Finding a Southern California plant that’s not in the ‘Sunset Western Garden Book’

I can’t deny that one of my most pleasurable experiences is discovering a plant in my neighborhood that is not included in the “Sunset Western Garden Book,” widely considered to be the gardeners’ bible throughout the West. I leap at the opportunity to share a plant species with readers that they might not know about. It’s also an opportunity for me, of course, to engage in a horticultural exploration, knowing not where it may lead and which secrets – botanical or otherwise – may be uncovered.  

For about a week, I had been driving by a row of trees growing in the parkway opposite the Van Nuys  –  Sherman Oaks Park on Hazeltine Avenue, just north of Huston Street in Sherman Oaks. I was surprised at what I saw since the only trees I knew that looked like these had stopped blooming several months ago. Still, maybe they had a reason for blooming late and I thought they might be sweetshade (Hymenosperum flavum) after all. Sweetshade has a decidedly vertical growth habit with yellow flowers and so did this tree spotted in the parkway. So the other day I stopped and got out of the car to take a closer look. Immediately, I knew these trees were not sweetshade, a tree named for its flowers’ mellifluous fragrance. 

The flowers of these trees are bereft of fragrance although they are far more opulent than sweetshade blooms. Each flower consists of five ruffled petals fused at their base, while clusters of flowers develop on branch tips. In time, foot-long seed pods hanging ornamentally in twisted clusters will form and remain on the tree until next year’s crop of flowers. This is an excellent street tree, courtyard tree, or candidate for a screen along a property line since it grows relatively quickly to a height of no more than 30 feet. It is hardy down to 25 degrees and pest-free. In the 1940s, it was planted as a street tree in Santa Barbara but somehow fell off the map where its usefulness in this capacity is concerned. In more than 40 years of local plant watching, I had never seen it anywhere.

Native to East Africa, it goes by the name of Nile tulip tree (Markhamia lutea). The genus name honors Robert Markham, who famously brought the cinchona tree to India; its bark, containing quinine, would provide a local source of that compound for the treatment of malaria. The Nile tulip tree itself has an age-old legacy in Uganda, where its leaves, roots, and bark are the source of medicine for ailments of every description. Incidentally, I identified the Nile tulip tree through Pl@ntNet (identify.plantnet.org). To the best of my knowledge, it is the only plant identity app that is entirely free.

The African tulip tree (Spathodea campanulata) is a related species with large tulip-shaped flowers in reddish orange. This tree grows larger than Nile tulip tree with less cold tolerance. You can find an outstanding specimen at the Los Angeles Zoo and another on the north side of Venice Boulevard just west of Barrington Avenue in Mar Vista. However, planting it in the San Fernando Valley and points north is not advisable due to its sensitivity to frost. By the way, there is a yellow African tulip tree (Spathodea campanula var. Lutea) as well, and all three tulip trees are available through retail nurseries supplied by San Marcos Growers (smgrowers.com).

When it comes to flowering trees and vines, there is no family like Bignoniaceae, whose members include not only tulip trees but jacarandas, catalpa trees, and the native desert willow (Chilopsis linearis). There are vine species that bloom in spring such as lavender trumpet vine (Clytostoma callistegioides), but most come into their own in hotter weather, although at least one winter bloomer (see below) is highly worth planting.

Indeed, bignonia vines, also known as crossvines, are hard to resist, flowering this time of year in yellow, pink, red and all sorts of oranges. They are excellent choices for covering a chainlink fence. If you are thinking about plant selections for a wildlife-friendly garden, look no further than bignonias, to which hummingbirds and butterflies are helplessly attracted.  

Their most outstanding representatives bloom in orange. One is Bignonia capreolata ‘Tangerine Beauty,’ flowering both now and in the spring. Another is esperanza (Tecoma stans) that is grown not only as a vine, but as a stand-alone shrub, or small tree; it is also ideal for an evergreen flowering hedge, blooming from spring until fall. The most spectacular winter-flowering plant I have ever seen (another crossvine) erupts in orange, but you will probably need to live close to the ocean or in south Orange County to grow it successfully due to its sensitivity to frost. The plant is called flame vine (Pyrostegia venusta) and blooms from fall until spring. It is evergreen and climbs to 40 feet. Flame vine is one of a small group of plants whose flowers make a more stunning impact when they are closed than when they are open. A flame vine’s flower show is most aptly described as “fireworks finale in flaming orange.” 

One orange bignonia you want to plant with caution is cape honeysuckle (Tecoma capensis). This is a plant from South Africa’s Cape of Good Hope region that spreads without conscience due to intense suckering and aggressive root growth. It is outstanding for erosion control on problematic soil or where there is wind or salty ocean spray, but it must be planted alone with plenty of room to roam since it will smother every other piece of vegetation in its vicinity. It is usually seen blooming in orange but a yellow variety is also encountered now and then.

Following a recent column on water ponds, I received the following email from Grace Hampton who gardens in Burbank: “Years ago, I built a water pond and planted water lilies and cattail, water hyacinth, and water iris, to name a few. I noticed it attracted beautiful insects such as damsel flies. I got a lot of enjoyment out of watching the flowers bloom and the goldfish spawn. Then the raccoons came and ripped up the plants and got the goldfish. I found that the easiest plant to grow was water hyacinth. All you need is anything that will hold water. Put topsoil on the bottom, fill it with water and place the plant on top. It will multiply rapidly and will need to be thinned out.” Water hyacinth (EIchhornia crassipes) has gorgeous violet flowers yet it will be a problem where you have a pond with a number of plant species you wish to grow since it will quickly smother everything. However, if you want to grow it by itself, you will admire its non-stop floriferous presence. The water iris Hampton mentions occurs in several colors and goes by the name of blue flag (Iris versicolor), yellow flag (Iris pseudacorus), copper iris (Irish fulva), depending on the species. These irises can be planted in the middle of a pond, along the edge, or in any soil that stays reasonably moist.

There will be a begonia show and sale at Sherman Library & Gardens in Corona Del Mar on September 21 & 22 and a chrysanthemum show on October 26 & 27. For more information, go to thesherman.org or call (949) 673-2261.

California native of the week: I have perennial California poppies (Eschscholzia california) blooming now whose flowers are yellow. Upon investigating the subject of orange versus yellow California poppies, it appears that annual poppies are typically orange and occasionally yellow, while those of perennial California poppies are invariably yellow. However, my yellow perennial poppies are offspring of the orange poppies I planted a number of years ago, so it would appear that the perennial version may be birthed by the much more common annual version. For several years I saw nothing but orange poppies but for the last few years, perennial yellow ones are also on display. The habitat of California poppies is extensive, stretching from southern Washington to Baja California. The Silver Falls Seed Company (silvertonfallsseeds.com) in Silverton, located in western Oregon, makes this rather bold assertion: “The perennial California poppy is the low-growing coastal form of the California poppy and is native to the Northwest region. Rather than the more common orange color, the perennial California poppy is predominantly yellow and sometimes is slightly orange in the center. The foliage has a blue-gray hue to it.” Needless to say, I was amazed to see that the flower adjoining this text was identical to that growing on my perennial poppy. I have yet to unravel this mystery but would be curious if anyone reading this has had a similar experience with annual orange California poppies whose progeny, at some point, developed into perennials with yellow flowers. Tufted California poppies (Eschscholzia caespitosa and Eschscholzia lobbii) produce pure yellow flowers exclusively. Seeds of California poppies in other colors – red, pink, magenta, and white – are widely available through Internet vendors. You can scatter California poppy seeds now or later but leave them bare, never covered with soil or mulch.

If you have a seldom seen plant you would like to tell readers about, please email your experience with it to joshua@perfectplants.com.  Your questions and comments, as well garden challenges, conundrums, and success stories are always welcome.