Helping the Monarch Butterflies Here in Conejo Valley

“…if we do our part by restoring the habitat, planting Monarch waystations and managing our land differently, Monarchs will do theirs to keep the magic alive.”    Loudoun Wildlife Conservancy

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Monarch Butterflies in Western North America overwinter in California.  In fact, here in Sycamore Canyon School, we are within 10 miles of an overwinter site.

Click here for locations to see overwintering Monarchs in California.

Over the last decade, the monarch population has declined by over 97%.


A major factor contributing to this decline is habitat loss. Monarch caterpillars feed only on milkweed, and fields where locally native milkweeds once grew are being lost to development and agricultural practices.

We can HELP by planting LOCALLY NATIVE MILKWEEDS in our garden!

Locally native Narrow Leaf milkweed

Locally native Narrow Leaf milkweed

Q: What is the locally native milkweed for Conejo Valley?

Narrow-leaf milkweed (Asclepias fascicularis).  You can actually spot these plants when hiking along our local trails.  California’s narrow-leaved Milkweed has a three foot tall stem and large (but narrow) five inch leaves, and a five inch or so flower cluster.  It is a herbaceous perennial that dies back to the root each fall-winter.  Plants have a deep, sturdy taproot that allows them to re-sprout, grow and flower during the warmer months.  A single plant will produce more stems each season.

In our area, new foliage typically doesn’t appear until the weather begins to warm up in March.

Q: Why is planting locally native milkweed so important?


Monarch butterflies eating nectar from narrow-leaf milkweed flowers

Monarch caterpillar feasting on locally native Narrow Leaf milkweed leaves

Monarch caterpillar feasting on locally native Narrow Leaf milkweed leaves

Milkweed is an important plant in the web of life. It  serves both as a nectar plant (providing high quality nectar for the butterflies and a variety of other pollinators), as well as a host plant (providing the ONLY food source for the Monarch caterpillars).

Locally native milkweed grow in sync with the seasonal pattern of our local climate.  The milkweed sprout, become dormant, and then grow back at the right time – when monarchs have returned to the area.

Non-native species milkweed, however, do not behave like the locally native species.  Planting the wrong species of milkweed might actually be harming, rather than helping, the Monarchs.

Asclepias curassavica (tropical milkweed, Mexican milkweed, redhead, scarlet milkweed), a non-native species – leads to unseasonal breeding and incubation of parasitic spores, which increases monarchs' risk to disease and reproductive failure.

Asclepias curassavica (tropical milkweed, Mexican milkweed, redhead, scarlet milkweed), a non-native species – leads to unseasonal breeding and incubation of parasitic spores, which increases monarchs’ risk to disease and reproductive failure.

This is because:

  • Non-native milkweed grow out of season.  In winter, the smell of milkweed plants wake monarchs prematurely from winter hibernation, leading to unseasonal breeding and disruption to the reproduction and migratory cycle.
  • Non-native species (like the tropical milkweed readily available in commercial markets, shown on the left column of the blog) do not senesce (die back) in SoCal’s mild winters.  They grow throughout the year, and by doing so they foster the propagation of the dreaded protozoan parasite Ophryocystis elektroscirrha (OE) to the Monarchs.  OE linger in spore form on milkweed leafs, and continue to spread its debilitating infection to newly hatched caterpillars when ingested by the caterpillars.
Monarch caterpillar infected by OE

Monarch caterpillar infected by OE

Native milkweeds senesce in winter and regrow in spring.  This senesce process kills the OE spores.  The new growths are clean and free of OE spores, breaking the vicious parasitic cycle.

Monarchs that emerged out of season, or infected by parasite, do not usually survive. Even as survivors they are unhealthy and inferior in size and weight to that of a normal, healthy monarch.  Sick monarchs among the population endanger the specie’s long term survival.  For that reason, we strongly recommend plant only the locally native milkweeds.  Although native milkweeds may be harder to find and slower to grow, once established they will raise healthier caterpillars that metamorphosis to strong adult butterflies that will migrate in the proper time.

To avoid purchasing the tropical milkweeds when buying milkweed plants for your garden, remember this little rhyme:
Blooms pink or white help monarchs take flight.
Blooms orange and red help disease spread.

Q: I want to plant milkweeds in my garden.  Where can I find locally native milkweed plants?

First – a warning: Beware of purchasing milkweeds, especially from big box stores, unless you’re certain that the milkweeds haven’t been treated with insecticides called neonicitinoids (neonics).  The insecticides are systemic — they affect every part of the plant. The plant may look strong and healthy, attractive to a potential buyer (you) eager to help out the butterflies.  But when caterpillars eat treated leaves, they fall off the plant within minutes, curl up into a C shape and slowly die.  When buying milkweeds, please ask if the plants are treated with systemic insecticides before the purchase.

Native milkweed plants can be difficult to locate.  Native plant nurseries with plants used to restore natural areas is a great place to start. Internet purchase of milkweed seeds is available from multiple vendors, but available native seed may be of non-local origin. Please ask prospective vendors for information about seed origin.

Q: How long does it take for the Monarch to grow?  And when can I expect to see Monarchs here at Conejo Valley?


There are four generations of butterflies In the span of one year.  Here in Conejo Valley, due to the proximity to an overwintering site, we are in a fortunate and unique position to witness both the emergence of the 4th generation as they head off to winter hibernation, as well as the start of the 1st generation, as the butterflies begin their annual spring migration to the north.  In other words, we can expect to see Monarchs in our garden for 50% of the year!

Life Span of Monarch Butterflies

Generation 1:  2-6 weeks

Generation 2:  2-6 weeks

Generation 3:  2-6 weeks

Generation 4:  6-8 months!

Approximate Time Table for Monarch Butterflies Presence in Conejo Valley

(based on observations made in the SCS Garden)

Conejo Time Line - MonarchQ: When can I plant my milkweed seeds?  How do I plant my milkweed seeds?

Narrow-leaf milkweed is quite easy to grow.  The best time to sewn the seed is Fall. Here’s how:

  1. Select a sunny spot in your garden (minimum 4 hours of direct sun, longer the better).
  2. Wait for a good rain (if no rain, you can wet the selected spot with water).
  3. While the ground is damp, lightly rough up the soil (you can use a gardening hand tool like a cultivator or a trowel).
  4. Scatter seeds directly into soil.
  5. Use the rough up soil to lightly cover your seeds.
  6. Water periodically if there is no additional rainfall throughout the reason. If there are rainfall you can just leave the seeds alone to sprout.

Narrow-leaf milkweed can tolerate most local soils, from sandy to clay, including some pretty awful coastal clay that are acidic in winter and alkaline in summer.

High mortality seems to occur with plants in pots; milkweed species don’t overwinter well in pots, and they often don’t re-emerge in the spring.

Young narrow-leaf milkweed plants like plenty of winter/spring moisture and can even tolerate winter flooding. Irrigate the first year will improve survival.  By second year the root system should be well enough established that the plants will survive on their own.  If you choose to irrigate past the first year of growth, occasional watering in Summer is fine.  Taper off watering in Fall as this will allow the plants to enter dormancy, and reemerge in Spring as strong healthy plants.

Q: What are some common insects we see on the milkweed?  Are they harmful?

Narrow-leaf Milkweed is an excellent insect habitat plant.   Its nectar provides food for butterflies, bees and wasps. In our area, the seed pods are eaten by the Large/Common Milkweed Bug (Oncopeltus fasciatus). The foliage is eaten by a range of interesting insects including true bugs, beetles and larva (caterpillars) of the Monarch and Striated Queen butterflies.

Monarch and Queen caterpillars are voracious eaters. Milkweed plants can look very ‘eaten’ by the end of the summer, but that’s a normal consequence of a healthy ecosystem, and the milkweeds will re-grow the next season, bigger and stronger. The caterpillars, which are well camouflaged, are also protected by the chemicals (cardiac glycosides) produced by Milkweed plants. These chemicals are toxic to many insects and larger animals, including humans. The caterpillars, which are immune to their effects, use these chemicals to deter their predators.

The red and black Milkweed Bug, and the yellow Milkweed Aphids (Oleander Aphids)

The red and black Milkweed Bug, and the yellow Milkweed Aphids (Oleander Aphids)

One particular insect, however, are destructive to the milkweed plants.  The bright yellow ‘Milkweed Aphids’ (Oleander Aphids; Aphis nerii), are not native.  They suck the sap of milkweeds and can decimate the milkweed plant. It is important to remove and dispose of the aphids at first appearance or they will quickly infest the entire plant, making it difficult for monarchs to use the plant.

Below are some methods more friendly to caterpillars and the butterfly eggs while eliminating the aphids from the milkweed plants:

*  Use natural controls such as the Ladybugs that you can purchase in gardening stores.  Just keep in mind that natural controls such as Ladybugs will also eat butterfly eggs and young caterpillars, but will likely feed upon the smaller sized aphids first.

*  Cut and discard infected sections of the plant.  Take care to relocate existing caterpillars by placing a leaf in front of it and give it a gentle nudge on the rear end.  The caterpillar should walk forward to the leaf to allow the relocation to take place.  For your safety and theirs, never handle a caterpillar with bare hands.

*  Hand rub off (yes, that is another way of saying “squish”) the aphids (careful not to rub off a caterpillar or butterfly egg as well).  You may want to wear gloves for this task as it can be high on the yech factor.  Another option (lower on the yech factor) is to wrap duct tape around your hand (sticky side facing out), and tap the infected area to pick up the aphids.

When dealing with milkweed aphids, patience and diligence is key.  Frequently check your plants for signs of the aphids, and if spotted, immediately and carefully remove the aphids to stop the spread.  Early prevention is your best defense.

Click here for the USDA Plant Guide on Narrow Leaf Milkweed

Can’t find your questions? Click here and ask us. We might be able to help! Butterfly humor

2 thoughts on “Helping the Monarch Butterflies Here in Conejo Valley

  1. Pingback: Build a Butterfly Garden and They Will ComeThousand Oaks Green Scene

  2. Pingback: Week of the Pollinators – Part I – The SCS Garden Project

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