel garden pathway will feed right into the space as if it is part of an extended back yard to the mock patio.

As Jeff Epping suggested in his presentation, we will irrigate often for the next several weeks until plants are established. And, reflecting back over the whole process the one change I want to make is to try to find cheaper gravel that achieves the same effect as this baked clay product.

I look forward to seeing the true grit that these plantings will offer for us here in the southeast. I asked students what they loved most about this project. Common comments were how good it looked at the end, learning that plants could grow in gravel, and the excitement to see how the planting will look in a few months. I, too, have that same excitement, though with a dash of the fear of failure. But, I know that failure feeling is essential when trying something new that pushes the boundaries of what is possible and learning new things about horticulture. And, as I kidded with the students, should this fail, well, we have 6 cubic yards of gravel for our future walkways! :-)

Muhly by Morning, Muhly by Day

Autumn is a time of swift change in the garden as plants scurry to have their last hoorah before frost, and it is beautiful watching them play with varying environmental factors.  While much of these shifts occur over days or weeks, sometimes only a few hours can make the difference. 

A few years ago I witnessed such change at Chanticleer with Muhlenbergia capillaris on a crisp autumn morning in October. I was back again in the Philadelphia area speaking to a crowd of 600 at the Perennial Plant Conference. Seeing the garden again was a nice comparison because I had just been there that summer for my guest gardening experience (Day 1, Day 2, and Day 3). I was most excited to see the elevated walkway and how it had developed through the season. This part of the garden was where I headed first.

The elevated walkway has a westward facing slope where even if the sun has been up for an hour or two, parts of it can still be shrouded in shadow.  When I approached the overlook, the muhly left me breathless. 

Wow.

The panicles having soaked up the dew from the night now refracted light leaving little pink to be seen.  It was like a fog and reminded me of the milky clouds in the valleys that I've seen so many times driving the Blue Ridge Parkway further south.  And, having other plants like Eryngium yuccifolium and Kniphofia ‘Wet Dream’ emerging through the haze of plumes like otherworldly skyscrapers piercing stratus was a brilliant juxtaposition of plant heights and textures. 

This photograph I took that morning is one of my favorites of all time. It is three main characters with a few supporting cast, and it shows how such simple textures can create a spectacular view in a garden.

I've admired Muhlenbergia capillaris for many years, but this planting was the icing on the cake. I have no memory of seeing muhly grass when I was there earlier that summer. It is no surprise, though. Most of the growing season the plant is lost in the haze of chlorophyll.  But, when it comes into flower, its mist of cotton candy pink becomes a beacon in the landscape and leads every eye towards it. It goes from nobody to a celebrity overnight, and now, everyone wants it.

But, just like fog, the effect burned off later in the day.  I returned close to lunch to find the whole look had changed, and now I saw a totally different planting.  The rose-colored muhly I've known for so long was back after the dew vanished.  The sun was harsher now, and the towering plants blended into the landscape.  

Such experiences remind me that we need to visit our gardens at all times of day during this darkening season. We never know what nature hath wrought for us nor how long these special moments will last.

The same shot but only a few hours later.

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Many of you emailed from my previous posts on Chanticleer about how you enjoyed the photos. Here are some more images from that trip for your viewing pleasure. 

The teacup garden in its autumn exuberance.

Dew glistens on the ovate leaves of Euphorbia cotinifolia

Such a great cool color theme woven with Symphyotrichum, Plectranthus, Stachys, and Nicotiana.

Another part of the garden was warmed by the rising sun basking on red foliage and flowers. What a wonderful effect to echo the colors of summer Ensete in the fall foliage of an Acer palmatum.

The flowery lawn was at its height of color for the year.

Light shimmers through the emergent Verbena bonariensis in the flowery lawn.

Muhly grass acts a foil for Kniphofia ‘Wet Dream’…

…and as a web for the occasional Ascelpias seed.

Echinacea seedheads punctuate the gravel garden.

Liatris elegans erupts out of the gravel garden at Chanticleer.

Another view of muhly, this time on the rock ledge down from the gravel garden. Joe Henderson said he used more here to connect this planting with the elevated walkway and make the garden feel more cohesive.

Even in their fade, the Colchicum in the bulb meadow look good.

Another shot of the fallen Colchicum.

The Sporobolus meadow in its fall color

The old iteration of the cut flower garden looked spectacular during my visit.

Aster tataricus glows against the autumn sun.

Cajun Prairie

“I think there’s a prairie in Eunice,” Dawn Stover said as we drove past a sign indicating the Louisiana town a few miles ahead.

I replied, “Oh, really,” as I pulled out my phone to access Google maps to investigate.  Sure enough, just north of town I found a large swath of green with the label Cajun Prairie.

It was last fall, October 2019. We were on our way back to Nacogdoches from the International Plant Propagators’ Society-Southern Region meeting in Louisiana, Dawn and I upfront and Dawn’s greenhouse technician Jordan Cunningham was in the back.  “I’m fine to stop if y’all are,” I said.  Both agreed, and I plotted a course.  

At first, we unknowingly drove past the main ten-acre prairie.  GPS took us to a random spot in the road, and we kept driving to scope out the site.  North of the prairie, we found a gravel parking lot at a granary that we parked in off to the side.  We hopped out and immediately started fending off giant mosquitoes.  Well, I worse than Dawn and Jordan because I was sporting shorts.  So, I shimmied some jeans on over the shorts and the bloodsucking ceased.  But, such a trivial annoyance was worth it to see the field of yellow Helianthus and Solidago swaying in the breeze.  

An 18-wheeler that needed to pull in where we were forced us back in the car, and we drove back to the south side of the prairie and found the parking lot for the main entrance.  Here, we could see a narrow concrete path led off in both directions to allow visitors solid ground to enjoy the ecology.  It ended up being a rectangle walk around the whole area so that visitors could fully appreciate the site.

Saccharum flower heads bend in the breeze

A spot to sit and enjoy the cajun prairie.

The prairie was magical and wild on that cool, autumn day.  The colors were spectacular for fall with flowers and foliage across the field glowing under the drab sky. 

An incredible mix of forbs in the cajun prairie

What a view those houses have in the distance.

Kneeling down, you immerse yourself in the prairie and see a different perspective.

I saw many flora friends like Pycnanthemum tenufolium, Helianthus angustifolius, Arnoglossum ovatum, and Liatris pycnostachya.  I delighted in the color echos between the plant life and the urban sprawl.  There was the russet Schizachryium and the rusted granary roof, the white outbuildings and the ivory petals on Hibiscus moscheutos.  

What a color echo between the grass and the roof.

The petals on Hibiscus moscheutos shines bright white against the prairie.

A late Arnoglossum ovatum stands above the prairie

I always love getting in close and seeing the intricate detail of Arnoglossum flowers.

One species that composed the prairie tapestry that deserves wider use was Hyptis alata (clustered bushmint).  The plant reminds me of Eryngium yuccifolium with the orb inflorescences, but unlike rattlesnake master that clusters the flowers at the top, here the spheres are scattered up and down the stem and look like lollypops with their peduncles.  While I have a few plants at home, seeing them in habitat gave me ideas about how to intermingle them with wispy grasses.  

Hyptis alata tended to be grouped together in the prairie, likely because it sows itself nearby.

Another photograph of Hyptis paired with Schizachyrium, Helianthus, Solidago, and more.

I was also delighted to see the glaucous blades of Carex flaccosperma (or glaucodea, I can’t tell them apart this time of year) growing in the understory of this prairie jungle.  I have long suspected that these twelve-inch tall Carex species that thrive in varying light levels in my yard could grow underneath forbs as a matrix layer, and here it was doing just that in a cajun prairie in central Louisiana.  

Carex flaccosperma (or glaucodea) hiding on the ground plain under the taller perennials.

One new plant that I learned and suspect could be very useful in southern naturalistic plantings was Chromolaena ivifolia, ivyleaf thoroughwort.  Resembling a Conoclinium coelestinum (blue mistflower) on steroids, it tops out around 3–4 ft tall. We had seen it just days earlier near a bridge on our way to Baton Rouge, and here it was again.  The flowers were a rich sky blue, and in their fade they turn dark brown and appear as floating freckles on the golden face of the prairie.  

Such a beautiful blue flower on Chromolaena ivifolia that also contrasted well with the yellows from Helianthus and Solidago.

Even the spent flowers of Chromolaena ivifolia were ornamental when they turned dark brown.

It was interesting to note that no growth was over our heads.  Near the base of some plants I noticed what appeared regrowth from a cut as well as tractor treads that should have been long gone.  I wondered if this prairie had been mowed sometime earlier in summer, and I’d love to talk with those who maintain it to learn if that’s correct. Another observation supporting my hypothesis was how late the Hyptis and Liatris were blooming.  Both were already setting seed at my house back in Texas, yet here they were in full bloom.    

Having soaked in as much of the cajun prairie as we could, we headed back to the car to return home.  I thought cajun prairie was just a label, but after reading more about these ecosystems I’ve learned they are unique and different.  

What we saw today was a recreated remnant, planted back in 1988 by volunteers and those that wanted to share what much of the southeast used to resemble before we humans came along.   I admire the efforts of all those who helped to create this prairie as a lasting vision. Visiting it was great mental fodder as I continue my search for flora to use in naturalistic plantings in the southeast US.  

One last look at the cajun prairie in Eunice, Louisiana.

Say Hi to Hymenopappus artemisiifolius

Spring is a ripe time to enjoy self sowers and volunteers like Papaver, Nigella, Centaurea, Consolida, and more.   I believe Hymenopappus artimissifolius belongs in with that bunch.  It’s a mouthful to say for such a lovely ruderal.  Old plainsman is the common name—so wise sounding for such a short lived plant.  

After we bought our house, I noticed this tall white flower on the roadsides near our house and wondered what delightful plant it was.  From a distance in bud it looks a bit like ping pong balls on a gray-green stick.  But, upon closer inspection you find a flower that resembles Astrantia.  There’s even hints of pink in it.  They are from two different families as Astrantia is Apiaceae, and Hymenopappus is Asteraceae.

I’m happy I live an an area where it occurs. This native’s range is limited to three states—Texas, Louisiana, and the southwest corner of Arksansas. But, it deserves wider use. Since it’s a biennial, my only concern is the hardiness of the basal rosettes. I have seen some germinate in late winter. Perhaps this late planting is an option for those who wish to try it further north.

Such lovely Astrantia like flowers. Note the white phyllaries, or modified showy bracts.

Unlike most of the self sowers, the color on old plainsman comes from modified bracts (also called phyllaries) instead of petals or ray florets.  Therefore, the essence of the plant appearing in flower lasts for much longer.  And, its height is much desired early in the season. I believe that both these contenders make the case that it is a great candidate for being a scatter plant in a naturalistic planting.

I haven’t quite figured out the germination requirements for this plant yet.  I scattered what little seed I had last year, and it seems I’ve had better success getting it to grow in our turf than the beds where I want it to reside.  But, once I do, you can be sure that I’ll have tons of it growing in my garden.  

Here’s a photo of the basal rosette of Hymenopappus artemisiifolius. One can barely see the discolor between the green tops and the silvery leaf bottoms.

My Planting for a Monarch

I’m getting antsy.  Spring is on its way.  The weather lately has been in the 60’s and 70’s, Narcissus and Muscari are in bloom, and dormant perennials are popping out of the ground.  Sure, we’ll have a few more frosts (maybe a freeze?), but being just a few weeks away from the first official day of spring, this gardening season is about to get goin’ and growin’.

One goal I have this year is to finalize the design of a few beds near our garage.  They’ve been mostly a holding cell for potted plants that right after we bought the house I plopped into the ground to save from incessant August watering.  

In my mental iterations of design, I’m not only considering beauty, harmony, and seasonality for these plantings but also management, survival strategies, and the benefits to insects and wildlife.  The critters seem to get the short end of the straw when planting versus the elements of design, but that seems to be changing with the increase of the public’s awareness of ecology and our role to make the world a better (or, if we don’t act a worse...) place.  

Many people believe that to have a garden good for wildlife your yard has to more closely resemble an unmown field, but what if I told you research shows that making a few small changes to the way you plant could help increase an insect’s survival and even perhaps their numbers?  

That’s what the recent paper “Configuration and Location of Small Urban Gardens Affect Colonization by Monarch Butterflies” by Adam Baker and Daniel Potter in Frontiers in Ecology and Evolution indicates.  It’s a technical title, but the basic hypothesis they tested was does the way we plant Asclepias (milkweed) species impact how Monarchs can find the plants and subsequently lay eggs on them?  

And, yippie! The whole paper is available online for people to read. I really enjoyed diving into this paper.  The research was broken down into three parts—investigating Monarch waystation gardens, synthesizing planting configurations, and looking at surrounding vegetation.  And, I have used their figures only to help you understand their work. All credit for the following figures goes to these researchers.

MONARCH WAYSTATIONS

For the Monarch waystation gardens, they visited 22 gardens that contained three species of Asclepias (A. incarnata, A. syriaca, and A. tuberosa).  They asked two great questions about each garden—were the plants blocked or mixed, and can Monarchs see the plants on a north-south approach.  

The former question is interesting from a naturalistic planting perspective because blocking versus mixing are two different approaches for laying out plants.  Oudolf and Kingsbury go in greater detail about both approaches in their book Planting: A New Perspective.  In my mind, if you had asked me before this study which would be better for insect populations, I would have said mixed.  A diverse habitat has been shown to support more species (more on this theory in a minute).  But, the research showed that these blocked or as they called them structured plantings had more Monarchs and eggs on them than the mixed plantings.  

In these waystations, they also evaluated whether plants could be accessed along a north-south gradient. Monarchs fly north from overwintering in Mexico, and then they fly south at the end of the growing season.  And, while the paper does say that they can fly any direction in a garden, planting Asclepias so they are visible in this north-south migration path seems to increase the number of Monarchs encountered and eggs laid on plants.  

This figure from from Baker and Potter’s (2019) paper shows that gardens that had structured (aka blocked) Ascelpias had more Monarchs than non-structured (aka mixed) plantings! Additionally, gardens that featured Asclepias that could be viewed on a north-south trajectory had more Monarchs as well. Note: ramet is a fancy word used to describe the number of shoots from a clonal colony. So, if an Asclepias plant has 10 shoots, those are 10 ramets.

PLANTING CONFIGURATIONS

A second step they took in their research was to create three different planting modules for evaluating Monarch counts—Asclepias on the perimeter, Asclepias in the middle, and Asclepias in a mixed planting.  All three gardens contained the same number of plants and fillers like nectar-rich Tithonia rotundifolia and Zinnia elegans and the tall ornamental grass Calamagrostis × acutiflora. 

Here’s a figure I pulled from Baker and Potter’s (2019) work that helps to illustrate their planting configurations.

Again, if you asked me before reading this, I would have guessed that the mixed planting would be the best.  But, their two years of data collection showed that the perimeter plantings had roughly DOUBLE TO QUADRUPLE the number of eggs and larvae as the other two plantings.  Wow.  I was blown away.  They cite a whole plethora of reasons and that having non-host plants (like the Zinnia, Calamagrostis, and Tithonia) might interfere with egg laying by Monarchs onto the host-plant Asclepias—blocking, shading, mixing volatiles, and landing on the wrong plant too many times. And, it appears that if enough of these compound together, the number of eggs and larvae on plants are drastically reduced.

And, here’s Baker and Potter’s (2019) data of Monarch eggs and larvae counts from those planting configurations. Absolutely amazing. Asclepias that were on the perimeter had double to quadruple the number of Monarch youngsters.

I mentioned earlier that increasing diversity (like we see in mixed plantings) can potentially help to support more insects.  What if the mixed configuration had more predatory insects?  They thought of that by trapping predatory insects and noted they didn’t really see a difference between the perimeter and mixed configurations.  Thus, there weren’t insects reducing the numbers of Monarchs in the mixed configuration relative to the perimeter planting.  

Basically, they created an unimpeded monoculture for the Monarchs.  We talk about how monocultures are bad because a group of plants en masse can have more pests than being mixed in a polyculture, but this research flipped that thinking on its head.  That if you want to plant something for a desirable “pest”, then block it and put it where they can see it.  

They do make a note in the discussion about the perimeter plantings. Because the between plant distances were greater in the perimeter planting and because Monarchs do prefer to lay eggs on isolated plants, this effect may have had an influence.

ASCLEPIAS HIDE AND SEEK

The last experiment they did was to investigate effects of surrounding vegetation over two weeks.  They planted Asclepias incarnata by itself and then hidden by Panicum virgatum ‘Shenandoah’.  The two plants didn’t touch (mind your bubble, switchgrass!), but the Pancium were close enough to hide the plants.  They observed that unimpeded Asclepias plants had on average a little over three eggs per plant while those screened by the Panicum had nearly zero eggs.  

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So, the things I took away from this paper about planting for Monarchs:

• Plant Asclepias in blocks with adequate spacing between plants.

• Plant Asclepias so that Monarchs have north-south access to the plants.  

• Plant Asclepias on the edges of your garden.

• Plant Asclepias so that surrounding vegetation doesn’t hinder access to the plants.  

And, that’s how I’m going to do it.  I have some locally sourced Asclepias seed, and once I get the plants going, I’m going to plant them in a couple of blocks on the outside of my beds with a few mixed in here and there for harmony.  

Now, the question is does this approach also work for other insects?  Of course, it would take more research to answer that question.  Some insects don’t migrate; therefore, the north-south access might be less important for them.  But, I do think that locating host-plant species near the edge, in blocks, and making sure they are accessible could be extrapolated to planting for other species of insects.  

A final note.  I don’t usually set down and digest a scientific article like this, but I was so impressed by the research and the content that I had to share it.  If you like this reflection writing, let me know, and I’ll consider doing more in the future.   

Pin the Plant on the Triangle

This semester, one of the classes I’m teaching is herbaceous plants, and I’m taking the class beyond the usual discussions of annuals and perennials.  From studying herbaceous plant communities, one of the most useful concepts that I’ve learned in recent years is the classification of a plant’s survival strategies.  

I’ve written about it before here and here.  As a refresher, Grime pitched that plants had three strategies based on environmental factors.  

• COMPETITORS are plants that take advantages of any and all resources they can muster.  They grow tall and wide to take out the competition.  Usually these stalwarts are perennial in nature, and they grow where stress and disturbance are nil.

• STRESS-TOLERATORS are plants that have adaptations to ensure survival when stress arises and conditions deteriorate.  They are usually perennial and can take many years to flower from seed.

• RUDERALS are short-lived annuals or biennials that are frequently exposed to some type of disturbance, which has selected for plants that quickly produce seed.

Usually, this strategy is visualized using a triangle (much like the soil texture triangle!) where a certain species can be shown to be—pulling some numbers out of the air—say, 70% competitor, 20% ruderal, and 10% stress tolerator based on the characteristics they exhibit.  

A figure of Grime’s triangle from Pierre et al. (2017) titled A global method for calculating plant CSR ecological strategies applied across biomes world-wide. As you can see the authors attempted to classify plants across the globe based on their tendency to be a competitor, stress-tolerator, or ruderal.

How do you take this concept from theory to application for students? Much research and data collection is needed to be able to precisely place a plant on the triangle.  Can it be done in a more simple fashion?  

After we covered the CSR theory in class, I did an activity with students.  I gave small groups (three to four) a list of seven different herbaceous plants and asked them to look up information and pictures online and try to determine where on Grime’s triangle it would fit.  I drew a triangle on the board labeling the sides and gave them markers and half sheets of paper for writing plant names.  

I then challenged them in pin-the-tail-on-the-donkey fashion (no blindfolds or sharp objects though!) to figure out where on the triangle the species would go by searching for it online.  Students looked for tendencies to spread, cover large areas, form large clumps, and/or have rhizomes (COMPETITOR); tendencies to produce copious amounts of seed, occur in areas of disturbance, and/or be short lived (RUDERAL); and tendencies to live in a stressful habitat, take a long time to flower, and/or have storage organs (STRESS-TOLERATOR).

One by one they started coming up and making educated guesses.  I stood by the triangle to offer advice and suggestions.  Some hit the nail on the head while others needed a little bit of coaxing to the right place.  

At the end, we went over the 20 or so species I provided as a challenge.  Again, I explained that while some species neatly fit into one group, some straddle the fence like Liatris elegans.  It has a corm (a stem-derived storage organ indicating some level of stress toleration) yet produces copious amounts of seed (traits of a ruderal).  

Pin the plant on the triangle—a fun game to teach students about plant survival strategies. Based on your plant knowledge, how do you think they did?

As gardeners it’s very helpful to think about flora in this way.  It helps us anticipate how plants will perform.  It explains why Gaillardia and Aquilegia don’t live long as perennials (ruderals), why Mentha and Monarda spread like crazy (competitors), and why Trillium and Narcissus  take 3–7 years to flower from seed (stress-tolerators).   It also allows us to envision how to combine plants.  Maybe put that runaway competitor in a drier spot to keep it from taking over creation?  Or, sow some ruderals in between the stress-tolerators to keep weeds down.  

If students can decide approximately which section of the triangle plants fit in during a 15 minute activity using search engines, then we can by watching how plants grow over the course of a year. 

So, that’s your homework for the season. Draw a triangle and see if you can’t plot where the species in your garden fit.