[Jacqui]

Some people overseas have tried raising their Monarch caterpillars on cuttings of Asclepias curassavica or tropical milkweed, i.e. they have tried propagating new plants from cuttings of the old plant. However, they’ve found that their Monarch larvae don’t like it. Thought I’d share their comments with you all:

Nigel: I never propagate Tropical Milkweed cuttings. It grows so quickly from seed, but apart from that, the cuttings are often more poisonous than the adult plants they came from.

It seems to me, that with many poisonous plants, there is actually quite a
fine line between being a very attractive host-plant to the butterfly
species that feeds on them, and one that is too poisonous for the larvae to
survive on.

So with Milkweeds, all species will propagate from cuttings, but I think it
is generally accepted, that Tropical Milkweed (A. curassavica) is the most
toxic of all.

To me this extra toxicity is not so very surprising, as Tropical Milkweed
is of course native to tropical regions where the Monarchs fly and
reproduce all year. This plant wants to survive too, so after being
continually cut down through feeding it will then put more effort into
producing its cardiac glycosides and less into root growth and leaf growth.

Tropical Milkweed is probably the most attractive Milkweed species of all
for Monarchs to lay on. However, having been eaten down a few times the
adults will still of course lay eggs on it but many hatchling larvae will
die from being over-poisoned. Best always to plant Tropical Milkweed from seeds in my experience!

Zane: We first realized that our milkweed (in 6″ pots propagated from cuttings and then pruned twice to encourage branching) was toxic to many early instar larvae. Each plant was different. Some seemed to be more toxic than others. There was a hort student at UF researching this but he never completed his project. My experience is based on larvae death not on chemical analysis. We next tried plants (from rooted cuttings) that were never pruned and had similar results. Our cuttings were rooted in soil or in a hydroponic system, but once rooted were all grown in soil. Keep in mind that we are USDA Certified Organic so there is no chance of contamination by pesticides. We also were propagating from seed and those plants were more larvae friendly (far fewer fatalities of early instar larvae). Seedling plants that were pruned seemed to have a higher larvae mortality rate than those that were never pruned, but we did not follow that close enough for me to reach any conclusions.

[Pepetuna]

I have never grown Asclepias from cuttings, but I have cut and fed the plant to Monarch caterpillars and never noticed any more deaths after regrowth. What I have noticed is deaths if I feed it to caterpillars that have been on Gomphocarpus previously.

[Jacqui]

Another comment from Ellen in Australia:

We use cuttings from Asclepias curassavica, from necessity. The seeds take 2 years to mature here. Cuttings that have been rooted in water are planted in pots, and the new plants are used to feed late instar cats. They love it. So do I. I’ve just had a second lot of regrowth that’s been eaten this year. The new plants are in the greenhouse, and I saw a Monarch laying eggs on them last week. I normally collect the eggs, to give the plants time to grow.

[Bernie]

I agree with Terry.I use several types of milkweed but have always allowed my currisavaca to regenerate and feel sure that if it had been a problem,I or some of my other friends would have noticed it.

[Terry]

I used Asclepias curassavica exclusively when I used to breed Monarchs continuously back in the early 1990s and never noticed this problem. I used to have Asclepias curassavica planted in deep seed trays and replaced it on a rotational basis in the Butterfly House. Trays of cropped Asclepias curassavica were placed outside to regenerate and replaced by those already recovered. Monarch larvae really can eat enormous amounts of milkweed and I tended to let the stock become very overpopulated which made things difficult on the food supply side. I would be very interested for someone to confirm this theory as fact. I used the method mentioned above for a year and a half so that’s many generations and no real problems that I can recall. Fascinating nonetheless!

[Author]

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