San Diego Management & Monitoring Program


Dehesa nolina
Nolina interrata


Kingdom Phylum Subphylum Class Order Suborder Family

Current distribution rangewide

Restricted distribution in southern foothills of San Diego County and northwest Baja California [1). In Baja, three small populations reported between border and Ensenada. Elevation range 230-700m [2). In San Diego, Reiser (1994) reported from Dehesa School, McGinty Peak; Sequan Peak; also Barber Mountain, Jamul Butte, Wood Valley, Pat's Mountain, and on west side of Sloane Canyon on The Mesa. In the MSPA, occurs in MU3 (McGinty Mountain Preserve, San Diego National Wildlife Refuge, South Crest Properties, Sycuan Peak Ecological Reserve; [4]).


List status

SE; Proposed for federal listing


Habitat affinities

Typically found in rugged terrain dominated by southern mixed chaparral or chamise chaparral in areas with these nutrient poor clay soils [1,3]. Known only from gabbro substrates (rich in ferro-magnesium minerals; [2]).


Taxonomy and genetics

Perennial herb; Ruscaceae family [6]. Dice (1988) concluded N. interrata distinct from Parry’s beargrass (N. parryi), Peninsular beargrass (N.cismontana), and Bigelow’s nolina (N. bigelovii) and N. wolfii (N. wolfii reduced to synonomy with N. parryi); referred to these as N. bigelovii- N. parryi complex. Distinguished from the other Nolina in California by lack of aerial stems, rosettes with 45 or fewer finely serrate leaves, flower stalks under 1.6 m tall; distinguished from Yucca species by lack of a rigid spinose (spiny) leaf tip and leaves with shredding margins [1].


Life history demography

Forms clusters of rosettes and has flower stalks up to 1.6 m tall [1]. Reproduces sexually and asexually (from underground stems; [1]). Nolina can take long period from germination to attain sufficient size for flowering, although two male plants of this species flowered in 3 years or less based on collected seeds [2]. Flowers profusely after fires [1]. Population estimated at ~9,000 plants within the 15.6 km2 range in the U.S. [1]. Morphology helps survival during fire (subterranean buds and above-ground apical buds protected by dense crown of overlapping succulent leaf bases); mass-flowering events observed 1-2 years following fire, although seed predation may diminish productivity from these events [2].


Seasonal phenology

Blooming period June-July [6].


Pollination seed dispersal

Dioecious (separate male and female plants); does not flower every year; asexual reproduction may compensate for this [1]. Insect visitors to the N. bigelovii- N. parryi complex primarily bees (honey bees, solitary native bees; [2]). Seeds disseminated by disarticulation of pedicel, with wind and rains presumed to aid in the process. Seedling recruitment in N. bigelovii- N. parryi complex considered rare due to seed predation [2].


Threats

Fire suppression leading to fuels accumulation increases vulnerability to fire because of increased fire intensity leading to increased risk of mortality and seed bank destruction [1]. Frequent fire can prevent plants from reaching reproductive maturity. Threatened by residential development, vehicles, altered fire regimes, and horticultural collecting; possibly threatened by non-native plants [6].


Special considerations:

Because of affinity for clay soils, often associated with other rare plant species [1]. Dice (1988) notes population sizes may have been overstated in some instances; provides an example of a small population with 2000 rosettes he estimated to represent 50 individuals based on counting discrete clusters of rosettes separated by at least 0.5m, but in a preliminary genetic analysis found each cluster was genetically identical at 15 loci.


Dehesa nolina sources