Transition Studies in  Flowering Plants 
by Rolf Baumberger

Santa Susana Pass Transition

Diplacus longiflorus    --t-->  Diplacus rutilus

Stoney Point Park - Jamie holding  D. rutilus in hand

A worth seeing transition zone has formed along the Santa Susana Pass.

If you want to see them, go first to Stoney Point Park and look around (A). In the shadow of the stone blocks grows Diplacus rutilus (It starts flowering from the middle to the end of April). Then head west on the Santa Susana Pass to the South (B) car park.

From there you walk back to the gate (C) and go to the circular route. At the height of (D), you will see a series of Diplacus plants in transition. TZ= current transition zone is moving to the West.

34.267222, -118.623056

If you head back and hike to the hummingbird trail, you will see yellow flowering D. longiflorus (E) there. The transition zone is currently between A <----> B. It moves slowly to the west.

Here you can mark individual plants permanently and monitor these over time (3-5 years). See if they change phenotypically or not. Both trails are open to the public. 

  • 940-18
  • 940-19
  • SSP1-
  • Stoneybud
  • Rut01
  • Rut02


Diplacus rutilus grows mainly in the shade of large boulders in this dry landscape. It turns out that the branches of this plant are finally shortened, and the bush takes on a spherical shape. The transition takes about ten to fifteen years. D. rutilus develops from Diplacus longiflorus plant individuals (color phase space).