SeaVenture Blog

The Return of the Monarchs

Monarchs in Winter

Monarchs in Winter

We’re spoiled living here for lots of reasons, but one of the most amazing is the annual return of a multitude of Monarch butterflies—you cannot look at thousands of these beautiful insects hanging from a tree and not smile. We’ve taken them for granted, but in recent years their numbers have crashed. Their decline is all the more sad because of the incredible journey they take to get here—their migration is almost like magic.

The migrating Monarchs don’t return all at once, like the swallows do, but they do build up fairly quickly into thousands and thousands clustered on the eucalyptus, in the same trees year after year. It’s a really an amazing and beautiful sight that brightens our winters here, and you should make sure you see them, even in their smaller numbers. The Pismo grove is within CA state parks control, and docents give two free talks every day at 11 a.m. and 2 p.m.

The Incredible Story of Monarch Butterfly Migration

One of the most surprising things about the Monarchs is that the ones we see have never been in Pismo before. In fact, they are four generations removed from the butterflies that left the grove to go north last year. You can read a longer version of this story online, but here’s the short version.

Monarch Butterfly Migration Routes

Monarch Butterfly Migration Routes

In late winter, the Monarchs will mate and then leave, stopping at some point to lay eggs in milkweed plants (ONLY milkweed). These butterflies die, to be replaced by the generation hatched from the eggs in the milkweed. Each insect goes through 4 stages of development—egg, pupa, caterpillar, butterfly—with the beautiful butterfly in this generation living only a few weeks as it continues the migration. At the end of its life it starts yet another generation by laying eggs in milkweed.

The single migration cycle of generations is completed when the fourth generation is hatched, eventually maturing into adult butterflies. THIS generation is different than the three before it: it will live 6 to 8 months and complete the return migration to the point in California or Mexico where its ancestors started. These butterflies overwinter in the warm southern climates until the end of winter nears, and the migration cycle starts again.

Where Have All the Monarchs Gone?

Monarch on Milkweed

Monarch on Milkweed

You note in the story so far that the Monarchs and milkweed have a thing going. The dependency of the butterflies on milkweed is almost total, so when milkweed disappears, the Monarchs disappear too.

The milkweed along the migration routes is disappearing. It turns out that farmers use Roundup to control weeds, and the herbicide drifts into milkweed patches and kills that along with other plants. Where there is no food for the ravenous caterpillars to eat, there can be no butterflies.

Right Kind of Milkweed in the Right Place

We know well-meaning people who buy “milkweed” at the

About Monarchs and Milkweed

About Monarchs and Milkweed

local landscaping store and try to “help” the Monarchs out. The thing is, the wrong kind of milkweed in the wrong place can actually hurt their chances. If a California hibernating Monarch lays eggs in local milkweed, it can actually disrupt the migration cycle, putting them into even more danger.

Here on the Central Coast there are friends of Monarchs who are working to preserve the habitat they need to hibernate. But in northern farming areas on both sides of the Rocky Mountains, other people are working to rebuild the milkweed for the migratory generations of butterflies to eat. These activists have been able to get Monsanto, the producer of Roundup, to join the effort to improve and protect Monarch habitat in farming areas.

I sure hope they succeed.


Lauren is a lover of events, the great outdoors, wine, food, friends, and family. With 12 years of wedding experience, she offers helpful insights and pointers for weddings and special events. As a San Luis Obispo local, her tips come from first-hand experience of the beautiful Central Coast.

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