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| A dense carpet of woodland perennials. Thomas Rainer, a landscape architect, calls plants “social creatures” that thrive in particular networks. Credit Mark Baldwin |
It turns out I’ve
been missing what the plants were trying to tell me, failing to read botanical
body language and behavior that could help me put plants together in
combinations that would solve challenges that many of us have: beds that aren’t
quite working visually, and garden areas that don’t function without lots of
maintenance.
As we gardeners
shop the catalogs or the just-opening local garden centers with an eye to
finally “fixing” that bed out front that has never quite cooperated, I asked
Mr. Rainer, a landscape architect based in Washington, D.C., to lend us his 3-D
vision.
In his career, Mr. Rainer has
designed landscapes for the United States Capitol grounds, the Martin Luther
King Jr. Memorial and the New York Botanical Garden, as well as gardens from
Maine to Florida. He is an author with Claudia West of the 2015 book “Planting
in a Post-Wild World: Designing Plant Communities for Resilient Landscapes.”
He is a principal in the firm Rhodeside & Harwell, but will leave soon to
start a new firm with his wife, the landscape architect Melissa Rainer, and Ms.
West. He advocates an ecologically expressive aesthetic that interprets rather
than imitates nature.
Q. You visit a
lot of gardens, and probably hear from gardeners like me with beds that just
aren’t working. What’s the most common cause?
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| Traditional garden design often isolates plants, setting them “as individual objects in a sea of mulch,” Mr. Rainer said. “We place them in solitary confinement.” Credit Thomas Rainer |
A. First, we have
to understand that plants are social creatures. Our garden plants evolved as
members of diverse social networks. Take a butterfly weed (Asclepias tuberosa,
named this year’s Perennial Plant of the Year by the industry
group the Perennial Plant Association), for example. The height of its flower
is exactly the height of the grasses it grows among. Its narrow leaves hug its
stems to efficiently emerge through a crowded mix. It has a taproot that drills
through the fibrous roots of grasses. Everything about that plant is a reaction
to its social network. And it is these social networks that make plantings so
resilient.
So if we think
about the way plants grow in the wild, it helps us understand how different our
gardens are. In the wild, every square inch of soil is covered with a mosaic of
interlocking plants, but in our gardens, we arrange plants as individual
objects in a sea of mulch. We place them in solitary confinement.
So if you want to
add butterfly weed to your garden, you might drift it in beds several feet
apart and tuck some low grasses in as companions, like prairie dropseed, blue
grama grass or buffalo grass.
Start by looking
for bare soil. It is everywhere in our gardens and landscapes. Even in beds
with shrubs in them, there are often large expanses of bare soil underneath.
It’s incredibly high-maintenance. It requires multiple applications of bark
mulch a year, pre-emergent herbicides and lots and lots of weeding.
The alternative
to mulch is green mulch — that is, plants. This includes a wide range of
herbaceous plants that cover soil, like clump-forming sedges, rhizomatous
strawberries or golden groundsel, and self-seeding columbine or woodland
poppies.
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| Intermingling plants can also foster more flowering plants in a smaller space. Credit Thomas Rainer |
Q. If I want
to try to do it more as nature does, what am I aiming for? Where do I take my
cues?
A. The big shift
in horticulture in the next decade will be a shift from thinking about plants
as individual objects to communities of interrelated species. We think it’s
possible to create designed plant communities: stylized versions of naturally
occurring ones, adapted to work in our gardens and landscapes. This is not
ecological restoration, it’s a hybrid of ecology and horticulture. We take
inspiration from the layered structure in the wild, but combine it with the
legibility and design of horticulture. It is the best of both worlds: the
functionality and biodiversity of an ecological approach, but also the focus on
beauty, order and color that horticulture has given us. It’s possible to
balance diversity with legibility, ecology with aesthetics.
And it is a shift
in how we take care of our gardens: a focus on management, not maintenance.
When you plant in communities, you manage the entire plantings, not each
individual plant. This is a pretty radical shift. It’s O.K. if a plant
self-seeds around a bit, or if one plant becomes more dominant. As long as it
fits the aesthetic and functional goals. We can do much less and get more.
Q. Sort of
gives new meaning to the phrase “community garden,” doesn’t it?
A. Yes. And
plants each also have particular behavior — whether it wants to hang out with
other plants of its own species or not. So many gardening mistakes are a result
of not paying attention to this.
Q. You make
them sound like social animals, which makes me think I’ve been shallow,
objectifying plants — choosing among them for just another pretty face, instead
of reading their body language to get at their true nature.
A. One of the
most useful ideas that came out of our research was this German idea
of sociability, developed by Richard Hansen and Friedrich Stahl. They rank
a plant’s predilection to spread on a scale of 1 to 5. A low-sociability plant
is one that in the wild is almost always found by itself (Panicum virgatum, for
example, is almost always found by itself in a meadow). A high-sociability
plant is one that spreads into large colonies (Epimedium or Tiarella cordifolia
are Level 4 plants; Carex pensylvanica and Packera aurea are Level 5). You
arrange plants according to their sociability level: Plants of lower levels (1
and 2) are set individually or in small clusters. Plants of higher levels (3 to
5) are set in groups of 10 to 20-plus, arranged loosely around the others.
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| A meadow-like display of greenery on an urban deck designed by the HM White landscaping firm. Credit Aaron Booher |
It sounds geeky,
ranking plants on a scale, but it’s useful because it informs which you should
mass, and which you should mingle. It’s why a mass of 50 echinacea (Level 2)
tends to flop. They’re just not meant to cover ground. But if you scatter a
handful of echinacea in a mass of prairie dropseed or sideoats grama, it will
look great.
For years, I
would pack together large grasses like switchgrass, or flowers like garden phlox
(both Level 1 plants) and wonder why they got rust or powdery mildew. But if
you find phlox in the wild, it will never have mildew. It’s growing out of a
lot of lower plants, so it gets good air circulation. This idea changed the way
I look at plants and pay attention to how they behave.
Q. I know that
nature doesn’t plop a 50-foot tree in a mowed lawn (or mow its lawn at all,
actually), so that’s not the winning design tactic. I also know that more
diverse layered designs are richer ecologically — and now you are saying they
are easier to manage, too. But how do I figure out how to fit the right plants
together?
A. We need to
start thinking about how, not what. So many garden books focus on what to
plant, but so few focus on how to arrange plants to fit together in ecological
combinations. When we fit our plants together like a tight jigsaw puzzle, the
maintenance goes way, way down. They start becoming resilient systems rather
than random objects.
To do this, we
need to pay attention to a plant’s shape. Its shape is often an indication of
where it grows in the vertical strata of a plant community. Upright plants with
low or minimal basal foliage like Joe Pye weed (Eutrochium) or spiky upright
plants like beargrass (Nolina bigelovii) have adapted to growing through other
plants. Horizontally spreading rhizomatous plants like Pennsylvania sedge
(Carex pensylvanica) or beach strawberry (Fragaria chiloensis) have adapted to
grow underneath others. You almost have to look at a plant from the vantage
point of a chipmunk to see its shape.
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| A grouping of plants by sociability: Foamflower (a very sociable Level 5) dominates, followed by wild ginger and trillium (Levels 2 to 3) and just a few ferns (more independent at Level 1). Credit John Roger Palmour |
What I love about
this layering idea is that it gives gardeners flexibility. Those lower layers
should be very biodiverse: lots of different plants covering the ground and
providing stability. But diversity in this layer does not really look messy,
because most of these plants are growing underneath our taller ones, so you
don’t really see them.
In my garden, I
have a corner with dry shade where I have a handful of shrubs that screens a
busy road. Lately I’ve been adding white wood aster (Eurybia divaricata),
Appalachian barren strawberry (Geum fragarioides) and Pennsylvania sedge and
watching them fill the gaps. Upper layers, on the other hand, are the ones I
consider the “design” layers because they shape your impression of the
planting. You can arrange them naturalistically, or in neat clumps — whatever
style you like. That’s the flexibility: The order and legibility of the upper
layers combines with the diversity and functionality of the lower ones.
The really cool
thing is you can combine this layering idea with the sociability idea. Those
Level 1 and 2 sociability plants tend to be those taller upright plants you use
in the top layers of your garden because they like to grow through others. The
Level 3 to 5 plants tend to be your lower spreading ground-hugging species.
Q. So I am not
shopping for plants solely as decorative objects, but for plants with a purpose
— for instance, as a living mulch or a good companion to others. Of course none
of that, neither the “sociability” nor the plant’s layer, is on the plant
labels. A tag might say “for containers or landscapes” or that the plant is
“trailing” or “upright” or “mounding,” but that’s about it. What should the
label say to help me put plants together successfully?
A. My dream label
would describe things that are actually useful to understanding how it grows.
It would describe its shape, its root system (taprooted, deep fibrous roots,
shallow horizontal roots); its life span (a short-lived pioneer like columbine,
or a long-lasting lavender); its sociability level; its adaptation to stress
(quick-establishing, but short-lived ruderal species like Gaura lindheimeri or
Nassella tenuissima; a thuggish, fast-spreading competitor like Monarda didyma;
or a slow but steady stress-tolerator like Hosta or Calamintha). These are
really the factors that explain how it will grow in our gardens.
Q. Where can
we learn more? Being Northeastern, I love studying plants on the Go Botany plant finder from the
New England Wildflower
Society, for instance.
A. The Mt. Cuba Center, the Lady Bird Johnson Wildflower Center
and the California Native Plant Society
websites all have excellent information about how a plant grows in the wild and
what it grows with. But mostly, I think gardeners can get to know their plants
by going outside and getting reacquainted. Take a look at their shape, how they
spread and see what they are trying to show you. You can learn a lot.
https://www.nytimes.com/2017/04/30/style/understanding-what-makes-plants-happy.html?nytmobile=0&_r=0
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