Flax-leaved horseweed (Erigeron bonariensis)
Composite or sunflower family -- Asteraceae
September 1, 2015.  Mesa Trail
Color: White

Non-native

Peruvian pepper tree (Schinus molle)

Cashew or sumac family -- Anacardiaceae

August 9, 2015.  Upper Santa Rosa Trail

Tree

Non-native

Poison hemlock (Conium maculatum)

Carrot or parsley family -- Apiaceae

July 8, 2015.  Upper Santa Rosa Trail

Non-native

Purple rock rose or orchid rock rose (Cistus x purpureus hybrid of Cistus incanus and Cistus ladanifer)
Rock rose family -- Cistaceae

April 3, 2015. Los Robles Trail, Los Robles Open SpaceColor: Pink
Non-native

Crete weed (Hedypnois cretica)

Composite or sunflower family -- Asteraceae

May 16, 2015.  Upper Santa Rosa Trail

Seed head

Non-native

Goldentop (Lamarckia aurea) 

Grass family -- Poaceae

May 16, 2015.  Upper Santa Rosa Trail

Non-native

Grass seed

Crete weed (Hedypnois cretica)

Composite or sunflower family -- Asteraceae

May 13, 2015.  Upper Santa Rosa Trail

Seed head

Non-native

Crete weed (Hedypnois cretica)

Composite or sunflower family -- Asteraceae

April 29, 2015.  Upper Santa Rosa Trail

Color: Yellow

Seed head

Non-native

Goldentop (Lamarckia aurea) 

Grass family -- Poaceae

April 29, 2015.  Upper Santa Rosa Trail

Non-native

Grass seed

Goldentop (Lamarckia aurea) 

Grass family -- Poaceae

April 24, 2015.  Upper Santa Rosa Trail

Non-native

Grass seed