Orcutt’s Goldenbush

Orcutt’s goldenbush is a small, evergreen shrub that blooms yellow in the late summer and early fall. It resembles goldenbush (Isocoma menziesii) and sawtooth goldenbush (Hazardia squarrosa). One difference is the flower head. Orcutt’s goldenbush has both disk and ray flowers (like a daisy), while the other two have only disk flowers.

A few years ago, Orcutt’s goldenbush existed in California as a single small population in Manchester Habitat Conservation Area, just north of San Elijo Lagoon. To reduce the risk of losing this population to fire or disease, seeds were collected, grown in a local nursery and the seedlings planted in nearby protected areas. Stonebridge Mesa, on the east end of the Reserve, received 156 seedlings. In 2012 only 46 plants survived, but many were blooming, and seedlings were found – happy signs of recruitment. We remain optimistic that the new population will survive.

Description ²

Orcutt’s goldenbush is a small, rounded, evergreen  shrub, usually three feet (1 m) or less in height. Branches are reddish. Green leaves have a tinge of olive color and both surfaces are resinous, giving them a lustrous sheen; the color and luster makes the plant easy to recognize from a distance. Leaves are 3/4 – 2 inches long (2 – 5 cm), obovate, with a sharp tip and smooth margins.

The yellow flowers are composite heads of two types of florets. There are 8-12 ray florets surrounding 10-20 disk florets. These compound flower heads are born in terminal and auxiliary clusters. Ray florets are female, with a two-branched pistil. Disk florets are bisexual with five stamens in a column around the pistil. Below each compound flower are numerous overlapping green, resinous phyllaries that are curved back at the tips. Flowers bloom primarily from June into October.¹

Seeds are about 1/8 inch long (3 – 4.5 mm), slim, each with a tawny pappus which disperses the seed in the wind. Dried petals often remain among the developing seeds, giving the seed head an old, unkempt appearance; it doesn’t invite wishing as a dandelion puff does.

Classification  

Orcutt’s goldenbush is a dicot angiosperm in the sunflower family, the Asteraceae.² This is the largest family of vascular plants in the Northern Hemisphere.¹⁴³ “Flowers” of Asteraceae are made up of one or both of two types of flowers (florets): symmetrical disk florets and strapped-shaped ray florets. These are crowded onto a common base (receptacle), and together are often assumed to be a single flower, which we call a flower head.^11,44,49

Other Asteraceae that commonly occur in the Reserve include bush sunflower (Encelia californica) and California sagebrush (Artemisia californica).

The genus Hazardia was formerly included within the large genus Haplopappus.¹⁸⁹ There is one other species of Hazardia, sawtooth goldenbush (H. squarossa) has been found in the Reserve.⁴⁸ The closely related goldenbush (Isocoma menziesii) is very common.

Ecology  

Little is known about the ecology, or general biology of Orcutt’s goldenbush.¹¹³

The very small size and restricted distribution of the single wild population in the United States makes it extremely vulnerable to any disturbance, although the success of the out-planted populations in nearby areas mitigates this somewhat. A newly recognized threat is the possibility that Orcutt’s goldenbush will lose its genetic identity because of hybridization with the related sawtooth goldenbush (H. squarossa).¹⁸⁷

Human Uses  

We have found no information about uses of Orcutt’s goldenbush.

Interesting Facts  

The only wild population of Orcutt’s goldenbush in the U.S. was a “vigorous population” discovered in Encinitas, CA in 1979, on land already approved for housing.¹⁹⁰ Prior to development, some plants were transplanted out of the proposed housing area; a population was established at the San Diego Botanic Garden.¹⁸⁸ Subsequent development in the original area reduced the remaining population by about half, and the population in 2012 was about 670 plants in an area less than five acres,^{113, 187} located within the protected Manchester Habitat Conservation Area. To guard against the loss of the entire population from a local catastrophe (especially wildfire), four additional, “experimental” populations were established in nearby protected areas from seeds of the wild plants. A second site was established in Manchester Habitat Conservation Area, and two sites in Carlsbad (Kelly Ranch and Rancho La Costa Habitat Conservation Area). The fourth population was planted in 2004 on the Stonebridge Mesa area of San Elijo Lagoon Ecological Reserve.

One hundred and fifty-six plants were established on Stonebridge Mesa.¹⁸⁷ By 2005, high initial mortality had reduced the population to 75 plants. In 2012 only 46 adults were found, but there were 18 seedlings. Although less than a third of the original plants have survived, many of these were – and still, are in 2015 – healthy and blooming. Hopefully, the presence of seedlings indicates the potential for long-term population reproduction and survival.