23 June 2014

Milkweed - the first week

Anyone who has read this blog on a regular basis knows that I have repeatedly decried the sad situation facing Monarch butterflies in the United States.  There's little I can do to alleviate the loss of their winter habitat in the mountain forests of Mexico or to stem the widespread use of Roundup herbicide, but perhaps with a series of blog posts I can inform the public about some of the nuances of growing milkweed - the Monarch's host plant (the only plant its caterpillars can feed on).

At our latitude (southern Wisconsin in the Upper Midwest), spikes of milkweed emerge in early May.  These are growing from deep and well-established root systems that are well-protected from surface freezing temperatures in the winter.  I presume the trigger for cell division is some threshhold temperature or some accumulation of degree-days.  When that limit is reached, the growth is rapid.  The top image shows asparagus-like spears that had not been present the day before.

With an deep-underground branching root system, the spikes can emerge in what appears to be totally inhospitable microenvironments.  This one is coming through an old (probably deteriorated) piece of landscape fabric and past a layer of gravel.  And the early growth is rapid:

This photo was taken one week after the first two.  It's already 6" high and ready to accept Monarch eggs and tolerate the depradations of several caterpillars (Monarchs typically lay their eggs singly, but sometimes two oviposit on the same plant).

In the next installment I'll comment on the perception of the "weediness" of the plant.

Note:  the milkweed shown here is Asclepias syriaca - the "common milkweed."


  1. I sent for and have finally received a packet of milkweed seeds -- is it too late to plant them? I am in western Tennessee and the temperature is in the high 90s during the day and in the high 60s at night. I was planning to plant them in the flower bed in front of my house where they would get full sun in the morning and indirect sun in the afternoon...

    Any tips you can give me will be greatly appreciated. Should I just plant the seeds or should I start the seeds inside and then transplant the seedlings. Sorry for all the questions, but the seed packet has no information...

    1. Here's the relevant page from MonarchWatch:


      And this is the relevant forum at GardenWeb:


      It would not be too late to plant them, and in your climate they should not need an indoor start. Be aware that first year seedlings are much smaller and more fragile than the ones photographed for this post. They will probably stay small all year and not flower, but they are putting down tap roots that will secure their future, more vigorous, growth in subsequent years. The small ones have less of the nasty "milk" and might thus be browsed, so if you can incorporate any rabbit deterrants, that would be good. Also, plant them where you want them to live - they are not easy to transplant because the root goes so deep.

      p.s. - there are lots of kinds of milkweed (http://www.monarchwatch.org/milkweed/guide/index.htm). My comments/suggestions/blog posts apply primarily to Asclepias syriaca - the "common milkweed."

    2. Thank you for the timely and helpful information -- I'll plant them right away!

  2. in Shenandoah the milkweed is already beginning to flower. By July the butterflies are everywhere

  3. Out of the seeds I started in pots 10 have survived and doing well. One did very well in our very wet June but the other species drown. Thank you sending them, they will bring joy for many years to come.

    1. Thank you for the update; I was wondering how they had fared in your Southern climate.

  4. Here in New Zealand, plant shops do a roaring trade in Swan Plants (Gomphocarpus physocarpus, a species of milkweed seemingly different from what you have shown) that the Monarch feeds on.
    Many people enjoy having the Monarch in their gardens and many children have marvelled at the metamorphoses of this beauty
    My family, having seen the voracious destruction of many swan plants by the Monarch caterpillars, have renamed the caterpillars caterpigs.


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