Monarchs in the South Bay

Did you know that several small sites exist locally

where Western Monarch butterflies overwinter? 

Two of these “roosts” occupy branches in protective

eucalyptus and pine trees located along the

Greenbelt in Manhattan Beach and Hermosa Beach.

Long-time locals have noted the annual hibernating

congregations at these locations, in varying

numbers, for over fifty years. 

 

                                                   

                                                   Monarchs and Milkweed

                                                                  Western Monarchs leave their overwintering sites each                                                                           spring in search of a mate and milkweed to lay eggs on.                                                                         The  lucky ones will find local native milkweed varieties                                                                              including Narrowleaf milkweed, Asclepias fascicularis.                                                                              This lovely drought tolerant species, favored for its nectar                                                                        by Monarch adults and leaves by their caterpillars, has                                                                            historically been the most common milkweed species                                                                              throughout California.  It's the easiest to grow and can be                                                                        found in plant or seed form at local nurseries or                                                                                          online retailers. 

 

 

 

 

 

 

CA NATIVE MILKWEEDS ARE DECIDUOUS, dying back to

the ground in winter.  Their absence signals

Monarchs to migrate. 

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NON-NATIVE MILKWEED VARIETIES ARE EVERGREEN,

and their availability compels Monarchs to                                                                                               breed instead of migrate. 

 

SCIENTISTS HAVE DISCOVERED greater spore loads      

of a protozoan parasite called Ophryocystis

elektroscirrha, OE, on Monarchs who do not

migrate.  OE is a Monarch-dependent organism

spread to milkweed leaves by adults carrying the spores.

It can debilitate caterpillars that consume heavily spore-laden leaves. 

 

Although OE has co-evolved with Monarchs, according to Xerces Society, the introduction and popularity of evergreen milkweeds, leading to fewer migrating Western monarchs, may be one factor in the butterfly’s declining numbers. 

 

                                                 Promote Monarch Health

Here is what governments and citizens in the South Bay can do to support the health and sustainability of our local monarch populations: 

 

1. PROTECT OVERWINTERING SITES from pesticides, herbicides, and inappropriate tree trimming

2. PLANT LOCALLY NATIVE MILKWEED (pink or maroon flowers) in home and City landscapes that are 1 mile or more from the coast. Contact a local nursery or check out the “Milkweed Finder” page on Xerces.org for plants and seeds. Generally, these Aspecies are best for Los Angeles: eriocarpa, california, fascicularis and vestita.

3. REPLACE EVERGREEN NON-NATIVE MILKWEED (yellow or red flowers) or cut it way back and ensure there are no leaves throughout winter. 

4. PROVIDE AN ASSORTMENT OF NECTAR PLANTS in addition to native milkweed such as yarrow, sunflowers, seaside daisy, black and other native sages, verbena and manzanita. Their flowers can be accessed by Monarch butterflies for nectar throughout the year. 

 

LEARN MORE from the Xerces Society here: monarchs ​

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