The juglone challenge

Sometimes, a project takes on an element of gambling. Recently, a couple asked me to help them spruce up their parking strip. It had nice, generous dimensions (12′ x 50′), but also came with a large Black Walnut tree. Being that they were new to Oregon, and not really familiar with what grows here, I invited them to walk around the nursery with me, and point out the stuff they liked. It was fun! They both turned out to have discerning tastes, which made the project so much more exciting. They also requested mixing up any exotics with native and drought tolerant plants. After I had a better idea of their aesthetics and wishes, and we had assembled a group of plants that would work in the given light conditions, I now had to figure out if the plants they liked would actually survive under that Walnut tree.  Walnuts emit juglone – a chemical comound –  into the surrounding soil, in a process referred to as allelopathy. Allelopathy is essentially a plant’s way to bully surrounding plants into submission and hamper their growth – thus reducing their competition, and establishing its own dominance. It’s pretty fascinating stuff – you can read more about it here.

This is where we started. Two unused raised beds in the sunny end....

This is where we started. Two unused raised beds in the sunny end….

... and nothing but brown grass in the shade under the tree.

… and nothing but brown grass in the shade under the tree.

There are ample lists of Do’s or Don’ts available on the Internet, but several of the plants we had weren’t expressed on any of the lists. So, on some, we had to just take a chance, and do our own experimenting. Long story short, some of their choices were deemed fine, and some were exchanged for other safer bets. And, on some, we just gambled. As a general rule, a plant intolerant of juglone will die within the first few days.  Happily, by now, the plants have been in the ground for over a month, and everything is doing great!

As you could see in the photos – due to the expansive reach of the Walnut tree, the strip is mostly shady, except on one end where it is baking hot and sunny. To begin with, we added a couple of flagstone and river rock pathways to the curbside – both for ease if visitor’s parking, but also to be able to “be inside” the new plantings. In one place, the lowest Walnut branch curves elegantly upward before bending down again, thus offering a natural portal for one of the paths. We also added a few boulders. At the sunny end, we put three of them rather close together, and filled the space between them with soil, building up a kind of “planter” for our feature plant; a little dwarf Chinese Elm (Ulmus parvifolia ‘Seiju’).

Boulders being delivered!

Boulders being delivered!

Here is the path going in under the arching branch.

Here is the path going in under the arching branch.

Both grasses and ferns are said to be mostly juglone tolerant, so those were easy choices. (Plus, those are such great texture plants anyway, so I think most every project would benefit from including some!) Anyway, for the benefit of anyone else attempting to plant around a Walnut tree – here are some plants that work; For larger focal points for partial sun and shade areas, we chose a few interesting evergreens –  Pernettya rubra with its adorable pink berries, a Daphne ‘Carol Mackie’ for some fragrance, and the amazingly beautiful Mahonia gracilipes, with the lovely white undersides of its leaves glowing in the dark. Overall, other than Sword ferns, the natives we used include Dicentra, Camassia, and Sysirinchium (Blue-eyed grass). We also planted a ground cover rose ‘Snow Carpet’, Reineckia, Epimedium, Pachysandra, Angelina sedum, Artemisia ‘Seafoam’, Iris pallida, and Agastache ‘Apache sunset’, and Zauschneria californica. The grasses included Deschampsia ‘Schottland, Miscanthus sinensis ‘Morning light’, Boutlea ‘Blonde Ambition’, Nasella tenuissima, native Luzula nivea, and Carex ‘Evergold’. It’s only been a month since planting, but everything is already filling in quite nicely. 🙂

Rocks and paths in place, and everything planted.

Rocks and paths in place, and everything planted. The larger shrub on the right in the foreground is the Pernettya.

Here is a different view toward the sunny end. Grasses, ground cover roses, and of course that cute little Elm.

Here is a different view toward the sunny end. Grasses, ground cover roses, and of course that cute little Elm.

Pernettya, Epimedium and Reineckia.

Pernettya, Epimedium and Reineckia.


The shady end has a different feel, with ferns, Luzula grass, Epimedium, and Pachysandra. We planted a Daphne ‘Carol Mackie’ for fragrance…

... and of course that wonderful Mahonia gracilipes. Just look at the marvelous white undersides of those leaves!

… and of course that wonderful Mahonia gracilipes. Just look at the marvelous white undersides of those leaves! I think that will be a great color echo to the white edges of Carol Mackie.


Looking back toward the sunny end from the street. Looks so much better than just brown grass – don’t you agree?

About annamadeit

Born and raised in Sweden, my aesthetics and outlook on life are strongly shaped by a culture rich in history and tradition. I care a great deal about environmental responsibility, and my aesthetic reflects the visually clean, functional practicality and sustainable solutions that are the hallmarks of modern Scandinavia. I was trained as an architect at the University of Cincinnati and as a color specialist at the Scandinavian Colour Institute in Stockholm. I'm obsessed with plants and gardens, and aim to take my skill set a step further by designing gardens as well as interiors. As someone so aptly said: " Architecture is the skin that separates the exterior from the interior". So true - you can't successfully focus on one without incorporating the other. I'm also an avid cook, and I love to ski. In addition, I put time and efforts into trying to rectify things that I feel are wrong in my immediate community. As you will see, The Creative Flux will touch on all these things, and more. For sure, it's all over the map, but then again - so am I! Welcome to my blog!
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14 Responses to The juglone challenge

  1. mattb325 says:

    Massive improvement – it’s the nicest hell-strip on the block. (In fact it should no longer be called a hell strip)

  2. Mark and Gaz says:

    Much better! And hopefully the juglone effect won’t have much effect 🙂

    • annamadeit says:

      Thanks. No – supposedly it only takes a couple of days before you can see any effect, so you’ll know quickly if you put the wrong plant in there. I think it’s safe to say we’re off the hook! 🙂

  3. Incredible job, Anna. You amaze me and I’m so lucky to be able to work with you. You have the ability to see the potential of a site and also to select a diverse variety of plants and know exactly where to place them. Fabulous!!

  4. rickii says:

    From Hell to Heaven in one fell swoop. This should be the start of something good, as neighbors see the beauty that could be theirs.

  5. rusty duck says:

    That looks brilliant. The client must be delighted.

  6. Kris P says:

    It looks great Anna! I’ve been struggling with one area of my garden that used to support a 60-foot Eucalyptus tree. Although the stump was ground down when the tree was removed 2 years ago, I’ve had problems growing anything in that area and have concluded that the rumors about the allelopathic qualities of Eucalyptus may not be rumor after all. I’m going to berm the soil in the area and try replanting (again) this fall. I’ll follow your example and try to find resistant plants.

    • annamadeit says:

      Thanks, Kris! Hmmm, I wonder if the toxins emitted from the Euca is the same as the ones from the Walnut…? Keep us posted on what you find, would you please? I’d be very interested to learn.

  7. I think it looks awesome! I love it! I really love all the stone. 🙂

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