Conserving Valley Oak Trees

Micke Grove Zoo is home to a small grove of heritage Valley Oak trees (Quercus lobata) that are about 80 to 100 years old. Valley Oaks are endemic to California’s Central Valley and are categorized as Near Threatened by the World Conservation Union. Valley oak woodlands have largely disappeared from the San Joaquin Valley and few pockets of natural oak woodlands remain. Micke Grove Zoo has launched THE VALLEY OAK CONSERVATION PROJECT which aims to restore the depleted natural oak woodland in the Shumway Oak Grove Regional Park. The zoo is also a member of the California Oak Coalition.

The Valley Oak Conservation Project goal is to restore the natural oak woodland inside Shumway Oak Grove Regional Park, by planting valley oak saplings in the denuded areas where oak trees have succumbed to severe drought during the years 2015/2016. Micke Grove Zoo staff and volunteers are participating in project activities, which include collecting fresh acorns, processing them for germination through stratification, maintaining a small tree nursery, and finally planting healthy saplings in Shumway Oak Grove Regional Park.

 

Valley oak trees have created a mini woodland in the Zoo's amphitheater area

Processing Micke Grove Zoo's Valley Oak Acorns for Germination

 

Valley oak acorns are long and perpendicular tapering from the cap to the tip

• Collection: Micke Grove Zoo’s valley oak trees drop acorns during the fall season every year. Zoo volunteer, Atticus Swanson was tasked with the job of collecting these acorns. The acorns were examined for holes, cracks or insect activity and the damaged ones discarded. The rest were placed in water to conduct a float test. While healthy acorns remained submerged, damaged acorns floated. The damaged acorns were discarded.

 

Healthy acorns collected after the water test

• Stratification: 25 healthy valley oak acorns were selected for stratification. They were placed in two sandwich bags filled with moistened top soil. The sandwich bags were then placed in a refrigerator for 60 days. The cold and moist environment helps to break dormancy allowing the pericarp to break down and the acorn to germinate

 

Acorns in sandwich bags filled with topsoil for stratification

• Potting: After 60 days the sandwich bags were opened. The acorns had begun to germinate. They were gently removed and planted in tree pots filled with top soil. The acorns will remain in the nursery until the saplings are old enough to be planted.

 

Each germinating acorn was planted separate tree pots filled with topsoil