Every month, I try to attend a webinar on monarchs. This month’s webinar was titled "Milkweed and Floral Resource Availability for Monarchs in the U.S." It was based on an eight-year study with the Integrated Monarch Monitoring Program. Honestly, some of it was way above my head. So, why did I decide to write about it this month? Webinars or lectures tend to focus on monarchs and their relationship with milkweed or how pollinator gardens need nectar plants. What was novel about this study was its exploration of the connection between flowering plants, milkweed, and monarchs.
When we stop and think about it, it seems obvious. Monarchs are butterflies that need nectar for energy, which means flowering plants. The female then needs milkweed, the host plant for the monarch caterpillar, to lay her eggs on. So, of course, you need both flowering plants and milkweed to attract monarchs to your landscape. Yet, I have customers who come in specifically to buy milkweed to help the monarchs. A few months later, they tell me the milkweed looks lovely, but they haven’t seen any monarchs. When we discuss what else they have in their landscape, it’s not uncommon for the answer to be cacti, agaves, and rocks. This might be a beautifully designed landscape for humans but not for butterflies. Sometimes in our busy lives, we get rushed and forget some of the basics. I thought this was a good time for a refresher and to share some interesting information I learned!
I really loved that this study didn’t only look at the Eastern Monarch population but also addressed us here in the West. It even included data about the Coachella Valley! This is significant because, in the U.S., monarchs are split into two populations: East and West. When we read or hear about monarchs in the media or studies, it’s generally about the Eastern population. Understandably, the migration from Canada to Mexico is crazy impressive! But this means that, unfortunately, Western Monarchs don’t get much attention. Many people don’t even realize they exist!
In the 1980s and early 1990s in California, the monarchs were in the millions! By 1997, 100 sites were surveyed to count the Western Monarch population, and just over 1,200,000 butterflies were counted. In 2020, at 250 sites, we only counted 1,647 butterflies. In our latest count at Thanksgiving 2023, volunteers surveyed 250 sites and counted 200,000 butterflies. Because of this serious decline in the overwintering population, there are goals to add 50,000 acres of habitat. This would include both nectar and milkweed resources.
More data was needed to understand why the monarch was in decline. There needed to be tracking of the progress of putting habitats on large landscapes. There needed to be a better understanding of where to best support more monarchs. In 2015, a group of scientists formed the Integrated Monarch Monitoring Program. When those scientists met, they had questions: Where is the milkweed growing - or not? What types of landscapes is it growing on? Roadsides, agriculture, developed or protected spaces? What spaces were the monarchs using? And where were the best spaces to target their efforts?
A few interesting things from these studies for us locally: They visited 74 sites in the low desert. The three milkweeds they found were Asclepias subulata, Asclepias erosa, and Asclepias albicans. Asclepias subulata, or Rush Milkweed, was the most predominant, which is not surprising. I was happy to see the amount of the other two, though. Here at the nursery, we are working on propagating both of those and hope to have them available for sale soon!
The scientists also noted the native plants that were predominant at the sites where they found milkweed, giving us more information about plant communities. I’ll be updating the plant lists with this information and we can use it to help design wildlife habitats! But here is a sneak peek of the 10 plants found most commonly with milkweed:
1. Larrea tridentata - Creosote
2. Ambrosia dumosa - Burrobush/White Bursage
3. Bebbia juncea - Sweetbush
4. Condea emoryi - Desert Lavender
5. Chorizanthe rigida - Rigid Spineflower
6. Erigonum inflatum - Desert Trumpet
7. Ferocactus cylindraceus - Compass Barrel
8. Opuntia basilaris - Beavertail
9. Senegalia greggii - Catclaw Acacia
10. Encelia farinosa - Brittlebush
There are things I found interesting or that made me want to research more and questions I had:
Non-random sites are not representative of the natural landscape. Non-random sites were generally managed sites versus random sites which were natural wild landscapes.
Milkweed on random versus non-random sites were different varieties. Should we be doing a better job of planting native milkweed on managed sites?
The density of milkweed was able to be explained by the study parameters. This means we understand where milkweed grows and are able to recreate the habitat.
Monarchs were more frequent where water features were within 340 meters. Reminder to keep a water source for drinking and puddling.
Right of Ways (roadsides) have untapped potential. Just add nectar plants.
Monitoring managed sites can track changes to better our understanding of habitats.
I hope that you found this helpful and interesting. Maybe it made you want to research a bit more on our Western Monarch! The monarch population needs our help. We are capable of making a difference in our backyard habitats and public spaces. We need to be better stewards of our environment because monarchs are just one of many species that need our support. We can do better. I have faith in us!
