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What Monarch Butterflies Need | Los Angeles Times

March 5, 2021

[Posted by Chuck Almdale. Thanks to Travis Longcore of LAAS for additional information.]

You can Guide Monarchs Back to their Throne
Numbers in the West have Plummeted. Here are 7 Things Gardeners Can Do.

New York Times | Jeanette Marantos | 27 February 2021

The Los Angeles Times had a full-page article on Monarch Butterflies in their Feb 27, 2021 Saturday section. If you’re at all interested in Monarchs – how are they doing, what’s good for them, what’s bad, and so on — I highly recommend it. You’ll almost certainly learn something new. Click on the link above.

If you’re not sure you want to read the original, I’ve listed a few factoids and excerpts below. Perhaps they’ll pique your interest and you’ll read the original. There’s a lot you can do to help the Monarchs, and they really need our help.

Monarchs breeding in the western U.S. migrate to coastal California. They overwinter in a few locations from Mendocino to Baja. They don’t go to the central highlands of Mexico.

They’re on the verge of extinction. Habitat destruction, insecticides, herbicides — and our good intentions, all contribute to their vanishing.

Eastern Monarchs dwindled from 384 million in 1996 to 60 million in 2019 — an 84% decline. Western Monarchs dropped from 1.2 million in 1997 to 30,000 in 2019 — a 97.5% drop. The 2020 24th Western Monarch Thanksgiving Count yielded only 1,914 butterflies total — a 93.6% drop from the prior year.

Pacific Grove, a famous Monarch Winter sanctuary, saw a decline from 45,000 butterflies in 1997 to none in 2020.

The showy Tropical Milkweed (Asclepias curassavica) you have in your yard may be killing them. Most SoCal nurseries have only tropical milkweeds, which bear feathery purplish-green leaves and deep orange flowers.

Tropical Milkweed doesn’t die all the way back during winter in SoCal, as does native milkweed. That permits protozoa parasites (Ophryocystis elektroscirrha) to multiply on the plants. When the caterpillars hatch, they eat the protozoa along with the leaves. Scientists believe that when a caterpillar eats too many such protozoa, it sickens and weakens the adult monarchs, interfering with their migration patterns, mating success, flight ability and lifespan. Milkweed blooming during winter may also disrupt their migration patterns.

Travis Longcore of Los Angeles Audubon Society and Urban Wildlands Group says that cutting tropical milkweed right down to the ground and keeping it trimmed until April will kill any overwintering parasites.

Here’s seven things you can do, with complete explanations in the LA Times article:

  • Grow Native Milkweed
  • Make Sure It’s Organic – they won’t have systemic pesticides in them
  • Lobby Your Garden Center – to carry Native Milkweed, not Tropical (or Mexican) Milkweed
  • Plant Lots of Nectar Flowers – the butterflies eat nectar, caterpillars eat only Milkweed leaves
  • Don’t Try to ‘Rescue’ Monarchs – raising them indoors doesn’t help
  • Keep an Eye Out – The Xerces Society wants photos
  • Don’t Use Pesticides or Herbicides

All data below is from
The Western Monarch Thanksgiving and New Year’s Counts are the product of annual monitoring efforts by volunteer community scientists to collect data on the status of monarch populations overwintering along the California and Northern Baja, Mexico coast (and a few sites from inland areas of California and Arizona). Thanks to the extraordinary efforts of these volunteers, we have 24 years of data demonstrating that monarchs have undergone a dramatic 99.9% decline in the western U.S. since the 1980s. The data collected by volunteers are compiled and entered into the Xerces Society’s Western Monarch Overwintering Sites Database which also includes many historic counts and survey efforts. Contact if you are interested in obtaining a copy of the entire database.

List of Los Angeles County Monarch Butterfly survey sites
In 2020 only 5 of these sites were surveyed and no Monarch were found
List from an data available from

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