Juglans californica. Southern California Black Walnut.
Since moving to my current home I’ve been wanting to plant one of these trees. Southern California black walnut is a small tree (most sources give it a height between 20 to 30 feet), perfect for the smaller yards of the urban landscape. Its natural range includes almost all of the Los Angeles basin, though its existence as a wild plant is threaten by urban development. The walnuts it grows are smaller than the store bought nuts and harder to get to. But they are attractive to birds, especially jays, and squirrels. The Southern California Black Walnut tree is a great choice for a habitat garden. It is written that the tree is strongly allelopathic, limiting the growth of any nearby or understory plants. Yet, the few Juglans I’ve seen growing naturally were in densely vegetated areas.
But it is not an easy plant to purchase.
When I landscaped my front yard, I was thinking of using a Southern California Black Walnut as a centerpiece. It would be unique for the neighborhood and its small size wouldn’t obscure the view from the second floor. But as I checked the inventory of the native plant nurseries around Southern California, none had the plant in stock. I could have waited, but I am not a patient gardener. I want my plants now! So instead, I planted a Louis Edmunds manzanita (Arctostaphylos bakeri ‘Louis Edmunds’), an upright manzanita reaching up to ten feet in height. Ironically, manzanita is a slow grower so it will be a few years before it reaches ten feet. Perhaps a tall ceanothus – a fast grower for the impatient gardener – would have been a better choice.
This Fall, after having our backyard torn up to build my wife’s dream swimming pool, I ended up with the back third of the yard for me to play with. So my search for a Southern California black walnut was renewed. And again, it was being an elusive item. But there was much more to be done.
The last third of my backyard is a downward slope, about twenty by sixty feet and dropping as much as ten feet, giving our yard a view of our neighborhood and sunsets. Till now I haven’t done much with the slope. The soil was clay with a lot of grit which can make it feel like I’m walking on ballbearings. It was hard to maneuver around the slope. And to top it off, the dirt was trash, quite literally trash. Broken pieces of concrete, small and large, help make up the soil, and any shovelful of dirt had some broken glass in it. I found old toys, crushed up beer cans, and soda pop bottles from long gone soda companies. Lots of broken bathroom tiles and rusted pieces of metal. Each time I dug it was an archeological dig.
On one side of the slope I did plant a toyon (Heteromeles arbutifolia) and then tossed a couple of handfuls of California poppy (Eschscholzia californica) seeds. That was in the winter of 2018. My little one foot toyon is now a lanky twelve feet high and the poppies resow themselves each year, claiming more and more of my yard. Not that I’m complaining.
Besides that I weeded. A lot. I have no idea when this slope was last regularly maintained and so I had decades of weeds to contend with. But the poppies helped suppress them and when they bloomed, I had my own personal superbloom. But I held off doing more, till we put in some hardscape to help make the hill manageable.
There was another native I had planted near the bottom of the slope that deserves special recognition for hardiness above and beyond the call of duty. Last winter before pool construction, I planted an island malva (Malva assurgentiflora) at the base of the slope. Not a local native, island malva is found off the Southern California coast on the Channel Islands, though escapees from gardens have naturalized along the coast. I figure where I planted it would keep it safe from any harm from the construction. I was wrong. The poor plant got partially buried a couple of time, had old pipes and lumber tossed on it, had a chuck of its roots dug out so concrete could be poured for a railing post, and was covered in thick coat of dust. I kept digging it out and watering it but it looked grim. It survived though and is thriving, which is a miracle.
In the process of building the pool, we had hardscaping done on the hillside, adding retaining walls and a couple of paths that transversed the slope. The paths joined and lead to the lowest corner where a brick patio was built for a little meditation area. Now with all that was done, I could go to work.
For the most part, I wanted to focus on plants that were native to Baldwin Hills, where I live, and the surrounding LA basin, but I wasn’t going to be dogmatic about it. If a few species originated from the Channel Islands or Central California, they wouldn’t be too out of place. That is always the question when planting a native garden, isn’t it? How native is it going to be? If I wanted to be open to all California natives I could have planted a nice mixed grove of redwoods and Joshua trees – two iconic California natives that are found hundreds of miles apart – one from the coastal rainforests of Northern California, the other from the high deserts of Southern California. It would have made for an interesting watering challenge.
Keeping local meant my focus would be the coastal scrub sage that once covered most of coastal Southern California along with the surrounding chaparral. These plants are already adapted for the soil and climate of the area. For my starting point, I looked to Kenneth Hahn State Recreation Area. The park is a little gem located in the Baldwin Hills. A large portion of Kenneth Hahn SRA is undeveloped and contains remnants of the coastal scrub sage that once grew in this area. Though heavily degraded with a large number of invasive plants, it does provide an indication of what some of the most common plants in my neighborhood would have been. By using plants native to my region, habitat area for local wildlife increases, and, maybe, some of the damage down by urban development is turned back.
Some plant choices were obvious. The toyon already fitted in, found on most of the natural hillsides around Los Angeles. This local is a large evergreen shrub with dark green leaves with serrated edges. Summertime clusters of small white flowers bloom in profusion. Once pollinated, the flowers slowly mature through Autumn into bright red bunches of berries giving toyon one of its other common names, Christmas berry. The berries provides food for the birds.
Two other signature plants of the coastal sage scrub found in Kenneth Hahn SRA are sagebrush and buckwheat. California sagebrush (Artemisia californica) is one of the signature plants of the coastal sage scrub. A billowy plant covered with feathery leaves, it begs the passerby to run their fingers through it. Do so and enjoy the deep aroma it leaves on your skin. As Spring warms up and turns to Summer, it drops its longer leaves, replaced by smaller, more drought resistant leaves. Some of the sagebrushes will become a slivery white, others a muted green. Still others in the height of summer drop all their leaves and enter dormancy. In the garden, a little summer water can help prevent that. But out on its own, California sagebrush can appear dead and lifeless in the hot days of August and September. But come the cooler Autumn nights and the first rains, it miraculously rises back into life.
Buckwheat also is a common plant found in the coastal scrub sage as well as in most other California climates from desert to high mountains. California buckwheat (Eriogonum fasciculatum) is a common and widespread species, equally at home on the coastline as in the desert. Its green needle-like leaves help conserve moisture. As summer approaches, long, narrow stalks grow, branching out at the top, bearing clusters of pinkish-white flowers. The flowers are only millimeters wide, but together they form pom-poms up to an inch or two wide. Butterflies and bees come far and wide for the nectar.
Many species of buckwheat are found in California in a variety of colors of both leaf and flower. I have California buckwheat lining one side of a downhill path with ashyleaf buckwheat (Eriogonum cinereum) along the other side. Both plants can be found growing in the Los Angeles basin. They are medium size brushes, growing up to 4 – 6 feet in height and width. At first glance it would be hard to see they are related. Instead of needle-like leaves, ashyleaf has larger leaves, each oval about an inch long. The new leaves are a dull green coated with fine white hairs giving them an ashy coloring becoming a darker green as they mature. Once both buckwheats bloom though their relation to each other is quickly exposed with the flowers being very similar in both form and color.
The complex patterns of climate, terrain, and soil types in California can result in wide variety of different species from the same genus. Buckwheat is one such genus. Two other buckwheats planted in my garden are found naturally in a very limited range. Red-flowered buckwheat (Eriogonum grande var. rubescens) can be found only on the northern Channel Islands. Conejo buckwheat (Eriogonum crocatum) is limited to a small area on the southern edge of Ventura county. Though they live outside the Los Angeles basin, they are still natives of the coastal scrub sage.
Red-flowered buckwheat has a similar leaf shape to ashyleaf, though the top of the leaf is a solid dark green with the underside almost white. It is a small plant getting only two feet high at most and three feet wide. Again, the flower structure gives away it relation to other buckwheats but the color is a striking reddish-pink.
Conejo Buckwheat has fuzzy, crinkly whitish leaves with bright pom-poms of yellow flowers. As with many of the buckwheats, the stalks and flowers dry to a dark brown and provide a striking contrast to the white leaves. There are several other species of native buckwheat useful for the garden as well as a wealth of species found growing wild through out California from the sunny coast up to cool alpine mountain tops.
Another genus of plants found throughout California and coming in a wide variety of species is the ceanothus. Along with the toyon, it’s one of my favorite native plants. No native California garden should be without a ceanothus. The ceanothus has dark green leathery leaves year around, but it is its flowering that makes it spectacular. The flowers are minuscule forming oblong clusters like small lilacs ( a common name for ceanothus is California lilac). The color ranges from a pale white to a dark bluish violet. With species ranging to low growing ground cover to small trees; there is a ceanothus that can work in any yard.
Ceanothus are not common in the coastal scrub sage but are more prominent in the chaparral growing on the mountainsides surrounding Los Angeles. My original goal was to plant one of the ceanothus species found in the LA mountains. But there were a couple of challenges. First, most ceanothus prefer fast draining, gravelly soil, not the clay of my yard. And second, the native ceanothus in my area grow into rather large shrubs – ten to twenty feet wide and high. With our hillside view, planting something that will block it will earn me a very disapproving look from my wife.
There was one possible candidate – greenbark ceanothus (Ceanothus spinosus), which may have even been a common plant in Kenneth Hahn SRA before European settlement. Greenbark ceanothus did have a potential of reaching ten feet high, however, ceanothus can handle light pruning so by being diligent, the height can be kept low. Some sources indicated it could handle clay soil. While it is available in the native plant trade, I had no luck finding it. So I ended up looking further afield and settled on Ceanothus ‘Concha’ (again, that impatience thing kicking in). Concha is a hybrid of two species of ceanothus found in Central California. More of a mid-size shrub, it tops out around six feet high – low enough to not block our view. Flower-wise, it is hard to beat Concha with its stunning deep blue flowers attracting all types of pollinators.
Where as some plants have a very limited range, needing very precise conditions, bladderpod (Peritoma arborea) is a hardy native found in wide swath in Southern California. I’ve seen it growing on cool, windy ocean bluffs though it is also found in the hot low deserts. A mid-size shrub with pale green leaves, it sports bright yellow flowers. The plant leaves are aromatic but there is debate about whether it’s a pleasant or unpleasant odor. I don’t have the greatest sense of smell, but to me it smells like a cross between bell peppers and onions. The name comes from its fruits – a ballon like capsule with seeds within. With the sun behind them, the pods appear a little transparent. It is said the seedpod and seeds are edible.
Meanwhile, the search for a Southern California Black Walnut continued. Our pool and landscape designer Nysha (Ardenwoods Landscape Design) was helping with the search, reaching out to her wholesales nursery contacts. No luck, but I wasn’t going to give up. Scrolling through the website of a small gardening shop featuring California natives, there is was. Juglans californica. They had one left, in a tree pot, which, at the time, I had no idea what that was. In these pandemic times, I purchased it on-line and quickly got an e-mail saying it was ready for pick up.
In general, when purchasing California natives, smaller is often better. A younger plant in a one gallon container is often more adaptable to being planted in the ground than a plant in a five gallon container. The smaller plants are quicker at getting their roots established in the surrounding soil and and in a year or two catch up to the size of the plants from larger containers. However, small is small. A newly planted yard of native plants usually feature a lot of empty space and give the impression of being underplanted. When I plant a little twig that is suppose to be a large shrub, I get some sideways looks from my wife. She and our landscape designer pushed for getting plants in five gallon containers so the new yard will look good from the start.
When I got to the garden shop to pick up the walnut tree, I could just hear the snickering in my head. The tree pot is a 4” pot that is almost a foot deep. The walnut tree itself was a ten inch stick with a few scraggily half-dead leaves. Charlie Brown couldn’t have done better. I was a little concerned about how the tree looked, but walnut trees are deciduous so I knew it would be entering a dormant state. Giving the impression of a robust tree though, it did not.
So the Charlie Brown tree got a few laughs, but I planted it on my hill on the side where the neighbors’ trees already blocked our view. All it needed was love, and for the days to get longer and warmer. Within a few weeks all its leaves were dead and its appearance as a dead stick was complete. My wife kept asking if it died, and I kept telling her (and myself) it is just dormant. Once it warms up, it’ll turn green. I hope. Sometimes gardening requires blind faith.
Since walnut trees are allelopathic, I wanted to get the understory plants established before they have to contend with any toxins leached from the tree’s litter. Near the tree I planted sticky leaf monkey flower (Diplacus longiflorus). This small shrub is common throughout the Los Angeles region, providing splashes of pastel orange on the hillsides in the Spring. Growing up to three feet wide and high in size, it will also provide some shade for the walnut seedling.
While orange is the most common color, the flowers can range from yellow to red. It is called sticky leaf because the leaves and stems are, well, kind of sticky. Why it is called monkey flower no one really knows as the flowers neither look like monkeys or attract monkeys. Monkey flowers prefers quick draining soils, which I do not have. However, I have seen sticky monkey flower growing wild in Kenneth Hahn SRA where the hillsides, like mine, are clay. So I figure to take a chance and see how the plant does in my yard.
Down the slope from the walnut I planted hollyleaf redberry (Rhamnus ilicifolia), a spreading shrub that will help protect the hillside from erosion. In many of my plant choices, erosion control was a consideration, especially since my hillside after all the landscaping was covered in loose soil. Shrubs like the hollyleaf redberry can help in a couple of ways. Their extensive roots help hold the soil in place while their canopy of leaves will slow down the falling rain so it doesn’t pound the soil.
The redberry looked a bit better than the walnut tree. Mainly a stick growing sideways with a few leaves at the end and a couple at the base. Luckily, the redberry isn’t winter dormant and within a few weeks new leaves began appearing. And hidden among the leaves were its flowers. The plant description lists the flowers as being inconspicuous. And that they are. Only a few millimeters wide and colored a pale yellow-green, they would never be noticed by a casual passerby. Hopefully, the flowers will develop into more conspicuous red berries.
The plan is for the hollyleaf redberry to grow into a wide bush of medium height. But its mature size is listed as 3 – 10’ wide and 3 – 10’ high. When planting native plants it is important to keep size information in mind, but how do you plan when the range is from 3 feet to 10 feet? Most plants have a smaller difference in possible size – perhaps 8 – 10 feet, or 3 – 4 feet. Of course, adding to the challenge is the small size of the plant when first planted. It can be hard to picture it at full size while in a one gallon pot. My general rule when planting a plant with a wide range of potential size is that it will grow to whatever size I didn’t plan for.
Not a fast growing plant, I’ll have a lot of open ground around the redberry for awhile, and if it only grows to 3 feet a lot of remaining empty space. To help fill in the space, I have two strategies. One is to plant short lived perennials to fill in the space as the main plant grows. Here I planted three Great Valley gumplants (Grindelia camporum). Arising from a leafy rosette, these plants will also provide yellow daisy-like flowers. Contrasting to the cheerful flowers, the head of the flower is a spiky bulge.
Sowing wildflower is another way to fill in the spaces between the perennials. The California poppies I sowed on the hillside happily reseed themselves each year. I was worried after all the landscaping we had done with the excess dirt dumped on the hillside no poppies would come up. There was no need to worry. With the first rains, the poppies’ first leaves, cotyledons, appeared like two green snake tongues. I actually had to pull up some of the poppies that crowded the new plants. It will be another spectacular bloom this year.
I also sowed three other wildflowers, winecup clarkia (Clarkia purpurea), globe gilia (Gilia capitata), and tidy tips (Layia platyglossa). In a previous garden, I’ve had success with elegant clarkia (Clarkia unguiculata), but this time went with winecup clarkia as they are local natives. Globe gilia is another local with delicate blue flowers clustered in little balls. I found gilia’s make good cut flowers for a small vase.
And tidy tips, I can only hope for the best. I sowed these before at my old home only to have bugs eat all the seedlings. With the hillside being mostly exposed dirt with sparse plant litter for bugs to hide under I was hoping for better luck. Little seedlings soon broke through the soil only to disappear over the next two weeks. The two culprits I suspect are earwigs and house crickets – neither native to California. I wondered about these insects impact. Widespread through urban and suburban areas, what are their affect on remaining populations of tidy tips and other wildflowers that border cultivated yards and gardens? Luckily, three or four plants survived and are growing. It seems once the seedlings start getting bigger, the tidy tips leaves become less palatable to the bugs. So maybe I’ll finally get some tidy tips.
I also sowed some native clover. Mostly when one thinks of clover, the varieties that appear in lawns and playgrounds come to mind. I didn’t realize there were native clovers in California but there are quite a few. For some of the Native American tribes in California, clover was actually an important part of their diet. I’m still waiting to see how successful I am with the clover. Some of have sprouted, along with some non-native clovers. They all start out looking very much the same so it is hard to know what is a weed and what is a native at first. And bugs have been munching on them too. Stupid bugs.
But the exciting thing about clover, native or non-native, is they help improve the soil. Nitrogen is an important soil nutrient for plants, however, they are unable to use nitrogen in the atmosphere. In nutrient poor soils, clovers have a symbiotic relationship with bacteria that grows on their roots. As the plants ‘breath’ in, the nitrogen in the atmosphere is taken by the bacteria converting it into a form that can be used by the plant. Even after the clover dies, the nitrogen remains in the ground for other plants to use. For my trash filled dirt, a little extra nitrogen will be good.
On the other side of the yard, near the toyon, the hillside is steep and is when heavy rainfall comes, the run off from the yard flows down here. This is also where my dog likes to go up and down and dig his holes so I had to find some plants that could be trampled by him and also help with erosion. California goldenrod (Solidago velutina ssp. californica), Canyon Prince wild rye (Elymus condensatus ‘Canyon Prince’), and clustered field sedge (Carex praegracilis) are my three-prong attack.
California goldenrod send up leafy stalks two to three feet high that in late summer bear yellow flowers when most other plants are done flowering. Once established, they start spreading out via rhizomes, creating a thick patch. In a more formal garden, this can be problematic, but on an open hillside their dense, spreading nature will be an effective barrier slowing rain runoff and holding the soil in place. Since each stalk rises directly from the ground, if the dog runs through some of the patch, the plant will survive. That is, once the plant gets established. Right now I have some barriers around the plants so they can get a good start.
Canyon Prince wild rye (Elymus condensatus ‘Canyon Prince’) is a cultivar of giant wild rye (Elymus condensatus). Giant wild rye can be found in most open areas around LA. A tall grass with seedheads on ten feet high stalks. Canyon Prince is a more compact cultivar of giant wild rye that were originally found on the Channel Islands and a little more ideal for the garden. Canyon Prince grows in a dense bunch up to two feet high that will slowly spread wider making it effective for holding soil in place.
Clustered field sedge is a grass-like plant that also spreads, forming dense patches. Unlike the wild rye or goldenrod, it tends to want more water and isn’t considered drought tolerant. I planted it near the bottom of the hill that gets little sun in winter with soil that stays wet from the first rains to mid-spring. From then, this slope goes from part shade to full sun. I’m hoping the sedge will establish deep roots during the wet season to help during the dry season. I will water the hillside through the summer, but with most of my plants being drought tolerant, the sedge will have to do with minimal water. I expect it will go dormant by mid-summer fading to brown with some green remaining. As Autumn begins, I’ll give it a good haircut and the field sedge will send up new blades with the first rains.
It’s been a couple of months since I did most of the planting and the plants are taking root and starting to produce new growth. I’m out there everyday checking for any signs of problems, pulling any weeds I see while making sure not to pull the wildflower seedlings. Most of the slope is now covered by a thick green carpet of wildflowers. By March I expect the poppies to be in full bloom with the other wildflowers soon to follow. Many of the planted natives will also soon start blooming.
As for my Southern California black walnut, every day I check on it, often on my hands and knees looking for any sign of life. And then, I saw it. A speck. A tiny green speck. At the bottom of the trunk, in a crease a little above the ground, there it was: a brand new, never before seen green speck! Never has there been a prettier speck.
The walnut is alive! Alive!
Written and photographed by Alan Starbuck
For any native plant nerds out there, here is a list of the California natives I used in my backyard:
Species native to the Los Angeles basin:
- Acmispon glaber (Deerweed)
- Artemisia californica (California Sagebrush)
- Artemisia californica ‘Canyon Grey’ (Canyon Grey California Sagebrush)
- Carex praegracilis (Clustered Field Sedge)
- Clarkia purpurea (Winecup Clarkia)
- Diplacus longiflorus (Sticky Leaf Monkeyflower)
- Elymus condensatus ‘Canyon Prince’ (Canyon Prince Giant Wild Rye) – cultivar from Channel Islands
- Eriogonum cinereum (Ashyleaf Buckwheat)
- Eriogonum fasciculatum (California Buckwheat)
- Eriogonum fasciculatum ‘Wild Cascade’ (Wild Cascade California Buckwheat)
- Eschscholzia californica (California poppy)
- Gilia capitata (Globe Gilia)
- Grindelia camporum (Great Valley Gumplant)
- Heteromeles arbutifolia (Toyon)
- Juglans californica (Southern California Black Walnut)
- Layia platyglossa (Tidy Tips)
- Peritoma arborea (Bladderpod)
- Salvia mellifera (Black Sage)
- Sisyrinchium bellum (Blue Eyed Grass)
- Solidago velutina ssp. californica (California Goldenrod)
- Trifolium ciliolatum (Foothill Clover)
- Trifolium willdenovii (Tomcat Clover)
Species native to the valleys and mountainsides surrounding Los Angeles:
- Adenostoma fasciculatum ‘Nicolas’ (Nicolas Chamise) – cultivar from Channel Islands
- Penstemon heterophyllus ‘Margarita BOP’ (Margarita BOP Foothill Penstemon) – cultivar is a hybrid
- Polystichum munitum (Western Sword Fern)
- Rhamnus ilicifolia (Hollyleaf Redberry)
- Umbellularia californica (California Bay)
Species native and endemic to the Channel Islands:
- Eriogonum grande var. rubescens (Red-flowered Buckwheat)
- Malva assurgentiflora (Island Malva)
Plants native to other regions in California:
- Ceanothus ‘Concha’ (Concha Ceanothus)
- Cinopodium douglasii (Yerba Buena)
- Dudleya edulis (Fingertips Dudleya)
- Eriogonum crocatum (Conejo Buckwheat)
- Juncus patens (Spreading Rush)
- Lewisia species (Mixed Cliff Maids)
- Symphyotrichum chilense ‘Point St. George’ (Point St. George Coast Aster)