When we talk about “pollinators” or “wildlife,” honeybees and monarch butterflies are two species that people seem to have heard the most about. Even people who don’t garden know that both species are in trouble and that efforts are being made to help each.
In the last couple of months, however, a couple of interesting things about the monarch and the ways people try to help them have come out. Today and Monday I will look at each one–trying not to get controversial about it–so that people can be informed.
Today I want to look at ascelepias–milkweed. We know that monarch butterflies need to lay their eggs on the milkweed plant and their caterpillars need to eat milkweed in order to live.
So in order to help the monarchs, gardeners have been encouraged to plant milkweed, and here’s where the problem begins.
As you might already know, there are many different varieties of milkweed. They are all asclepias, but depending on the variety, they can be “native” or “tropical.” And that’s where the problem began.
In some parts of the country, the tropical variety, asclepias curassavica, is more “common,”–or at least more readily available–than native varieties so gardeners planted those. (It didn’t help that a. curassavica is really pretty.)
Unfortunately caterpillars that feed on tropical milkweed are also eating fungal spores. They pass these on to migratory butterflies on their way up from Mexico and the population is weakened in the process.
It’s a lot more complicated than I have made it seem here. To read an in-depth study by the Xerxes Society, go here.
The takeaway from this: when it comes to asclepias, native really is best.
Oh my! This is all so complicated, and it gets more complicated all the time. Gardening for pollinators is such a fad here, but there is no concern for the ecosystem. People just want to bring the butterflies to their gardens because they are pretty, but are not really aware if feeding them is actually helping them. I have mentioned many times that all the swarms of monarch butterflies that swarm the blue gum and red gum eucalyptus trees south of Monarch Grove in Los Osos are being diverted from native species that rely on them for pollination. No one seems to get that.
I think it’s even more complicated than all of that. There are 2 populations of monarch butterflies and yours is the Western and it is in even more trouble than our eastern population.
But of course you are so right about what people plant for “feeding ” the butterflies. Here everyone plants buddleia, which isn’t the best plant either. It’s not invasive for us–in fact, in my ridiculous northern climate, if you cut it back in the fall, it dies–but it’s surely not the best butterfly plant either. And it does nothing for larva of any sort.