Monarch Migration: Milkweed Matters

Jill Staake

By now,  you’ve certainly heard the news about the dramatic monarch population decline that’s been documented this year. (If not, click here to read SeEtta’s recent terrific post on the subject.) It’s true – monarch numbers are down this year, and there are a variety of factors involved. While weather is partially to blame, another big concern is the lack of milkweed available for monarchs, which is crucial to their survival. To prove that point, let’s take a look at some interesting monarch migration tracking maps from Journey North, a wonderful citizen science website that allows you to help track the migration of monarchs, hummingbirds, whooping cranes, and more.

First, here’s the most recent tracking map showing the progress monarchs moving north from Mexico have made so far.

Note the way the migrating monarchs (represented by yellow and white dots) have funneled right up through east central Texas and into southern Oklahoma. With the exception of a few strays, you can see the very definite migration path they are following. Remember that these monarchs are the so-called “supergeneration”; these same butterflies flew to Mexico last fall and overwintered in the Oyamel fir forests. They are now as much as nine months old (that’s ancient for a butterfly), and their job is pretty much done. At this point, all they want to do is mate so the females can lay eggs on the newly emerged milkweed. Then, this generation will die off, and the caterpillars that hatch from the eggs will, in a few weeks’ time, turn into the butterflies that will continue the journey north. It is absolutely vital at this time for the monarchs to find milkweed, or they will die without being able to create the next generation. So let’s take a look at another Journey North tracking map – this one showing where milkweed has begun to emerge.

Take a close look at Texas, and compare the two maps. Right away, you’ll see how very important milkweed is – where milkweed is found, so are the monarch butterflies. It’s really that simple; monarchs cannot survive without milkweed. This time of year, the milkweed in Texas is absolutely necessary. Monarchs are very weary from their long journey last fall, overwintering on their fat supplies, and then making another long journey north. They don’t have much time left when they get to Texas – they must find milkweed as soon as they can.

The milkweed population is Texas is struggling too; as the name indicates, most farmers and agriculture view it as a weed, and spray heavily to eliminate it from their fields. As milkweed disappears from large swathes of  its natural habitat, the only way for it (and the monarchs who depend on it) to continue is for home gardeners to take up the cause. Here are a few tips:

  • Plant early and often! Monarchs require milkweed all season long. In Texas, monarchs arrive as early as late February (depending on your location), so plan to have milkweed available as soon as spring arrives.
  • Choose the right species. Milkweeds native to your area are best, but be cautious: Common Milkweed (Asclepias syriaca) can be a real beast and take over your whole garden. If you’ve got room to devote to it, then plant some and let it take over. If you find that species to be a bit too much to handle, or if it doesn’t grow in your area, seek out better options. Click here to learn more.
  • Don’t use pesticides. It seems like common sense, but milkweed is susceptible to other pests, including milkweed bugs and aphids. Many folks tell me proudly they only use insecticidal oil – no nasty chemicals for them! – to control these infestations, until I point out that the insecticidal oils don’t discriminate: they kill monarch caterpillars and eggs too. If you have aphids or other pests, hit them with a hard blast from the hose to shake them loose.

Milkweed isn’t the only way to help monarchs survive; protection of their wintering grounds and further study of the extreme weather brought on by climate change are part of the solution too. As a home gardener, though, planting milkweed is the best way you can join the fight and support these beloved butterflies as they make one of the most amazing journeys on earth.

  1. says

    I have bunches of flower beds. Alot of perennals and a few annuals for more color. I spotted mildweed in back of one of our buildings and then a couple in the flower gardens. I have let them go. They really don’t take anything away from the gardens,
    especially when we see the monarchs on them. Now the MIlkweed has hit my road ditches and most all of the gardens. The will stay there. Love seeing the monarchs so the milkweed stays!

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