BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Juglans californica | Southern California Walnut 



GENERAL BOTANICAL CHARACTERISTICS : 
Southern California walnut is a native, deciduous tree that grows from
20 to 49 feet (6-15 m) tall [15,21].  It varies considerably in
morphology according to the age of the tree and site characteristics.
Trees in savanna woodland tend to have multiple trunks which grow
outward from a ring at the base, giving younger trees the appearance of
"V"-shaped shrubs.  Trees in more dense stands tend to be single-stemmed
and taller [13,25].  The strongly scented trunk is blackish brown and
becomes deeply furrowed with age [15].  The root system is extensive,
often with a deep taproot [11].  The leaves are 1.5 to 3 inches (3.5-7.5
cm) long [15].  Southern California walnut trees live to be about 100
years old [11].

Southern California walnut is monoecious [15,21].  Slender staminate
catkins develop on the wood of the previous year.  Pistillate flowers
are borne singly or in clusters in short terminal spikes on the current
year's growth [4].  The globose fruit is  contained in an indehiscent
husk or shell that does not open at maturity [4,15].  


RAUNKIAER LIFE FORM : 
   Phanerophyte


REGENERATION PROCESSES : 
Sexual reproduction:  Southern California walnut produces seed at 5 to 8
years of age [4].  Variations in precipitation from year to year can
affect fruit production and seedling establishment.  In drought years
little or no fruit is produced [13].  Seeds do not have a dormancy
period and usually germinate within 4 weeks of dispersal [4,13].  In the
spring in the San Jose Hills, densities of 4,742 seedlings per acre
(2,000/ha) have been reported [25].  The western gray squirrel may be an
important dispersal agent for walnut seed [25].

Vegetative reproduction:  Southern California walnut sprouts from the
root crown and trunk following cutting or burning [25,29].  


SITE CHARACTERISTICS : 
Southern California walnut occurs in a mediterranean climate,
characterized by mild, wet winters and hot, dry summers [12].  Trees
generally occur on mesic sites such as north slopes, creekbeds, canyon
bottoms, and alluvial terraces [5,19,25].  Trees grow best in deep,
alluvial soils with high water-holding capacity.  Soils are high in
clay content [10,25].  At California State Polytechnic University, soils
beneath walnut forests are 3.3 feet (1 m) deep [25].

Elevation:  Although southern California walnut has been successfully
planted at elevations up to 3,500 feet (1,066 m), it usually occurs from
500 to 2,500 feet (150-760 m) elevation [1,25].



SUCCESSIONAL STATUS : 
NO-ENTRY


SEASONAL DEVELOPMENT : 
Southern California walnut leaves appear in January and February, with
all trees in full leaf by March [25].  Trees on warmer or drier sites
develop leaves several weeks earlier than those in cooler, more mesic
locations.  Flowering begins about the same time as leaf production,
with fruits developing to full size during spring.  By late summer
fruits have matured.  Fruit abscission begins in October and November,
but some fruits remain on the tree throughout winter [25].
  

Related categories for Species: Juglans californica | Southern California Walnut