Unofficial milkweed field trial

Over the past year, there has been a good bit of publicity and discussion in gardening circles about the efficacy of planting tropical milkweed (Asclepias curassavica) in our butterfly gardens as an aid to Monarch and other milkweed butterflies. There has been research that has indicated that this non-native plant might actually be harming these butterflies and urging gardeners to plant native milkweed instead. 

For the past several years, the only milkweed that I had found available in local nurseries was the tropical kind, and so I had planted it in my garden where it has thrived. It lives through the winter here, although it generally dies back to the roots, and I usually cut it back several times during the year. Cutting it back supposedly reduces the toxins which may cause problems for butterflies, and, if it isn't cut back, it gets quite spindly and gangly and not very attractive. But the butterflies seemed to like it. Maybe because there wasn't an alternative for them.

So, I decided to give them an alternative.

After reviewing my options, I decided to order some seeds from Botanical Interests during this past winter. I planted the seeds of butterflyweed (Asclepias tuberosa) and swamp milkweed (Asclepias incarnata) and started the plants under my grow-lights. 

Most of the seeds germinated and the plants thrived, so by late spring, I had two trays of native milkweed to plant in my garden. I put the plants outside for hardening off and planned how I would monitor both these plants and the tropical milkweed, which was already up and blooming, to try to determine if the butterflies actually showed a preference.

It didn't take long to get the first data from my unofficial milkweed field trial. By the time I went to put my native plants into my garden beds, I found that, in spite of the fact that the plants were still small and had no blooms, several of them already had tiny Monarch caterpillars on them! Meanwhile, all the tropical plants were bushy and healthy and blooming and notably caterpillar-free. The Monarchs had spoken loudly and clearly: They preferred the native plants.

And that has continued to be case. Here is a look at some of my plants today.

This is some of my native milkweed. It all looks like this today. Nothing but stems because the leaves have been devoured by several caterpillars. Actually, it has already started coming back because a few days ago it had no leaves at all. If only the butterflies will leave it alone for a while, it will eventually grow back all the way. Maybe it will even get a chance to bloom.

And here is some of the tropical milkweed, healthy and blooming. These last few days, I have noted a few Monarch butterflies visiting these plants. Once again, until the native plants grow back, they have little alternative if they have eggs to lay. 

There are some Monarch eggs scattered about on this plant. I expect to see caterpillars soon.

My thoroughly unscientific, anecdotal conclusion is this: Monarch butterflies will lay their eggs on native milkweed plants whenever they have that choice. If they have no choice, they'll settle for the non-native plants.

My advice to gardeners based on my findings is to locate native plants or get the seeds and start your own and plant them in your garden. Your butterflies will thank you. 


  1. A very interesting posting, Dorothy. I have several types of milkweed including the native one. We have seen a big decline in the monarch population in the last three years. I am going to further research the role of tropical milkweed. P. x

    1. The bottom line seems to be - as it always is - plant native. But perhaps the tropical milkweed isn't too terrible, particularly if it is frequently cut back and allowed to regrow.

  2. I tried some Asclepias tuberosa this year too. I planted several and most are doing very well and are flowering. However although I've seen Monarchs mating in the garden, and it looked like a female was laying eggs, I haven't seen any caterpillars.

    Interesting that your Monarchs prefer the natives. I will definitely continue to offer a variety.

    1. Obviously, it is a very limited sample, but I can definitely say that the Monarchs that float through my yard seem to overwhelmingly prefer the native plants.

  3. Very interesting. I'm going to order some and see if I have any luck. I have lots of Monarchs in my yard, but all I have is the tropical variety right now.

    1. I think your Monarchs will like the native varieties, K.

  4. Thanks for all the information.
    I have bought butterfly weed plants that bloomed one year, but did survive the winter (I was told they were hardy here). Now I have two plants that I dug up off the side of the road, one of them this year, the other one from two years ago. I am hopeful the newly transplanted one does as well as the older one.

    1. It will most likely do well for you and I'm sure your butterflies will appreciate it.


Post a Comment

Popular posts from this blog

Poetry Sunday: Don't Hesitate by Mary Oliver

Overboard by Sara Paretsky: A review

The Investigator by John Sandford: A review