This Native Plant of the Month article was provided by Dan Songster, former President of the Orange County Chapter of the California Native Plant Society (OCCNPS).

• What: Isocoma menziesii (Coast Goldenbush, Menzies’ Goldenbush)
• Type: Evergreen Shrub
• Light: Full sun 
• Soil: Well drained (but adaptable to clay soils)
• Water: Drought tolerant
• Common Habitat: Coastal Sage Scrub, Southern grasslands

The Basics

Certainly more than meets the eye, this tough, easy to grow pollination machine is listed as a weed in some California state agricultural texts. Isocoma menziesii var. menziesii, (Coast Goldenbush), was known as Haplopappus venetus when I first became aquatinted with this very interesting plant.

A relatively common component of the Coastal Sage Scrub community, it ranges from northern Baja far up the coast in dune and bluff situations as well as conditions more consistent with our local concept of Coastal Sage Scrub. It is also found thriving in disturbed sites such as old road cuts and roadsides. 

A member of the huge Asteraceae family, this somewhat woody sub-shrub can be found erect, decumbent, and even prostrate in the wild (in fact there are several varieties now that reflect some of those differences).

In garden situations, Menzies’ Goldenbush is usually erect with bright green, often needle-like leaves. Its woody stems branching from the base terminate in dense golden-yellow flower clusters. These stems, (normally taller than the one-foot to three-foot range described in some references), often bend and sway in a breeze, adding motion to the garden. 

Garden Uses

Some gardeners appreciate this plant for its toughness and will put it in full sun where other natives may have (Gasp!) perished. Good! This is one plant that can take whatever you give it. I have also used it for its size to hide block walls or fences in the back of a garden bed. Simply realize that even with a fairly severe pruning in early winter it can still often reach 6 to 7 feet high and almost as wide, so give it room!

Some native design combinations could include the brilliant red California Fuchsia (also fall blooming). Consider pairing it with the silver foliage of Artemesia californica or the mounding habit and whip-like panicles of Muhlenbergia rigens as a background. The fragrant lavender-flowered, Verbena lilacina is a good foreground plant, especially when coupled with the bold gray of Dudleya pulverulenta or Artemesia pycnocephala.

Of course, Coast Goldenbush fits in nicely with the native grasslands along the coast, standing out with green foliage and golden flowers during the grass’s driest months. It is seldom the star in such ensembles, but adds depth to the mixture and a flowering season lasting into fall. 

Commonly used in restoration projects for its pollinator benefits, Menzies’ Goldenbush can be a key plant to use in your own habitat garden. I really like the broad collection of insects that visit the plant throughout its blooming period. I first noticed various metallic colored wasps (eating pollen?), numerous species of flies (many native), a few Spittle bugs camouflaged in their spittle (quite amazing), very colorful beetles (some politely nibbling, others downright devouring flowers), and of course, many species of small butterflies and skippers.

It is a host plant for pollinators like the white-lined sphinx, sunflower moth, orange tortrix moth and snakeweed borer. It is not unusual to have several insect species enjoying the plant simultaneously. This is a great eye-level classroom for the study of species interaction and dependence that would easily hold the interest of young school children–it certainly holds mine!

Care 

Coast Goldenbush is easy to grow, colorful in the hot fall months, and disease resistant. This is a very nice native plant indeed and one that does well in a broad range of soils (including clay).

Isocoma is at its best in full, direct sun. In natural situations it flowers for a month, but in gardens, flowering often exceeds two months duration when a bit of water is applied every two or three weeks. The plant does not seem to mind this treatment, (which often prompts root rot in some drought-conditioned natives).

In fact, I have noticed no serious problems with disease or pests. My only maintenance involves pruning the plant pretty hard in early to mid-winter to encourage fresh growth, and maybe keep it a bit smaller, but perhaps that is simply a personal preference.

Note 

In our wildlands, from a distance or when passing quickly, Isacoma menziesii (whether var menziesii, var. vernoniodes, or others), can be easily confused with some of its close relatives in the Asteraceae Family such as Hazardia (example: H. squarrosa). Besides all bearing rich yellow flowers, they are also generally summer to fall bloomers. If you wish to really examine the various closely related Asters, you can reference Bob Allen and Fred Robert’s book Wildflowers of Orange County and the Santa Ana Mountains.