Walnut Guild 🌳
A large black walnut tree lives in the back yard.
I would like to find California native companion plants for it, but have had a difficult time.
Something about the soil makes me think it’s poor. It’s clay to begin with, but also full of gravel, construction debris and covered by barrier plastic and pea gravel, pavers and bricks in many places. Few things grow well.
The walnut and neighboring buildings cast the yard in shade. California is frequently in drought, so it’s dry. I’ve recently learned walnuts are allelopathic, releasing the toxin juglone. Fwiw, neither an arborist we consulted regarding the health of the walnut, nor the city arborist, expressed concern about juglone toxicity wrt other trees in the yard.
The Black Walnut Dispatch inspires me to take and share notes so we might all learn together.
The permaculture discipline has also been helpful, not least because it has many handy phrases like guild (recreations of plant communities found in nature) and companion plants (symbiotic or mutually supportive), and concepts like a seven-layer garden and soil building.
I’ve found Gaia’s Garden by Toby Hemenway a concise introduction to permaculture, and it even has an in-depth description of a walnut guild!
Paul Stamets, a hero, is a fan of permaculture and proposes a Stametsian Model with an eighth layer for fungi.
So, the challenge is: build a juglone-, drought- and shade-tolerant California native guild around the walnut.
Here are the plants I’ve tried:
|Latin name||Common name||Layer||Health*||Proximity*||Sun*||Water*||Notes|
|Achillea millefolium californica||California yarrow||Herb||3||1||4||1||Suspect more sun needed, but one in the front yard in shade is fuller. Juglone tolerant per 1|
|Allium triquetrum||Three-cornered leek||Herb||5||1||2-4||1||Self-propagating. Juglone tolerant per 1. Curious to try a native Allium like Allium unifolium|
|Agapanthus praecox orientalis||Lilly of the Nile||Shrub||2||1||3||1||This was doing well, but then started yellowing. Agapanthus is prolific in the front yard in shade, for comparison|
|Aquilegia eximia||Serpentine columbine||Shrub||1||1||2||2||The columbine’s health steadily declined after planting, dropping leaves and never flowering. Transplanted to pot with potting soil and more sun and care and it rebounded.|
|Artemisia douglasiana||California Mugwort||Herb||2||2||4||1||Died back completely in summer, but resprouted and grew vigorously after Spring rain|
|Asarum caudatum||Western wild ginger||Root||4||3||2||2||Leaves look good, but growth is slow and it hasn’t flowered. I suspect it needs more water|
|Brugmansia arborea||Trumpet flower||Low tree||4||2||4||1||Flowering and leaves look good. Suspect more sun needed|
|Callistemon rigidus||Bottlebrush tree||Low tree||5||3||4||1||Flowers profusely year-round|
|Citrus tangerina||Tangerine tree||Low tree||2||1||3||1||The tree produces inedible fruit and its leaves are chlorotic and sparse :( I suspect it gets insufficient sun. An arborist mentioned citrus trees are “hungry”, so this one may just need fertilizer. There’s a lemon tree in the front yard that looks great, for comparison|
|Camellia japonica||Camelia||Low tree||1 & 5||3||2-3||2||Two camellias on the property outside dripline. One in good health, but one suddenly whithered. Suspecting gophers although they left the other alone.|
|Claytonia sibirica||Candy flower||Herb||5||3||2||2||Leaves and growth look good|
|Satureja douglasii||Yerba buena||Ground||4||1||2||2||Leaves look good, but growth is slow. Spring rain didn’t improve. Suspect more sun needed|
|Dicentra formosa||Bleeding heart||Shrub||5||1||2||2||Planted two. Died back completely after summer, but resprouted and spread vigorously after Spring rain|
|Dietes iridioides||African iris||Shrub||5||1||3||1||Flowers and seeds readily. Juglone tolerant per 1|
|Festuca californica||California fescue||Ground||1||2||1||New planting🤞|
|Fragaria californica||Wild strawberry||Ground||3||1||3||1||Spreading and leaves look good, but not flowering. Suspect more sun needed|
|Hedera helix||English ivy||Vine||5||2||3||1||Well-established when I moved in. Grows vigorously on wall at dripline. Less vigorously inside dripline|
|Heracleum maximum||Cow parsnip||Shrub||4||1||2||2||Under dripline. Planted two. Both died back, but returned with Spring rain. Leaves good so far|
|Holodiscus discolor||Cream bush||Shrub||4||1||2||2||Leaves look good, but slow growing|
|Horkelia californica||California horkelia||Ground||4||1||3||1||Hasn’t flowered or spread. Suspect more sun needed. Doubled in size after Spring rain|
|Hydrangea macrophylla||Hydrangea||Shrub||1||3||3||1||A tall shrub growing in shade when I moved in. Declining health perhaps due to low water or sun|
|Iris douglasiana||Douglas Iris||Shrub||4||1||3||1||Planted two. One died. The other’s leaves look good, but it hasn’t flowered. There’s another iris nearby that’s flowering, for comparison. Juglone tolerant per 1|
|Ligustrum japonicum||Japanese Privet||Low tree||5||1||2||1||Predates me. Healthy/invasive.|
|Lupinus arboreus||Yellow bush lupine||Shrub||1||4||1||New planting in a relatively sunny spot🤞 I read somewhere nitrogen fixers are generally juglone-tolerant|
|Lupinus variicolor||Varied lupine||Shrub||1||4||1||Demolished by slugs and squirrels|
|Mimulus aurantiacus||Bush monkeyflower||Shrub||4||3||2||1||Planted in shade. Leaves and growth look good, but waiting for flowers|
|Mimulus aurantiacus||Bush monkeyflower var ?||Shrub||4||1||3||1||A lower, spreading mimulus. Leaves and growth look good, but waiting for flowers. Doubled in size after Spring rain|
|Nandina domestica||Heavenly bamboo||Shrub||5||2||3-4||1||Leaves look healthy.|
|Oxalis pes-caprae||Sourgrass||Herb||5||1||2-4||1-2||Under dripline. It’s invasive, but in the spirit of permaculture I’m trying to learn from it. Makes me want to try a native oxalis like Oxalis oregana|
|Pittosporum eugenioides||Tarata||Low tree||5||1||2||1||Predates me. Healthy. Looks like a volunteer.|
|Pittosporum tobira||Mock orange||Low tree||5||3||5||1||Flowering and leaves look good|
|Prunus cerasifera||Purple leaf ornamental plum||Low tree||3||1||3||1||I think this is a plum. The tree leaves regularly, but hasn’t flowered and has dying branches. Suspect it was planted when the walnut was smaller and let more light through. Arborist advised removal due to ill health.|
|Plantago subnuda||Tall coastal plantain||Herb||1||2||2||New planting🤞 Slug favorite.|
|Rudbeckia californica||California coneflower||Shrub||5||1||4||1||Planted in a pot (away from slugs) but in range of leaf fall|
|Stachys bullata||Wood mint||Herb||1||2||2||New planting🤞 Juglone-tolerant per 2. Slow growing. Spring rain didn’t improve. Suspect more sun needed.|
|Symphyotrichum chilense||California aster||Shrub||4||3||3||1||Leaves look good, slow growing. Suspect more sun needed.|
|Taraxacum officinale||Dandelion||Herb||5||1||3||1||Self-propagating. Leaves look good. If it flowers and spreads, I’ll increase the health grade to 5|
* Numeric ranges:
- Health: 1-5, 5 = thriving
- Proximity: 1-3, 1 = planted inside dripline of walnut
- Sun: 1-5, 5 = planted in full sun
- Water: 1-3, 3 = planted in wet soil