In the United States, we have two monarch butterfly population groups with the Rocky Mountains serving as the dividing line. First, we have a group known as Western monarchs. These butterflies consider the west coast their home. During the summer they live in Northern California, Oregon, and Washington, sometimes even venturing as far north as Vancouver, Canada. These Western monarchs overwinter in coastal areas of Southern California.

The monarch butterflies we see here in northeast Oklahoma are Eastern monarchs. These monarchs visit us twice a year; once in the spring as they migrate north and then again in the fall as they return south to their overwintering site in Mexico. While a variety of insects do migrate, a migration of this great distance is rare in the insect world.

Unfortunately, monarch populations are in decline. As recent as the 1980’s, The Western monarch population was estimated to be around 4.5 million, but by 2015 that number had dropped to about 30,000. It’s come back up a bit, but the overwintering count for 2023-2024 was still only 233,934. That is quite a population drop in just a few years.

The Eastern monarch count happens each year at their overwintering site in Mexico. For this count, rather than attempting to count individual butterflies, they measure the land area that houses the monarchs. During the 2018-2019 season, monarchs occupied about 15 hectares. One hectare is equal to approximately 2.47 acres. This year in Mexico they determined that the entire monarch population occupied only .9 hectares which is less than half of the 2022-2023 number. None of this bodes well for the monarch butterflies.

I mentioned that the Eastern monarchs overwinter in Mexico. One of the more extraordinary aspects of their migration north from Mexico to the United States and Canada, and then back to Mexico is that the monarchs that leave Mexico in the spring are not the same monarchs that return in the fall. They are separated by several generations, and yet they return to the same forest in Mexico each year. There are a variety of videos only showing the overwintering monarchs is you are curious. It is quite a site to see.

There is much debate about the factors that are contributing to the decline in the monarch populations, but one of the primary factors is the decline of natural habitats along their migration paths. These habitats have been diminished or destroyed by agriculture and urban development. When you combine this with our tendency to overuse pesticides, the reason for the decline begins to come into focus.

One thing we can do to help encourage the growth of the monarch butterflies is to plant flowers that not only sustain them on their journey, but also provide food for the baby monarch and there is only one plant that does that. It’s called milkweed.

Milkweed serves as the singular host plant for monarch butterfly larvae so female monarchs search out milkweed on which to deposit their eggs. Once the eggs hatch, they begin to eat the milkweed plant as they are able to devour an entire leave in about a minute. As these monarch larvae eat, they grow to about 2700% of their original weight. For a little bit of perspective, that would be equivalent to a 6-pound human baby eating enough to grow to about 16,000 pounds. That is quite a binge.

Why is the milkweed plant the plant of choice, we’re not exactly sure, but we do know that milkweed plants contain a toxin called glycoside. Because of all this dining on the milkweed plant, monarch caterpillars and butterflies are known to be toxic to predators. No doubt, this trait has contributed to their survival over the years.

Because of this toxicity, you should wear gloves when handling milkweed and refrain from touching your eyes. Also, if you have cats, dogs, or horses, you probably want to avoid planting any milkweed where they might have access. But planting milkweed plants is a great way to help support the monarch butterfly population.

We sold quite a few milkweed plants in our annual plant sale. If you ordered some from us, you’re all set. If you didn’t, you should be able to find milkweed plants at local herb festivals or farmer’s markets.

If this semi-toxic plant is not your thing, you can still support not only the monarch population but also the local pollinator insect population by planting a variety of nectar producing plants. Native plants are always a good choice, but we have recommendations on our website (www.tulsamastergardeners.org) in the Lawn and Garden Help section under the flower section.

To learn more about monarch butterflies and how to support them you can visit monarchwatch.orgwhere you can also learn how to become a certified monarch waystation. Xerces.org also has a lot of good information.

You can get answers to all your gardening questions by calling the Tulsa Master Gardeners Help Line at 918-746-3701, dropping by our Diagnostic Center at 4116 E. 15th Street, or by emailing us at mg@tulsamastergardeners.org. Photo: OSU Agricultural Communications