Category Archives: Milkweed

Keeping Milkweed Over the Winter


One way to keep your tropical milkweed plants growing over the winter is to take cuttings in the fall, place them in some water. No – Diet Coke is not used. Over time they will root. I put mine down in the basement underneath some lights and fed them my miracle gro diluted solution. Here’s what the roots look like on February 1st.
















I then transplanted them into some good potting soil. They will definitely be ready for spring.

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Late Season Monarchs and Milkweed

“I took one of your classes at PVNC and enjoyed the tour of your backyard BF garden.  Like everything, my Swamp Milkweed bloomed early, and now is full of milkweed pods.  I’ve seen a few Monarchs flitting around.  One landed on my Eastern Blazing Star.  My question is this…….Will Monarchs find the milkweed without the blooms to lay their eggs?”


Monarchs will find your milkweed without the blooms, but the situation is changing right now – September 16th.

Monarchs are migrating through St. Louis down to Mexico and these “youngsters” are not laying eggs.
There may be a few older monarchs around that still will be laying eggs though, so it’s nice to have some new fresh milkweed.
While Monarchs can lay eggs on older milkweed, they prefer new leaves and plants.

I’d recommend planting tropical milkweed, Asclepias curassavica, next year. I start mine indoors from seed in March.
It’s an annual so you need to save seed every year for next years crop.

Tropical milkweed is blooming now and will attract migrating Monarchs to your yard.
They won’t however be interested in your older non-blooming swamp milkweed.


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Tropical Milkweed – All I Know

Tropical Milkweed, Asclepias curassavica, also called blood flower, is one of my favorite annuals to grow in the St. Louis area.

It’s not only a host plant for monarchs, but is also an attractive nectar plants for the fall migrating monarch butterflies.

It’s hard to find the seeds or plants in most nurseries, so I usually save seed from the prior year. Online sources of seed are listed at the bottom.

I prefer to start my seeds in individual containers or plastic 6-packs.

Outside in the soil in spring, seeds took 11 days to germinate. Inside on a heat mat, covered with a plastic cover, seeds will start to germinate in five days.

TM likes lots of sunshine, so I like to put it in a sunny area with little if any competing plants.

TM takes a while to get growing since it’s a tropical plant, so there’s no big rush in getting the plants in the ground. They also seem to do better in good garden soil.

Here’s an article on milkweed pollination – it’s a very complicated process. I tried to do it myself, but didn’t have any luck.

Besides monarchs, aphids love milkweed. At times you will see your plants covered with aphids. Since I can’t use pesticides, the only way I can discourage them is spray them with water from the hose. Luckily aphids seem to have a limited life-span and they will just disappear if you wait long enough.

There are some different varieties and colors, but they are all basically the same.

1. As the plant gets larger you can cut off the top to encourage branching.  This doesn’t always work.
2. TM will root itself in water if you cut off a big cutting.

Comparison to Perennial Milkweed
While I have tried numerous “perennial” types of milkweed in the past, they have all disappointed me over time. They usually don’t last more than two years.

Online Seed Sources

Swallowtail Garden Seeds

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Milkweed Seed from Everwilde

One of the cheapest places to buy tropical milkweed seed is They only charge $2.50 for 500 seeds and only $2.00 in shipping. They also have quite a few other seeds available so give them a try.

I bought the 1/4 oz size and it’s supposed to have 2,750 seeds. That should keep me busy for a while.

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Aphids on Milkweed – what to do

One of the truths when growing milkweed is that you not only get milkweed, but you also get other bugs which love milkweed – besides monarch butterflies.

Aphids are the main pest, but also you may get quite a few of the milkweed bugs.

Here are some possible solutions:

  • Do nothing – aphid populations will rise and fall. In nature this is just part of the natural process of life. They will eventually draw predators to their location.
  • Before you do anything else check for monarch eggs and larva. You don’t want to injure them.
  • I have found that most aphid populations die off around July 4th in St. Louis. One theory is that the aphids get infected with a disease that kills them off. The aphids are all clones, so if one is infected, the others will should get the same infection. The other theory is that the predator population has built up by this time and controls the population.
  • I have taken to spraying the milkweed with water when I have aphids. My theory is that it might encourage viruses and disease which might kill off the aphids.
  • Inter-planting with cover crops is another solution I have found which worked well. The aphids have a harder time finding the milkweed when it is surrounded by other plants.
  • Flaming the plant bed is another solution I have heard of. You obviously do this before you plant. It should kill any eggs which may have over-wintered. I have never done this.
  • Some “Perennial” milkweeds actually only live 2 to 3 years and then die out. If the plants are not healthy, there’s a good chance they attract aphids. I usually plant Asclepias incarnata and Asclepias tuberosa seeds every fall since they don’t last long in my garden.
  • If everything is clear, you can try a simple blast with a garden hose. They will cling on, but with persistence you can get some of them off your plants. Unfortunately, they seem to find their way back.
  • You can then try a soap and water spray – I’ve tried it and it works. I’m using about 1T dish soap in one quart of water. Most sites say not to do this in hot weather as it hurt the plant. All of the black spots are dead aphids. I have noticed that while the leaves don’t seem to be affected, the blooms whither away with this soap spray, so soap is not quite innocuous as I’d like.
    I won’t do this again.
  • If infestations are terrible, you can simply clip off the infested area and dispose of them.
  • Plant lots of milkweed – I’d suggest 25 or more plants. You want to bring in lots of beneficial insects.
  • My final solution is to use an oil spray made for plants. Again check for monarch eggs and larvae. This will definitely kill the aphids, but will also kill other insects. Having an oil spray on the leaves and flowers where monarchs will lay their eggs is questionable, so I avoid doing this.
  • I generally don’t worry about milkweed bugs unless I get a lot. You then just use a soapy water solution in a container and knock the beetles into the container.
  • It’s interesting to me the many bugs you will find on milkweed. (click here)

Note – as I was writing this I noticed one Monarch egg and one lady bug which just goes to show that you have to be careful when working with pests.

If you want to learn more about aphid reproduction, watch David Attenborough’s Natural Curiosities – Season 2 #1 – Virgin Birth. It’s available on Netflix.

August 3, 2021 – 100 plants and zero aphids.
Here’s an interesting article about specific viruses in plants and soil which might deter aphids.

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Milkweed Seeds

1650 milkweed seeds for $7.00 – now that’s a bargain. seem to be a great and economical source for milkweed seeds.  It works out to be a bit more than 2 cents per plant – it doesn’t get much cheaper than that. Since I’ve been having trouble with milkweed seed pollination, this may be a good alternative after a bad season.

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Milkweed Pollination

After a very poor year of milkweed seeds, I thought I’d try some hand pollination and see if that helps. In many flowers and fruits you can just go around with a small water color brush and move the pollen from one flower to another. With milkweed however, what I’ve learned though is that it’s a much more labor intensive process than I thought at first. You have to hand remove the pollinarium which are two sacks of pollen attached together. Insects like bees get their legs caught in the pollinarium and pull it out when they struggle to get free. Then when they move to another flower, they may insert it into the stigmatic groove on another flower. Here is a link from Monarch Watch which describes the process.

Below are a couple of videos showing the process. I’m wondering if a smaller bee population might be part of the problem. Since swamp millkweed only lives 2 to 5 years I need to come up with a solution for this problem.

Here’s a picture of the pollinarium in the stigmatic groove.

source –

Note – I had one response which said that they use a small water color brush on tropical milkweed and had good results. I’ll test this out also, but doubt that it’s the paint brush doing the pollination and more likely bees.


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Buying Milkweed Seeds

I’ve found a nice source for new varieties of milkweed seeds – Butterfly Encounters. They’ve got fast service, reasonable prices, good directions on their website and around twenty different types of milkweed – perennials and annuals. They did a nice job with my order.

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Starting Seeds in the Frig

Some seeds need cold stratification to germinate. What I always do is to plant the seeds outside and let Mother Nature do the rest. I’ve never had any luck trying to cold-stratify in the refrigerator. I’m going to try the method shown below for the frig. The recipe is this:

1/4 cup dry sand
1/4 tsp hot water
Mix above together in a ziplock back.
Add in your seeds, mix and then close the bag, trying to get out as much air as possible.
Place in the frig for 6 weeks.
Take them out and plant.

Feb. 7th – put four types of milkweed in the frig.  I’m also going to plant the same four types of milkweed seeds outside in the soil and see what difference there is.

April 1st – took the seeds out of the frig and planted them in the basement – covered and also using a heating pad.

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milkweed-oneto23If you’re familiar with the story in the bible where the loaves and fishes were multiplied to feed many people, you can do the same sort of thing with your Asclepias incarnata, Swamp milkweed.

Violets are a bit aggressive in my yard and garden and will take over a garden if allowed to do so. I was digging up some violets surrounding one of my milkweed plants and in the process I was able to divide the milkweed into twenty-three plants. I potted twenty-two and put one back in the original location. I’m not sure if they will all come back, but even if only 50% make it, it’s an easy way to increase your milkweed plant population.

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