The Tropical Milkweed
Where I grew up, the common milkweed, Asclepias syriaca, was part of my environment. I was used to big plants like this
and large pods like this
(My Platonic Ideal Milkweed is shown in a copyrighted image here, under Asclepias syriacea.)
Imagine my surprise when a visiting botanist pointed out the “blood milkweed” – a delicate red and orange flower reminiscent of Latana (and more on that similarity another time) – in my own back yard.
With a botanist at hand, there was no problem identifying this plant: Asclepias curassavica, the tropical milkweed, of the family Asclepiadaceae. I will work up the characteristics of the plant that make it a member of the Asclepiadaceae shortly, but first a mention of the most famous relationship milkweed has with an insect – the Monarch butterfly.
I’ve drawn much of my information about this relationship from the Monarch Butterfly Fact Page. Female Monarchs lay their eggs only on milkweed plants, attaching about 400 “clear green oval eggs” to the underside of a leaf. The caterpillars
emerge a few days later. In the United States, east of the Rocky Mountains, these caterpillars mature into butterflies so quickly that several generations will be produced in early to mid-summer. The generation that emerges in late August, though, will live eight or nine months and will migrate to Mexico. At the end of their life, the Monarchs will reach sexual maturity and will migrate back to the US, mating all along the migratory route.
No other butterfly in the world migrates like this. They often migrate to the same exact trees to which their ancestors (several generations ago) migrated last year.
Other than their spectacular migration behavior, Monarchs are known for being repulsive to predators. I remember a famous picture in a college textbook of a Blue Jay throwing up after having eaten a Monarch butterfly. The bright colors of the Monarch will help birds remember not to eat that butterfly again.
Now I’d like to look at the Milkweed Family, Asclepiaceae. The family is named for the Asclepias genus, which in turn is named for Asklepios, the god of healing in Greek mythology. Milkweed roots have been used medicinally in the tropics for pain relief and for the treatment of scrofula.
The common name for the family, Milkweed, refers to the white latex mentioned earlier. This production in combination with simple opposite leaves with no teeth on their edges are good markers for the family.
The flowers, though, are unusual enough to make many members of the family recognizable on sight. As Elpel describes it, there are 5 separate sepals, 5 united petals, and a “corona” (like a crown) that looks like an extra set of petals. The corona consists of 5 hood-like forms facing toward the center of the flower. Inside the corona are 5 stamens fused to the ovary. In A. curassavica, the crowns are yellow and the petals are a red-orange color.
These flowers also have some features, which I’ll not describe, in common with orchids, although the two families are not related. (Note the ants in the image above. They are robbing nectar!) You can find excellent copyrighted illustrations that label of all these parts at Digital Flowers.
The fruit is that famous milkweed pod loved by children because silky threads are attached to the seeds inside. In this image, you can see a pod in front of the inflorescence, and a developing pod behind the inflorescence:
So my checklist for this family is: 1) simple opposite leaves with no teeth on their edges, 2) milky latex in stems, 3) complex flowers with crowns.
My final question is whether Monarchs like all flowers of the Asclepias genus equally or whether, the “common milkweed,” A. syriaca, is the Monarch’s favorite. Naturally, having grown up with the common milkweed, I assumed that was the best for the butterfly.
Luckily, I’m not the first to have had that thought. Some students from Willow Creek Middle School and Century High School in Rochester, MN, had a similar question. They went beyond my simple question, though. They raised 100 Monarch butterflies from eggs, 20 on each of 5 different species of Asclepias. They found that larvae fed on the tropical milkweed (A. curassavica) had the highest survival rate and the shortest time to pupation. The common milkweed was in the middle. So much for my provincialism!
What remains is for me to spot a Monarch on my plant, or even a Monarch migrating. It won’t be one that has migrated from the United States. Central American Monarchs migrate between the highlands and the lowlands only, and they migrate according to wet and dry seasons.
Ready when you are, Monarch!
Your information on the Tropical Milkweed is wonderful!
I just purchased some Tropical Milkweed plants for my garden in Florida. I noticed that the label on the containers identified them as Asclepias curassavica, however, the nursery where I bought them was calling them Butterfly Bush and/or Butterfly Milkweed—the latter is Asclepias tuberosa L., a native of the county in which I live. I went on the internet looking for Asclepias curassavica and couldn’t find them anywhere until I hit on your site. It helped me very much!
Sylvie,
Thanks for your kind words. I hope you enjoy growing the plant. It hasn’t flowered much here in my backyard where it’s growing wild. I’m trying to keep the machete-wielder away from that area, so I can see it bloom again next January-February.
It’s a lovely plant – the colors are spectacular together.
Bo – Thanks.
I just visited your blog, Seeded Earth – filled with beautiful plants and pictures. Here’s the link for anyone who wants to take a look:
http://gardengrow.wordpress.com/
About two month ago, I took some cutting from a Tropical Milkweed that was growing in a canal in North Dade Miami and I started rooting them in water in 2 weeks my first cutting with two 1/2 in roots, I placed them on a cup with dirt. and a week later I took it outside start to aclimate them to the outside. They were out there for short of a week.
A few days ago in the afternoon, I saw a Monark flying around and flierting with the cutting but never sat on the leafs long enought. I saw it go back and forward and fly around it for about 15 minutes… Finally I think she left or I went inside (I can’t remeber) or both.
Today about 5 days later I go and look at the plant and I saw some holes on the leafs. When I look under the leaf, I saw some very very tiny caterpillers, about 5 of them. They can not be very big I almost didn’t notice them. Some are smaller and appear brownish and the two bigger are a little greener. The plant is about 7 inch tall, and it has a total of 8 leafs different sizes and two sets of 4 each flowers and some more growth of leaf inbetween the flowers.
Would this be monark caterpillers?I don’t remeber ever seeing them. These seem so tiny (almost unnoticable) and there seem to be not many leafs for this plant for the caterpiller to survive. Unless the inside leafs start growing very quickly.
Do you think the might be cats from a monark? or do other smaller butterflies lay eggs on Tropical Milkweed? and will the plants put out those leafs fast enought for those caterpillar to eat and survide to butterflys. I imagen
Hi Carlos,
Thanks for noting your interesting observations. I don’t know the answer to your questions because I have yet to see a Monarch butterfly in our Tropical Milkweed plants here in Panama.
Keep up the observations and I hope you find the answer yourself.
Mary
Actually they did turn out to be monarc caterpillers. I had to run a buy larger plants and since I have had about 3 generations of about 20+ larvas survive become pupas and become butterflies. I am surprised that in Panama you have had no ativities. I am getting attached by monarc from every which way. Some time I have to take my milkweeds and hide them away from the yard. The last time all 6 Tropical milkweed I have were eaten to the bare trunk and they are now getting new growth, but I have had to scare the monarcs away to keep them from laying more eggs on my plants. I can only guess that there is a lack of milkweed in Miami Florida or else they wouldn’t be so desperate to lay on my milkweed. I have not been able to get them to flower because the monarcs ate the whoooooooooole thing!!!.
I found another site that is excellent and the prices are very resoanble. They seem to be a non profit foundation of some kind to gain more milkweed for monarch survival. They will provide seeds and small cutings that will become big pants with in short month.
My problem have been the heat of Miami. I have need to plant this pants in part shade until they get established. One need to watch the plants close for wilting here in Miami until they get stablished. Also if one waters them every day, the Milkweed will only grow very shallow roots never or very slowly planting their roots very deep in the soil looking for water. If the roots are too shallow not only they do not stay up too well but they take longer to stablish because they do not gaing to the deeper roots they will need to survive.
http://www.livemonarch.com
I have had several generations of caterpillers and monarch butterflies since my first post a few month ago. A total of about 50 butterflies altogether.
Carlos,
Thanks for this information! You’re doing great work, despite the Miami climate. The Live Monarch site is a fine resource.
Thanks again.
Three years after you first posted, I am finding great information on your site. I love monarch butterflies. I live in Ocean County, NJ, and like you, as a kid I was used to the tall common milkweed with large pods. I am not aware of ever having seen the flowers, though–I guess I didn’t notice them till the fascinating pods developed with their silky “parachutes”! When my husband and I visited the nature center in Cape May, NJ this past spring, they were re-planting their rain garden and had many more common milkweed plants than they needed so they allowed my husband to dig up two of the plants. We have a very shady garden (thanks to our neighbors’ trees!) but we planted each plant in the two sunniest spots we could find in our backyard gardens. One plant died quickly. The other bloomed very nicely but later looked kind of powdery and sickly. I was surprised that the plant really didn’t grow much in height and was pretty short, maybe two feet tall. I was further surprised yesterday, when I found a similar common milkweed plant in one of my front gardens! I realized that until lately I really had no idea what the leaves or flowers of the common milkweed look like, and I have probably had them growing before in my garden without realizing it! My question is: Since these plants are perennials, will they grow a little taller each year, till they are tall enough to support the big pods I am used to? Thanks for your help.
Mary, Thank you for your interesting comment as well as for your kind words. I’m not sure that I can answer your question about whether your plant will continue to grow. As you probably know, individual plants in the species can reach 6 feet in height, but height depends on so much – fertility of the soil, rainfall, sunlight, competing species in the area, and so on. I have the vaguest recollection from my childhood that I did see individual plants taller from one year to the next, but my memory is probably the most unreliable thing in the universe. The nature center in Cape May could give you a much better answer than I can, so next time you’re there, be sure to ask. And post the answer here if you have a chance!
Great idea. I will ask, the next time we are in Cape May. It’s a distance from us; it could possibly be a day trip, but I find you need to stay at the very least overnight to have time to do much of anything–and a two-night stay is even better! There are many wonderful Victorian bed-and-breakfast inns in Cape May, and I would love any excuse to go back to one of them! ;- ) If I get an answer, I will definitely post it. Re: growing conditions for the common milkweed, it seems to me they grow taller and better when they are growing untended in some weedy field, but I could be wrong about that.
Hi, me again. I got the “brilliant” idea of calling the director of the nature center–she was the one who gave us the milkweed plants. Well, she told me various things. One is that the same species of plant WILL grow to different heights, depending on so many things such as sunlight, soil condition, etc. Sometimes the tap root can get blocked by a rock or a clay layer in the soil, and that can stunt the growth. (Also, my husband only took as much of the tap root as he could get, which wasn’t the entire piece; that could stunt it until the root has a chance to grow more.) She did encourage me not to give up on my milkweed plants. She told me that they also reproduce vegetatively, as well as by seed, so next year I should have a few more milkweed plants near the ones that are already there. She said that even the one that apparantly died may still have live roots that will come up next year. So…here’s hoping! I do so much want to attract Monarch butterflies to my garden and provide them what they need in order to reproduce.
Great information, Mary, and thanks very much for getting back. Good luck with your plants – it does sound like you have a good chance for success. Thanks again! Mary